Patent Publication Number: US-9407175-B2

Title: Electric control and supply system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a divisional of pending U.S. application Ser. No. 12/569,181, filed Sep. 29, 2009, entitled “Electric Control and Supply System,” which is a continuation-in-part application of each of the following applications: U.S. patent application Ser. No. 10/415,510, filed Apr. 29, 2003 and entitled Control and Supply System, which claims the benefit of PCT application PCT/EP01/12547 filed Oct. 30, 2001, which claims the priority of DE 200 18 560.8 filed Oct. 30, 2000 (1600-08400; OTE-030339); U.S. patent application Ser. No. 10/489,573 filed Mar. 12, 2004 and entitled Universal Power Supply System, which claims the benefit of PCT/EP02/10471 filed Sep. 18, 2002, which claims the priority of DE 201 15 471.9 filed Sep. 19, 2001 (1600-09300; OTE-030452); U.S. patent application Ser. No. 10/489,583 filed Mar. 12, 2004 and entitled Universal Power Supply System, which claims the benefit of PCT/EP02/10468 filed Sep. 18, 2002, which claims the priority of DE 201 15 473.0 filed Sep. 19, 2001 (1600-09500; OTE-030454); U.S. patent application Ser. No. 10/489,453 filed Mar. 12, 2004 and entitled DC Voltage Converting Device, which claims the benefit of PCT/EP01/12547 filed Oct. 30, 2001, which claims the priority of DE 200 18 560.8 filed Oct. 30, 2000 (1600-09400; OTE-030453); U.S. patent application Ser. No. 10/489,584 filed Mar. 12, 2004 and entitled DC Converter, which claims the benefit of PCT/EP02/10469 filed Sep. 18, 2002, which claims the priority of DE 201 15 474.9 filed Sep. 19, 2001 (1600-09600; OTE-030455 US); U.S. patent application Ser. No. 10/276,204, filed Nov. 12, 2002 and entitled Actuating Device which claims the benefit of PCT/EP01/05156 filed May 7, 2001, which claims the priority of DE 200 08 415.1 filed May 11, 2000 (1600-07500; OTE-030295); U.S. patent application Ser. No. 10/276,201, filed Nov. 14, 2002 and entitled Actuating Device which claims the benefit of PCT/EP01/05158 filed May 7, 2001, which claims the priority of DE 200 08 414.3 filed May 11, 2000 (1600-07400; OTE-030297); U.S. patent application Ser. No. 10/344,921, filed Feb. 18, 2003 and entitled Method and Device for Measuring a Path Covered which claims the benefit of PCT/EP01/09513 filed Aug. 17, 2001, which claims the priority of EP 00117841.7 filed Aug. 18, 2000 (1600-07700; OTE-030305); U.S. patent application Ser. No. 10/415,419, filed Mar. 29, 2003 and entitled Actuating Device, which claims the benefit of PCT/EP01/12551 filed Oct. 30, 2001, which claims the priority of DE 200 18 564.0 filed Oct. 30, 2000 (1600-08200; OTE-030327); U.S. patent application Ser. No. 10/415,418, filed Sep. 4, 2003 and entitled Actuating Device, which claims the benefit of PCT/EP01/12549 filed Oct. 30, 2001, which claims the priority of DE 200 18 563.2 filed Oct. 30, 2000 (1600-08800; OTE-030328); U.S. patent application Ser. No. 10/415,696, filed Oct. 30, 2001 and entitled Isolating Device which claims the benefit of PCT/EP01/12548 filed Oct. 30, 2001, which claims the priority of DE 200 18 562.4 filed Oct. 30, 2000 (1600-08700; OTE-030329); U.S. patent application Ser. No. 10/467,112 filed Oct. 30, 2001 and entitled Valve System, which claims the benefit of PCT/EP01/12550 filed Oct. 30, 2001, which claims priority from DE 20012168.4, filed Feb. 8, 2001 (1600-08900; OTE-030331); U.S. patent application Ser. No. 10/415,511, filed Oct. 30, 2001 and entitled Rotating Regulating Device which claims the benefit of PCT/EP01/12554 filed Oct. 30, 2001, which claims the benefit of DE 200 18 548.9 filed Oct. 30, 2000 (1600-08300; OTE-030332); and which claims the benefit of German patent application No. DE 203 11 033 filed Jul. 17, 2003 and entitled Pump Device, all hereby incorporated herein by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The electric control and supply system comprises a supply and control assembly at a first location and a control and actuating assembly at a remote location associated with a remote device. An umbilical extends between and connects the supply and control assembly with the control and actuating assembly for supplying direct voltage to the control and actuating assembly. The electric control and supply system may be used, for example, in the production of oil and gas and may be used either with land based wells or offshore wells. With offshore wells, the supply and control assembly is disposed on a platform or vessel at the sea surface and the control and actuating assembly is located at a remote location below the sea surface such as at the sea floor. The umbilical extends subsea from the supply and control assembly supplying direct voltage to the remote subsea control and actuating assembly. The subsea control and actuating assembly is connected to various electrical devices, such as motors, electrical actuators and similar equipment via appropriate connecting lines. 
     2. Background of the Art 
     Typically, subsea tools (e.g., controls systems and actuators) are hydraulically controlled and actuated. However, hydraulic supply lines are large and expensive. Further, hydraulic equipment, such as pumps at the surface, are large and take up a significant amount of space on the platform or vessel. One way to solve the problems presented by hydraulic equipment is to implement electrically powered subsea tools. Therefore, electrical control and power supply systems for subsea tools are needed. 
     Prior art electrical control and supply systems include an energy supply system at the sea surface, which transmits alternating voltage through a subsea cable to the sea floor. The amplitude and frequency of the alternating voltage is selected such that, for example, the subsea tools connected to the end of the subsea cable receive a suitable supply voltage for their operation. Each subsea tool is connected to a separate subsea cable. Furthermore, data transmission between the surface and the sea floor occurs via separate subsea cables. 
     Referring to  FIG. 1( a ) , there is shown a prior art control and supply system  1  having a voltage supply and control device  3  with appropriate voltage source and multiplexer device  7  arranged above the surface of the sea  4 . The voltage supply  3  transmits alternating voltage directly, via a subsea cable  5 , to a control and actuating device  6  arranged below sea level. The control and actuating device  6  is connected via connecting lines  8  to appropriate electrical devices  2  or electrical units  9 . An electrical unit  9  may be formed by a group of electrical devices  2 , which, for example, are arranged in the form of a tree structure and are controlled and actuated on a common basis. 
     A data cable  10  is provided for the transmission of data and control signals between the voltage supply and control device  3  and the control and actuating device  6 . The data cable  10  is preferably composed of coaxial conductors. 
     Normally, an alternating voltage of a maximum of 600 VAC is transmitted along the subsea cable  5 . For the supply of the appropriate electrical devices with 240 VAC and appropriate power, cross-sectional areas of at least 175 mm 2  for appropriate conductors are required in the subsea cable having a length, for example, of 50 km. 
     The control and actuation device  6  includes at least one motor actuation device  11  and a control system  12 . The various motors, as electrical devices  2 , can be used subsea for the actuation of valves, BOPs (blow-out preventers) and similar equipment used for the production of oil or gas at the sea floor. 
     One disadvantage with prior art control and supply systems, such as shown in  FIG. 1( a ) , is that a costly subsea cable is necessary. For example, to supply a subsea electrical device with 240 VAC via a subsea cable that extends 30 to 50 km from the surface down to the subsea electrical device, the subsea cable must have a cross-sectional area of 100 to 200 mm 2 . In addition, data lines are required, such that the subsea cable must have a substantial diameter, and thus be very costly. 
     In the above example, it has been assumed that 240 VAC is sufficient for the subsea electrical devices. However, it has now been found that higher voltages are required, for example, in order to be able to actuate certain subsea electrical devices, such as servomotors requiring greater power, for example, to close valves in the production of oil and gas in a maximum time period of one minute. Where such electrical devices must be supplied with a greater voltage, the cross-sectional area of the subsea cable increases still further. 
     In addition, it has been found in practice that on starting a servomotor as an electrical device and in particular for servomotors requiring greater power, even with a slow starting process, a return signal is transmitted via a subsea cable to the supply and control device at the surface indicating the starting process of the servomotor as a short circuit at the end of the cable. This leads to the switching off of any systems automatically protected against short circuit. 
     Furthermore, with the previously described prior art control and supply system, the overall system only has an output power efficiency of 27%. 
     Another known control and supply system is shown in  FIG. 1( b )  with the transmission of alternating voltage along the subsea cable  5 . In this case, however, a voltage of a maximum of 10,000 VAC is transmitted which is reduced, before the control and actuation device  6 , by a suitable transformer  13  to the voltage values required for the electrical devices. Also, with this prior art system, a separate data conductor  10  is provided as a coaxial cable or similar cable. The control and actuating device  6  according to  FIG. 1( b )  requires expensive power capacitors  14  in order to smooth the reduced alternating voltage appropriately. In addition, with this prior art system, as with the system according to  FIG. 1( a ) , power factor correction devices are needed to lower the apparent power of the system to obtain an adequate efficiency for the overall system. Such correction devices are very complex and normally quite expensive and consist of capacitors or similar devices. 
     With the prior art system according to  FIG. 1( b )  and for appropriate voltage values and powers for the electrical devices on the sea floor, conductor cross-sectional areas in the subsea cable of, for example, at least 75 mm 2  arise for a length of 50 km or with power factor correction at least a cross-sectional area of 26 mm 2  for a 50 km length. 
     However, even with the complete expansion of the previously mentioned prior art system, the efficiency normally is less than 70% and the cross-sectional areas for a conductor in the subsea cable are about 16 or 26 mm 2  for a length of 30 km or 50 km, respectively. 
     Converting devices have been used to convert a high voltage (DC or AC) to a lower voltage (DC or AC). If a high voltage is present on the input side, a corresponding conversion into another voltage is difficult as a rule because corresponding components of the converting device do not show a sufficiently high breakdown strength. Moreover, in the case of a high power to be transmitted, the heat developed in the converting device may be considerable even if the power loss is only 10 or 20%. To be able to discharge the power loss converted into heat, corresponding cooling means must be provided. This makes the converting device more expensive and also larger due to the additional cooling means. Components having dielectric strengths of more than 1000V, e.g. 3000 or 6000V, are, however, not available or they can hardly be realized technically. If such a converter is nevertheless suitable for such high DC voltages, the whole system will collapse if the converter fails to operate. In addition, even if the efficiency is comparatively high, the converting device will have a dissipation power that produces a substantial amount of heat comparatively locally. This amount of heat may destroy certain components of the converting device. In order to avoid such destruction, complicated cooling systems are required which entail high costs. 
     The present invention overcomes the deficiencies of the prior art. 
     BRIEF SUMMARY OF THE PREFERRED EMBODIMENTS 
     An electric control and supply system comprises a supply and control assembly at a first location and a control and actuating assembly at a remote location associated with one or more remote electrical devices. An umbilical extends between and connects the supply and control assembly with the control and actuating assembly for supplying a voltage to the control and actuating assembly. The supply and control assembly at the first location includes an AC voltage source coupled to an AC/DC voltage converter. The AC/DC voltage converter converts an AC voltage from the AC voltage source to a high DC voltage output at the first location. The AC/DC voltage converter comprises a plurality of AC/DC voltage converter components which, on the input side thereof, are connected in parallel with the AC voltage source and which, on the output side thereof, are connected serially to the umbilical. The umbilical extends to the control and actuating assembly and associated remote electrical devices at the remote location. The control and actuating assembly preferably includes a DC/DC voltage converter, although a DC/AC voltage converter may be used. The DC/DC voltage converter includes a plurality of DC/DC voltage converter components having inputs connected serially to the umbilical and having outputs providing a lower DC voltage to one or more of the remote electrical devices. The length of the umbilical typically is at least one kilometer. 
     The electric control and supply system may further include a data communication assembly for the transmission of data signals over the umbilical. The data communication assembly may include a first data coupling device coupled to the umbilical and allows communication with the remote electrical devices via the umbilical using signals associated with a first frequency range while power is supplied to the electrical devices via the umbilical. Clocking frequencies associated with one or more of the AC/DC converter components may be phase shifted with respect to each other to shift clocking noise from the first frequency range to a second frequency range. Additionally, the control and actuating assembly may further include a data communication assembly for transmission of data signals over the umbilical. The data communication assembly may include a second data coupling device coupled to the umbilical and allows communication with the control and supply assembly via the umbilical using signals associated with a first frequency range while power is supplied to the electrical devices via the umbilical. Preferably, clocking frequencies associated with one or more of the DC/DC voltage converter components may be phase shifted with respect to each other to shift clocking noise from the first frequency range to the second frequency range. Filters may be used at the first location and the remote location to remove noise conducted over the umbilical. Preferably, noise associated with, at least, the second frequency range is reduced or eliminated by the filters. 
     The electric control and supply system also includes a first controller coupled to the AC/DC voltage converter allowing control of one or more functions of the AC/DC voltage converter and a second controller coupled to the DC/DC voltage converter allowing control of one or more functions of the DC/DC voltage converter. The first data coupling device is coupled to the first controller allowing the first controller to couple data to and decouple data from the umbilical and the second data coupling device is coupled to the second controller allowing the second controller to couple data to and decouple data from umbilical. 
     The control and actuating assembly is electrically connected to the one or more electrical devices for the supply of preferably DC voltage. One type of electrical device may comprise an actuator for valves, chokes, and other closure members. The actuator comprises an electric motor being powered by second DC voltage at the remote location. A rotating spindle is coupled to the electric motor and an actuator element is adapted to be axially displaced in a feed direction by the rotating spindle rotating in a direction of advance rotation. An enclosure is disposed about the electric motor, rotating spindle, and actuator element. A first volute spring is coupled to the rotating spindle and the enclosure such that the first volute spring is operable to prevent the rotating spindle from moving in the direction opposite the direction of advance rotation. The actuator also includes an electrically activated system operable to release the first volute spring so as to allow the rotating spindle to move in the direction opposite the direction of advance rotation. The system further includes an emergency release unit operable to move the actuator element in the direction opposite the feed direction when the DC voltage is interrupted. 
     The actuator may also include a position sensor operable to determine the axial position of the actuator element. Two electric motors may be coupled to the rotating spindle for redundancy. 
     Embodiments of the invention, preferably implement a subsea umbilical having a size (cross-sectional area) and cost that is significantly reduced. In at least some embodiments, transmitting a DC voltage supply via the subsea umbilical rather than an AC voltage supply allows the size and cost of the cable in the umbilical to be reduced. Furthermore, embodiments of the invention preferably allow high voltage and high power to be supplied to a subsea electrical device while maintaining a stable power supply. 
     The electric control and supply system provides several advantages such as providing power subsea over longer distances without increasing the size of the umbilical cable, higher power transfer efficiency, redundancy, and cost benefits. 
     The system according to the invention is therefore distinguished by its simplicity and higher efficiency (at least 70%), whereby a significant cost saving can be obtained solely by the significant reduction of the cross-sectional area of the conductors in the subsea umbilical. 
     The present system does not require a separate cable to transmit data between the electric supply and control assembly and the control and actuating assembly, as does the prior art. 
     According to the invention, another advantage arises in that voltage frequencies can be modulated onto the direct voltage transmitted over the umbilical in a simple manner for data transmission. This can especially take place in that the electric supply and control assembly and the control and actuation assembly each exhibit at least one data modulation device. In at least some embodiments, the data modulation devices used in the control and actuating assembly may be disposed after the DC/DC or DC/AC converter components. 
     In summary, the system offers many advantages, such as quick response, elimination of hydraulic fluid, no dumping of fluid to sea (environmentally friendly) and the ability to perform real time diagnostics on the actuators, valves and chokes. At the surface the requirement for a hydraulic power unit is eliminated and the surface equipment is generally more compact. 
     It is therefore the object of the present invention to improve a power supply system so that it is possible to provide a high and stable voltage, even in the case of high power requirements, in a reliable manner and at a reasonable price, without any additional components for e.g. heat dissipation being necessary. The object of the present invention is to provide a power supply system to remote (e.g., subsea) electrical devices so that with small constructional efforts and with low costs, the energy supply to the remote electrical device is guaranteed over great distances. Additionally, the power supply system is stable, efficient and redundant. 
     It should also be pointed out that, due to the DC voltage transmitted to the electric devices, thin line (cross-sections) umbilical conductors are possible especially when a coaxial cable is used as the umbilical; these thin line umbilicals permit a substantial reduction of the cable connection costs. In particular, when the distances to the electric devices are in the kilometer range (e.g., 50 kilometers) and when the coaxial cable can simultaneously be used for transmitting data as well, a substantial amount of costs will be saved. 
     Expensive capacitors, such as electrolytic filter capacitors, are no longer necessary for smoothing the DC voltage on the output side. In addition, power factor correction can take place directly at the location of the control and actuating assembly. For example, a suitable means for effecting this correction can be included in the DC/DC or DC/AC converter components or rather in the integrated circuit thereof. Additionally, high frequency clocking of the DC/DC or DC/AC converter components simultaneously guarantees that the DC voltage on the input side is sampled in full width, whereby a high efficiency is obtained. 
     Other objects and advantages of the invention will appear from the following description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a detailed description of the preferred embodiments of the invention, reference will now be made to the accompanying drawings wherein: 
         FIGS. 1( a )-( b )  are schematic diagrams of various prior art control and supply systems; 
         FIG. 1( c )  is a schematic of the electric control and supply system according to embodiments of the invention; 
         FIG. 2  is a block diagram of the control and supply system according to embodiments of the invention as in  FIG. 1( c ) ; 
         FIG. 3  shows a schematic representation of an embodiment of the supply and control assembly; 
         FIG. 4  shows a schematic circuit diagram of an embodiment of a flyback converter clocked on the primary side and used as a converter component; 
         FIG. 5  is a block diagram of an embodiment of the DC voltage converting device according to embodiments of the invention; 
         FIG. 6  shows a schematic circuit diagram of a push-pull converter for use as a switched mode mains power supply in  FIG. 5 ; 
         FIG. 7  shows a circuit for a full-bridge push-pull converter; 
         FIG. 8  shows a circuit for a half-bridge push-pull converter; 
         FIG. 9  is a longitudinal section through the actuator system according to embodiments of this invention, attached to a control device such as a gate valve; 
         FIG. 10  shows a longitudinal section through the actuator system per  FIG. 9  along the intersecting line II-II in  FIG. 11 ; 
         FIG. 11  is a front view of the actuator system per  FIG. 10 ; 
         FIG. 12  is a sectional view along the line IV-IV in  FIG. 11 ; 
         FIG. 13  is a front view of an actuator system according to embodiments of this invention; 
         FIG. 14  is a cut-away view along line A-C in  FIG. 13 ; 
         FIG. 15  shows a longitudinal section through a linear control device with incorporated path-measuring device in a partial representation; 
         FIG. 16  shows an enlarged representation of a detail “X;” 
         FIG. 17  shows an enlarged representation of a detail “Y;” 
         FIG. 18  shows a circuit representation; 
         FIG. 19  shows a basic illustration of the actuating device according to embodiments of the invention with two separate electric motors and associated control device; 
         FIG. 20  shows a front view of a housing cover of the actuating device according to embodiments of the invention; 
         FIG. 21  shows a cross-section along the line IV-IV from  FIG. 20 ; 
         FIG. 22  shows a plan view onto a first embodiment of an isolating device; 
         FIG. 23  shows a section along the line II-II of  FIG. 22  with a partially represented injection valve; 
         FIG. 24  shows a section along the line III-III of  FIG. 22  or  FIG. 23 , respectively; 
         FIG. 25  shows a longitudinal section through a specific embodiment of a valve system in accordance with embodiments of the invention, having a valve and associated electrochemical actuator; 
         FIG. 26  shows a longitudinal sectional view through a rotary adjusting device in accordance with embodiments of the invention, which is removably connected to an actuator device; 
         FIG. 27  shows an enlarged illustration of the exemplary implementation of the rotary adjusting device in accordance with embodiments of the invention as shown in  FIG. 26 ; 
         FIG. 28  shows a longitudinal section of an actuating device according to embodiments of the invention comprising a throttle device from the side of a fluid inlet; 
         FIG. 29  shows a section along line III-III from  FIG. 31 ; 
         FIG. 30  is a longitudinal section through an embodiment of a pump device; 
         FIG. 31  shows a view of one embodiment of a subsea production system constructed in accordance with embodiments of the invention; 
         FIG. 32  is a schematic representation of one embodiment of the surface electrical equipment of the subsea production system of  FIG. 31 ; 
         FIG. 33  is a schematic representation of one embodiment of the subsea electrical equipment of the subsea production system of  FIG. 31 ; and 
         FIG. 34  is a schematic representation of one embodiment of the subsea flow control equipment of the subsea production system of  FIG. 31 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention relates to methods, assemblies and systems for supplying power to and controlling remote electrical devices, particularly in the oil and gas industry. The present invention is susceptible to embodiments of different forms. There are shown in the drawings, and herein will be described in detail, specific embodiments of the present invention with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that illustrated and described herein. 
     In particular, various embodiments of the present invention provide a number of different constructions and methods of operation of the electric control and supply system, each of which may be used to drill, complete, produce or workover an oil or gas well. The embodiments of the present invention also provide a plurality of methods for using the electric control and supply system of the present invention. It is to be fully recognized that the different teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce desired results. The electrically actuated actuators described herein may be substituted for any hydraulically actuated actuators used in equipment for the exploration and production of oil and gas. 
     In the description, which follows, like parts are marked throughout the specification and drawings with the same reference numerals, respectively. The drawing figures are not necessarily to scale. Certain features of the invention may be shown in exaggerated in scale or in schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness. 
     One embodiment of an electric control and supply systems  20  may be constructed in accordance with U.S. patent application Ser. No. 10/415,510, filed Apr. 29, 2003 and entitled Control and Supply System, which claims the benefit of PCT application PCT/EP01/12547 filed Oct. 30, 2001, which claims the priority of DE 200 18 560.8 filed Oct. 30, 2000 (1600-08400; OTE-030339), all of which hereby incorporated herein in their entirety. 
     Referring initially to  FIG. 1( c ) , the electric control and supply system  20  includes an electric supply and control assembly  30  at a first location  42 , an umbilical  44  extending to a second remote location  50  and connecting the electric supply and control assembly  30  with a control and actuating assembly  40  associated with a remote assembly  25  at remote location  50 . As distinguished from the prior art, the electric control and supply system  20  transmits direct voltage via umbilical  44  to control and actuating assembly  40  and not alternating voltage as in the prior art. The control and actuating device  40  is connected via connecting lines  26  to appropriate electrical devices  46  or electrical units  24  of remote assembly  25 . An electrical unit  24  may be formed by a group of electrical devices  46 , such as actuators, sensors, and control systems located at a subsea location such as hereinafter described. 
     The electric supply and control assembly  30  at the first location  42  includes at least one AC/DC converter  48 , which converts a suitable alternating voltage from an alternating voltage source  32 , into direct voltage. At the remote location  50  of the control and actuation device  40 , a DC/DC or DC/AC converter  34  is provided analogously for the conversion of the direct voltage into direct or alternating voltage as required by the electrical devices  46  or electrical units  24 . Preferably the converter  34  is a DC/DC converter to supply DC voltages to remote assembly  25 . 
     A simple voltage source for system  20 , which can also be used for other applications, can be utilized in that an alternating voltage source  32  is connected to the supply and control assembly  30  preferably for the supply of three-phase alternating voltage. 
     With the implementation of the converter  34  as a DC/DC converter, a conversion of the high direct voltage transmitted through the umbilical  44  occurs appropriately into the direct voltages required for the supply of the appropriate devices of remote assembly  25  at remote location  50 . In this connection it must be noted that with a direct voltage supply from the first location  42  to the devices  46 ,  24  of remote assembly  25  at remote location  50 , a suitable data interchange with these devices is simplified, because appropriate data signals can be modulated onto the direct voltage signal in a simple manner. 
     Due to the DC/DC or DC/AC converter  34  in the remote area  50  of the control and actuating device  40 , a corresponding conversion of the direct voltage takes place into the required direct or alternating voltage values, such as for example, 240V or 300V with the appropriate frequency, for the electrical devices  46  such as motors, actuators and similar equipment of assembly  25 . 
     The electric control and supply system  20  is able to transmit direct voltage via the long subsea umbilical  44 , whereby the conversion from alternating voltage into direct voltage or vice versa from direct voltage into alternating voltage only takes place at the ends of the umbilical  44 . With direct voltage and the corresponding direct current, only real power is transmitted via the umbilical  44  and no apparent power. This means that the power factor is 1. Due to the direct voltage transmission along the umbilical  44 , even with high voltages, only slight losses are present in comparison to a transmission of alternating voltage with previously known prior art systems. 
     Furthermore, with the transmission of direct voltage, only small cross-sectional areas arise for a conductor in the umbilical  44  which may be only one tenth or less of the cross-sectional areas for the transmission of alternating voltage. 
     Since, according to the invention, a direct voltage is transmitted through the umbilical  44 , correspondingly no transmission of high frequency voltages occurs, so that signals for data transmission can be modulated onto the direct voltage in a simple manner. The data transmission may take place through the multiplexer device  52  and through an appropriate cable coupler  54 . The multiplexer device  52  may couple different data channels to the cable coupler  54 . For example, each data channel may be associated with a different user-interfaced computer. Therefore, users of different computers are able transmit commands, data, etc., to the control and actuation assembly  40  via the multiplexer device  52 . Demodulation of the data occurs appropriately at the remote area  50  of the control and actuation assembly  40 . 
     The electric control and supply system  20  may be used, for example, in the drilling, completion, production and workover of oil and gas and may be used with land based wells or offshore wells. The electric control and supply system is particularly advantageous when a wellhead assembly is remote from the electric supply  32 , such as for example when the wellhead assembly is many kilometers from the supply  32 . The electric control and supply system  20  is still more particularly advantageous for use on an offshore well because of the more harsh environment caused by working subsea. Although the following embodiment is described with respect to an offshore well, by way of example, it should be appreciated that the electric control and supply system  20  of the present invention may also be used in a land based well. 
     Referring now to  FIG. 2 , there is shown another embodiment of an electric control and supply system  60  according to the invention for an offshore well. The electric control and supply system  60  includes an electric supply and control assembly  70  arranged on a platform or vessel  62  above the sea surface  64  and a control and actuation assembly  80  below the sea surface  64 , such as at the sea floor  66 . These are connected by a subsea umbilical  68 . The electric supply and control assembly  70  is connected to an alternating voltage source  78  which preferably provides a three-phase alternating voltage. 
     The electric supply and control assembly  70  comprises at least one AC/DC converter  72  and a data modulation device  74 . A surface control device  76  controls both the AC/DC converter  72  and the data modulation device  74 . Furthermore, the electric supply and control assembly  70  is connected to a data transmission device  82  which can be positioned remotely from the electric supply and control assembly  70 , but which is still part of the control and supply system  70 . The control of the complete system  60  and its monitoring can occur through the data transmission device  82 . 
     The arrows shown between the various units in system  60  indicate by the arrow direction, a transmission of voltage or data, whereby generally a bidirectional data transmission is possible. 
     The control and actuation assembly  80  is positioned below the sea surface  64  and, for example, on the sea floor  66 . It comprises a data modulation device  84  for demodulation of the data transmitted through the subsea umbilical  68 , but also for the modulation of appropriate data onto the voltage transmitted through the subsea umbilical  68  when such data is transmitted in the reverse direction from the control and actuation assembly  80  to the supply and control assembly  70 . 
     Following the data modulation device  84 , the control and actuation assembly  80  comprises a voltage converter  86 . For example, the voltage converter  86  may comprise a DC/DC voltage converter or a DC/AC voltage converter. Using the voltage converter  86 , the direct voltage transmitted through the subsea umbilical  68  is converted into a suitable direct or alternating voltage. In order to prevent the occurrence of high currents and, where applicable, of damage to the relevant electrical devices, especially on the sea floor, an over current control device  88  can be assigned to the voltage converter  86 . 
     Following conversion of the direct voltage into a suitable voltage, an inductive transmission of the suitable voltage occurs to a voltage measurement device  90 . The inductive transmission occurs through a transformer  92  consisting of two coil cores  94 ,  96 . In at least some embodiments, the coil cores  94 ,  96  may be half-coil cores. An air gap  98  is formed between the coil cores  94 ,  96 . 
     The coupling control devices  108 ,  110  are used for the interchange of data. For example, the coupling control device  110  may permit the voltage measurement device  90  to communicate with a subsea electronic module  112 . The electronic module  112  may contain electronics for controlling the various items of equipment below sea level and in particular on the sea floor, such as valves, blow-out preventers, actuators and similar equipment. Generally, the appropriate electronics is contained redundantly in the electronic module. 
     The voltage measurement device  90  may measure the amplitude of the suitable voltage. In some embodiments, the voltage measurement device  90  may implement a voltage shunt regulator  100 . The voltage shunt regulator  100  provides an appropriate static and/or dynamic stabilization of the suitable voltage. In order to pass data in the direction of the supply and control assembly  70  directly from the electrical devices  46 ,  24 , the voltage measurement devices  90  and the voltage shunt regulator  100  may be bi-directional. 
     Due to the voltage shunt regulator  100 , the system  80  can, for example, run under full voltage before the actuation of the electrical devices  46 ,  24 , whereby the voltage shunt regulator  100  takes over the dynamic load regulation and then can reduce the voltage to appropriately low values. The stabilized suitable voltage may then be passed to a subsea voltage source  102  to which the various electrical devices  46  or units  24  are connected via electrical connecting lines  26 . 
     By using the usual electrical connectors, it is also possible for all the connected parts to be recovered and to be retrieved from below sea level and, for example, to service them and reuse them later. According to embodiments of the invention, a non-fixed (i.e., releasable) connections between, for example, the subsea umbilical and subsea devices may be implemented. 
     The control and actuation assembly  80  operates utilizing direct voltage transmitted through subsea umbilical  68 . The direct voltage is converted to either a lower DC voltage or to alternating voltage by an appropriate converter  86  at the subsea floor  66  only after the DC voltage has been transmitted through the long subsea umbilical  68 . Above the surface  64  of the sea, a three-phase alternating voltage is converted by an AC/DC converter  72  to, for example, an output voltage in the range of from 3000 to 6000V. The voltage value depends on the power requirements of the system  60 . 
     Then, the direct voltage is transmitted through coaxial conductors in the subsea umbilical  68 . Additionally, data signals may be modulated onto the direct voltage via a suitable data modulation device  74 , such as a modem or similar device. Since coaxial conductors exhibit optimum properties with regard to attenuation and electrical noise, high data transmission rates of at least 100 to 600 kBaud are possible. However, embodiments of the inventions are not limited to coaxial conductors and other existing or future conductors may be implemented. 
     At the sea floor  66  or below the surface  64  of the sea, a demodulation of the data signals occurs using a suitable data modulation device  84 , again such as a modem. Then, conversion of the direct voltage occurs by converter  86  into, for example, a rectangular wave voltage of 300V with a frequency of 20 kHz. This voltage is transmitted to the various electrical devices  46 ,  24 . Only slight filtering is required such that large electrolytic capacitors are not necessary. The transformer  92  converts the voltage of the converter  86  to the appropriate voltage values utilizing the two coil cores  104 ,  106 , separated by the air gap  98 . The coil cores  104 ,  106  are assigned to one another, separable from one another and may be formed mutually symmetrically. The transformer  92  provides the inductive coupling. 
     The transformer  92  can be realized such that the air gap  98  between the two cores  94 ,  96  is, for example, in the millimeter range (e.g., 1 to 5 millimeters). In addition, appropriate materials for the coil cores  94 ,  96  can be used which are not susceptible to attack by sea water  114 , such as arrangements of corrosion-resistant transformer steel sheet or plastic encapsulated magnetic powder mixtures for the appropriate coil core materials. 
     In order to couple data to or from the control and actuation assembly  80 , the data modulation device  84  of the control and actuation assembly  80  may be positioned before the voltage converter  86 . Therefore, the data may be coupled to or from a direct voltage. In at least some embodiments, data may be transmitted from the measurement device  90  via the data modulation devices  106  and  104  and further via the further data modulation device  84  to the voltage supply and control device  70  for regulation of the voltage supply. 
     Using appropriate calculations for the required voltage values and powers, a conductor cross-sectional area of only approximately 2 mm 2  arises for, for example, a length of 50 km of subsea umbilical with the voltage control and supply system  60  according to the invention. This is a substantially lower cross-sectional area than with prior art systems. 
     In addition, high data transmission rates are possible due to the simple modulation and demodulation with respect to the direct voltage and the coaxial cable used. Through the devices used in the system  60  according to the invention, a stable supply voltage and high system reliability arise. With a simple embodiment without further control devices, the voltage measurement device  90  can be connected to the electrical devices  46 ,  24  for their supply. 
     A separate voltage stabilization, for example, using a Zener diode  240  arrangement is no longer necessary due to the voltage measurement device  90  with voltage shunt regulator  100  according to the invention, because the voltage provided is already statically and dynamically stabilized. 
     For the transmission of the direct voltage and also the electrical signals along the subsea umbilical  68 , the umbilical can be advantageously formed from coaxial conductors. These exhibit optimum properties with regard to attenuation and immunity with regard to radiated noise and they enable a high data transmission rate of at least 100 to 600 k Baud. Furthermore, bidirectional transmission of data along the subsea umbilical  68  can also be carried out simply. 
     Due to the application according to the invention of direct voltage or direct current and the resulting possible small cross-sectional areas of the conductors in the subsea umbilical  68 , there is also the possibility that for each electrical device  46 ,  24  a separate connecting conductor can be provided in the subsea umbilical  68 . In this relationship it must be noted that an electrical unit  24 , for example, a single motor or a single actuator can also be a suitable tree structure or group of electrical motors, actuators or other electrical devices. 
     A suitably simple coupling of data—also multi-channel—can be realized in that the system  60  exhibits a multiplexer device  52  with the data transmission device  82 . The multiplexer device  52  may couple different data channels to the controller  76 . For example, each data channel may be associated with a different user-interfaced computer. Therefore, users of different computers are able transmit commands, data, etc., to the control and actuation assembly  80  via the multiplexer device  52 . 
       FIG. 3  shows a schematic circuit diagram of the electric supply and control assembly  70  disclosed in U.S. patent application Ser. No. 10/489,573 filed Mar. 12, 2004 and entitled Universal Power Supply System, which claims the benefit of PCT/EP02/10471 filed Sep. 18, 2002, which claims the priority of DE 201 15 471.9 filed Sep. 19, 2001 (1600-09300; OTE-030452); and U.S. patent application Ser. No. 10/489,583 filed Mar. 12, 2004 and entitled Universal Power Supply System, which claims the benefit of PCT/EP02/10468 filed Sep. 18, 2002, which claims the priority of DE 201 15 473.0 filed Sep. 19, 2001 (1600-09500; OTE-030454); all of which are hereby incorporated herein by reference in their entirety. Electric supply and control assembly  70  receives AC power from AC power source  78  (see  FIG. 2 ). The AC power may comprise an alternating 380 V three-phase power source. As shown, the electric supply and control assembly  70  may comprise an AC/DC converter  72  having a plurality of AC/DC converter components  122  which are connected in parallel to the line  120  via respective input terminals  124 . 
     Due to this mode of connection of the AC/DC converter components  122 , each of these components  122  only serves to generate a certain percentage of the voltage on the output side of the AC/DC converter  72 . If the DC voltage which is to be produced on the output side  75  amounts e.g. to 6000V, the DC voltage can be produced by, e.g., 20 converter components  122  each having an output voltage of 300V. It is also possible to provide 30, 40 or 50 converter components  122 , each of these converter components  122  providing a respective percentage of the DC voltage required on the output side  75 . 
     In the simplest case, the converter components  122  all have the same type of structural design so that, in the case of n converter components  122 , each converter component  122  produces the nth percentage of the necessary output voltage from the AC voltage applied to the input side. 
     Due to the use of a plurality or multitude of AC/DC converting units  122 , each individual converting unit  122  is only responsible for providing a specific amount of the voltage needed on the output side. If all of the converting units  122  are of a similar construction, each individual converting unit provides, for instance, only the nth part of the necessary output voltage. 
     The AC/DC converter components  122  may comprise switched mode power supplies  126  and, in particular, flyback converters  130  clocked on the primary side and acting as a switched mode power supply  126 . 
     On the output side  75 , the various converter components  122  are serially connected to one another via respective output terminals  132  and they are connected to umbilical  68  and connections  134 . Via the connections  134 , the control and actuation assembly  80  at a remote location has electric power supplied thereto. Between the AC/DC converter  72  of the supply and control assembly  70  and the control and actuation assembly  80 , a means for coupling data signals in/out  136  is additionally connected to the umbilical  68  and connections  134 . The means for coupling data signals in/out  136  is used for transmitting respective data signals or for coupling out data signals that have been received from the control and actuation assembly  80  or from units associated therewith. The transmission of the data signals is also effected via the connections  134  and umbilical  68 . 
     In  FIG. 3 , only one control and actuation assembly  80  is shown. Normally, a plurality of control and actuation assemblies  80  have supplied thereto electric power and also data via the connections  134  and umbilical  68  from the supply and control assembly  70  according to the present invention. Such control and actuating assemblies  80  include electric devices  46  such as actuators located at sites, which are remote and/or not easily accessible. The actuators control e.g. units of fluid lines, such as valves, shut-off devices, restrictors, pumps and the like, so that the flow of fluid into and along the fluid line is controlled and shut off in emergency cases, such as leakage, line fractures or the like, and so that also parameters of the fluid, of the fluid flow or of the respective units are monitored and controlled. The fluid is normally fed into the lines under high pressure from a respective fluid source and conducted along such lines e.g. from the bottom to the surface of the sea. Since such a fluid normally contains aggressive or environmentally noxious components, a power supply and remote control which can be effected with the aid of the power supply system according to the present invention is of great advantage. 
     The remote control of the respective actuators can in this connection be carried out via the communication connection established with the aid of the means for coupling data signals in/out  136 . 
     All the units of the supply and control assembly  70 , including, if desired, the control and actuation assembly  80 , are adapted to be controlled and/or regulated by controller  76 . In addition, a relevant monitoring of parameters of the various units can be carried out. In  FIG. 3 , the controller  76  is connected to the various units via connections represented by broken lines, so as to control, regulate and/or monitor said units. 
     The switched mode power supplies  126  and flyback converters  130 , respectively, can be implemented as integrated circuits. These integrated circuits directly comprise respective further units, such as power factor control means  140 , under voltage detection means  142  or over voltage monitoring means  144 . In order to simplify the illustration, these additional units are shown in  FIG. 3  only in the case of one AC/DC converting component  122 ; normally, they are, however, component parts of all of the AC/DC converting components  122 . 
       FIG. 4  shows a simplified embodiment for a flyback converter  130  acting as a switched mode power supply  126 . The flyback converter  130  comprises a transformer  92  having a primary winding  104  connected to the input terminal  124  and a secondary winding  106  connected to the output terminal  132 . An effective magnetic coupling exists between these two windings,  104 ,  106 . The transformer  92  acts as a magnetic energy storage. When a switching means  150  in the form of a power transistor  152  is closed, the current will increase in the primary winding  104  and energy will be stored in the transformer  92 . When the switching means  150  is opened, the stored energy on the side of the secondary winding  106  will be supplied to a smoothing capacitor  154  via a diode  156 . The stored energy is thereby output via the output terminal  132 . In at least some embodiments, the switching means  150  is designed as a power MOSFET  152 . Furthermore, it is possible to design the switching means  150  as a BIMOSFET or as a power thyristor. 
     The respective flyback converters  130  have their output terminals  132  serially connected to the connection  134 , cf.  FIG. 1 . 
     For activating or clocking the switching means  150 , i.e. the power transistor  152 , a pulse width modulation means  160  is provided in the flyback converter  130 . The pulse width modulation means  160  produces a pulse width-modulated signal whose clock cycle ratio is controlled in accordance with the measured actual value of the output voltage. For this purpose, the actual value measured at the output of the flyback converter  130  is subtracted from the respective desired value and this difference is supplied, via a control amplifier of the flyback converter  130 , to the pulse width modulation means  160 . Here, the output voltage of the control amplifier of the flyback converter  130  is compared with a sawtooth voltage whose frequency determines the clock frequency of the flyback converter  130 . Depending on the result of this comparison, the switching means  150  is switched on or off and the desired output voltage is adjusted in this way. The maximum output voltage is normally defined by the breakdown voltage of the switching means  150  and the corresponding power MOSFET  152 , respectively. 
     A pulse width modulation means  160 , in particular a pulse width modulation means  160  which is adapted to be controlled or regulated, can be provided for activating the switching means  150  of the flyback converter  130  or of the switched mode mains power supply  126  in a suitable manner. 
     This pulse width modulation means  160  is capable of producing a series of pulses, which are adapted to be varied with respect to their width and/or height and/or frequency. A frequently used pulse modulation means is a pulse width modulation means  160 . This pulse width modulation means  160  produces a pulse width-modulated signal whose clock cycle ratio can be controlled in accordance with a measured actual value of the output voltage. The measured actual value of the output voltage can, e.g. be subtracted from the desired value and this difference can be supplied via a control amplifier of the flyback converter  130  to the pulse width modulation means  160 . 
     Here, the output voltage of the control amplifier of the flyback converter  130  can be compared with a sawtooth voltage whose frequency determines the switching frequency or clocking of the switched mode mains power supply  126 . Depending on the result of this comparison, the switching transistor  150  is then switched on or off, whereby a desired output voltage can be adjusted. 
     The clock frequency of the switching means  150  can be in the kilohertz range and in particular in the hundred-kilohertz range so as to permit a sufficiently fast clocking of the switching means  150  and, in this connection, a comparatively low dissipation power of the flyback converter  130 . For example, flyback converters  130  are known, which are clocked in the range of from 20 kHz to 200 kHz. Lower and higher clock frequencies are, however, possible as well. 
     In order to avoid, especially in the case of high power values, the necessity of providing separate cooling means for the converter components  122 , such converter components  122  can be arranged in spaced relationship with one another. The spatial distance is, however, so small that, normally, it corresponds only to the dimensions of one converter component. 
     In connection with the converter components  122  and especially the flyback converters  130  used as such components, attention should also be paid to the fact that each of each of such converter components  122  should be adapted to be controlled or regulated separately with respect to its output voltage. The inputs of the converter components  122  are arranged in parallel in each converter component so that the voltage supply and, consequently, current and power are fully separated. It follows that, irrespectively of the output voltage, also the total power of the system can be adapted according to requirements. A completely free selection of the power and of the output voltage is therefore possible. Due to the use of a plurality of converter components  122 , an extremely exact and precise control of the output voltage as well as of the power are additionally obtained, since each converter component controls independently of the other components only its own range. 
     If one of the converter components  122  fails to operate, the power supply is still guaranteed (redundancy), since the other converter components  122  are activated in a suitable manner so that the power failure of the converter component that failed to operate will be compensated for on the output side. The respective range within which each of the still operative converter components  122  has to be adjusted is extremely small, since a comparatively low increase in the voltage on the output side of the plurality of converter components  122  will already lead to a substantially higher increase in the total output voltage. 
     In connection with each converter component and especially in connection with the flyback converter  130 , it is possible to dispense with additional components, i.e. to implement such converter components  122  e.g. as integrated circuits comprising in addition to the actual flyback converter  130  other elements, such as a power factor control means, an under voltage detection means, an over voltage monitoring means, a so-called “soft start” and the like. 
     At least the AC source and/or the AC/DC converter and/or the means for coupling data signals in/out  136  may have associated therewith the controller  76  so that the various units of the power supply system according to the present invention can be monitored, controlled or, if necessary, regulated more effectively. This controller  76  can e.g. also detect whether one of the converter components  122  implemented as a flyback converter  130  has failed. If such failure is detected, the other flyback converters  130  can be activated such that they compensate for the failure of such one flyback converter  130  in that a slightly higher output voltage is e.g. delivered by each of the other flyback converters  130 . 
     The controller  76  can also control the pulse width modulation means in this connection. 
     The controller  76  can not only be used for monitoring purposes alone, but it is also possible to use it for establishing a communication connection between the respective units of the power supply system. This will be of advantage especially in cases in which the various units are arranged at comparatively large distances from one another and/or at inaccessible sites. With the aid of this communication connection, physical examination or maintenance can be limited to rare cases or to cases where the unit in question has to be replaced. 
     To monitor, control and optionally regulate all devices of the energy supply system  60  and possibly also the electrical devices via the umbilical connection  68 , a controller  76  may be assigned at least to the AC voltage source and/or the AC/DC converting means and/or the data signal coupling/decoupling means and optionally also to the electrical device. Such a controller  76  yields an intelligent supply system, which controls and/or regulates a great number of parameters. An example of the activity of the controller  76  may be seen in the measure that said controller  76  controls the flyback converters  130  not only with respect to their output voltage, but also monitors them with respect to their function. For instance in case of failure of one flyback converter  130 , a message may be sent by the controller  76  to a corresponding monitoring means that one and possibly also which one of the flyback converters  130  has failed or is impaired in its function. At the same time, the controller  76  can control the remaining flyback converters  130  such that they compensate for the voltage failure. A corresponding message may also be sent. After failure of a number of flyback converters  130 , the system according to the invention may also send a corresponding repair request through the controller  76 , whereby full operability of the energy supply system would be guaranteed up to the time of the repair. 
     The controller  76  may also detect further possible defects in the energy supply system and optionally also in the electrical devices supplied by the system. For instance, electrical devices may optionally be switched on and off via the data signal connection, controlled in their operation or influenced in another way. 
     To permit a direct querying of different means and also of the electrical device via the controller  76  at the same time, a communication connection with the respective means of the energy supply system and optionally with the electrical device may be established via the controller  76 . 
     In contrast to an AC/DC converter for producing e.g. 6000V, such converter components  122  are easy to handle and easy to maintain. The dissipation heat per converter component is here normally so low that separate cooling means can be dispensed with. If the converter components  122  are arranged comparatively close to one another, simple cooling means conducting, e.g., cooling air over the converter components  122  will suffice even in the case of high power. In comparison with known converters, the costs for cooling the AC/DC converter  72  are reduced substantially. 
     If one of the converter components  122  fails to operate, the output voltage will only be reduced by such nth part so that also the remaining n−1 converter components  122  will still provide a sufficiently high voltage for the electric device. Only if a plurality of converter components  122  fails to operate, may it prove to be necessary to replace such converter components  122 , at least partially. In any case, if one of the plurality of converter components  122  fails to operate, it is still guaranteed that the voltage supplied to the electric device will still be sufficiently high to permit operation thereof (providing redundancy). 
     A filter means  170  can be arranged between the AC/DC converter and the electric device so that, if necessary, the DC voltage generated by the AC/DC converter can be smoothed still further. 
     In the case of certain electric devices, it may prove to be advantageous when also a signal connection is provided in addition to a voltage supply. In order to avoid the necessity of providing an additional cable connection to the electric device for this purpose, a means for coupling data signals in/out  136  can be connected to the umbilical connection, such means for coupling data signals in/out  136  being especially located between the filter means  170  and the electric device. This means for coupling data signals in/out  136  can, on the one hand, be used for coupling respective data signals into the data connection for, e.g., controlling the electric device or for supplying information thereto. In the opposite direction, data received from the electric device can be coupled out from the umbilical connection and used, e.g., for monitoring the electric device by means of suitable units, such as computers and the like. 
     In this connection, it must betaken into account that data transmission on the basis of the output-side DC voltage can be effected with less interference and with a higher velocity than in cases in which the electric device is supplied with an AC voltage. 
     Interference frequencies on the umbilical connection are also approximately within the range of the clock frequency, which results in already relatively high interference frequencies when 100 kHz are used. Such high interference frequencies do normally not affect the components of the energy supply system or the electrical device. 
     If the interference frequencies are to be shifted into an even higher frequency range, at least some of the clocked switch mode power supplies may be phase-shifted relative to one another in their clock frequencies. It is true that a natural frequency is maintained for each of the individual flyback converters  130 , i.e., e.g. a clock frequency of 100 kHz. With this frequency direct current is fed accordingly on the secondary side into the cable. If said clocked feed is shifted by the phase shift of the clocking of individual converting units (e.g., by only one nano second fraction each at the time of feed) one will obtain a cutoff frequency of the system (i.e., the cutoff frequency of the interference on the secondary side) of 100 kHz×n, n being the number of the flyback converters  130  that are phase-shifted with respect to their clock frequency. For instance, if n equals 30, a system cutoff frequency of 3 MHz is obtained. At the same time, the magnitude of the interference voltage output is reduced to 1/n of the interference voltage of an individual unit. 
     Such a shift in the cutoff frequency of the system is in particular of considerable advantage when a data transmission takes place via the cable connection simultaneously with the energy supply. To this end a data signal coupling/decoupling means may be provided according to the invention. Such means serves both to feed data which are e.g. to be transmitted from the electrical devices, and to decouple data received by the electrical devices or other units of the energy supply system. 
     Since a corresponding data signal transmission normally takes place within the range of a few 10 kHz, possible residual interferences by the system cutoff frequency are far away from any data transmission bandwidth. Troublesome filtering, e.g. by filter electrolyte capacitors, are not needed for smoothing the output voltage, and a safe data transmission that is as fast as possible is obtained on an almost undisturbed umbilical connection. 
     To make data transmission even safer, a simple filter means  170  may be arranged between AC/DC converting unit and electrical device. However, this means is only used according to the invention for filtering remaining interference within the data transmission, i.e. up to a few 10 kHz, e.g. 50 kHz. 
     Subsequent to the AC/DC converter  72 , a filter means  170  is disposed in the umbilical  68 . The filter means  170  filters interference above the frequency range of a few tens of kilohertz, which interference might disturb a data transmission via the umbilical  68 . 
     The data signal coupling/decoupling means  136  is arranged between the filter means  170  and the at least one control and actuation assembly  80  supplied by the supply and control assembly  70  with DC voltage and high power. Corresponding data signals are coupled via such means  136  into the umbilical  68 , or data signals transmitted from the control and actuation assembly  80  via the umbilical  68  are decoupled by such means  136 . An interference-free data transmission at a high speed (tens of kilohertz) is thereby made possible via the umbilical  68 . It should here be noted that the cutoff frequency of the system  20  may be shifted by a shift of the clocking frequencies of the individual converter components  122  into the range of MHz, so that said cutoff frequency is far away from any data transmission bandwidth and a reliable data transmission at a high speed is thereby possible. 
     The control and actuation assembly  80  may e.g. include an actuator, and it is self-evident that several control and actuating assemblies  80  can be supplied accordingly via the umbilical  68  with both power and data. Such an actuator serves e.g. to control means along a fluid line. The corresponding means and actuators, respectively, for the actuation thereof are normally arranged at remote places, which are difficult to reach, or are impassable and confined. The fluid can flow at a high pressure into or through the fluid line, so that e.g. one means is an emergency shut-off unit, which in case of leakage in the fluid line prevents possibly aggressive or environmentally harmful fluid from exiting into the environment. Further means for actuation by the actuators are valves, throttles, pumps, or the like. As a rule, the actuators require much power because the fluid flows at a high pressure and possibly also with a large quantity through the fluid line or into the same. It is also possible to provide a corresponding shut-off device already during inflow, i.e. substantially at the source of the fluid, to prevent an uncontrolled outflow of the fluid into the environment. 
     Of course, it is here of advantage when corresponding parameters of the actuators and of the means controlled by them, e.g. positions of the valve, shut-off device, action of the pumps, or the like, can be queried and monitored through the communication connection. 
     The control of the communication connection and the monitoring of all means take place via the controller  76  which is connected to all of the corresponding means and also to the control and actuation assembly  80 . 
     Using the controller  76 , it is possible to precisely regulate the power for control and actuation assembly  80  with the associated voltage and to carry out the regulating operation with a multitude of flyback converters  130 . Moreover, the controller  76  may control the phase shift in the clocking of each flyback converter  130  to yield a very high cutoff frequency of the system  20 , which permits an interference-free data transmission via the corresponding connection  134  also over long umbilical distances and even in the case of a thin cross-section of the umbilical at a high speed. 
     In case of failure of one or several flyback converters  130 , the controller  76  may operate to adjust the output voltage provided by the remaining flyback converters  130  so that an adequate voltage and power supply on the output side of the AC/DC converter  72  is still provided for the corresponding control and actuation assembly  80 . 
     In accordance with an advantageous embodiment, the maximum output voltage of each switched mode mains power supply is chosen such that it does not exceed a limit value below the breakdown voltage of a respective component of the switched mode mains power supply, especially of the switching means  150 , so that a safety distance from the breakdown voltage is kept. 
     As has already been mentioned hereinbefore, the flyback converters  130  are clocked on the primary side. In this connection, it may of advantage when the flyback converter  130  provides a plurality of galvanically separated, controlled output voltages. 
     Such an adjustment of the output voltage is of advantage, in particular, in case of failure of one or several converting units. For instance, if among the above-indicated number of 30 converting units one fails, the output voltage is only reduced by 200 V. 
     The system as such remains operative and can supply the electrical device with enough power. Moreover, due to the adjustability of the output voltage of each converting unit, it is still possible to readjust the missing 200V, advantageously, via all of the remaining converting units. Since each of the remaining converting units must only produce a minimum amount of the missing 200V, the output voltage is each time increased by a small amount only. The converting units may here be designed such that, for instance during normal operation while all of the converting units are working, the units only output—as the output voltage—a fraction of the maximum output voltage that can be produced by them. As a result, the readjustment range is relatively large, so that several converting units may also fail without collapse of the system. 
     Referring now to  FIG. 5 , the converting device  86  of control and actuation assembly  80  (see  FIG. 2 ) preferably is a DC converting device having a plurality of DC converting units  180  in the form of switch mode power supplies  182 . Converting device  86  may be constructed in accordance with U.S. patent application Ser. No. 10/489,453 filed Mar. 12, 2004 and entitled DC Voltage Converting Device, which claims the benefit of PCT/EP01/12547 filed Oct. 30, 2001, which claims the priority of DE 200 18 560.8 filed Oct. 30, 2000 (1600-09400; OTE-030453), which are all hereby incorporated herein by reference in their entirety. The switch mode power supplies  182  are wired one after the other on the input side and connected to the output side of the supply and control assembly  70  via connection  184  with umbilical  68 . The supply and control assembly  70 , providing DC voltage, is located at a remote place from the control and actuation assembly  80 ; the length of the umbilical  68  may here be several kilometers, for instance 50, 60 or more kilometers. 
     A filter means  190  is disposed upstream of the DC voltage converting units  180 . Filter means  190  filters, in particular, a frequency range needed for a communication connection to the DC voltage source of the supply and control assembly  70 . The filtering operation may e.g. be carried out within a frequency range of up to 50 kHz. 
     The DC voltage converting units  180  and the corresponding switch mode power supplies  182 , respectively, are wired in parallel with one another on their output side and connected accordingly with a connection  186 . The connection  186  leads to at least one electrical device  46  such as an actuator. 
     The actuator  46  may function with a means for controlling a fluid flow into a fluid line or within the fluid line. Such means may comprise, e.g., valves, shut-off devices for emergency cases, such as leakage, pipe breakage, or the like, throttles, pumps, etc. These means and the actuators  46  assigned to them are possibly disposed in rough terrain that is difficult to reach. The means and actuators  46  may also be arranged underwater. The fluid can enter into the ducts at a high pressure and be guided there along. Moreover, the fluid may be aggressive or pollute the environment, so that a corresponding monitoring and control of the fluid flow is of utmost importance. 
     The actuators  46 , as well as the DC converting device  86 , may be arranged below sea level. The umbilical connection  184  can extend up to the water surface to the supply and control assembly  70 . It is also possible that the actuators  46  are arranged on the surface of the earth at a place that is difficult to reach, and are controlled and monitored accordingly from a remote place. 
     The coupling control devices  108 ,  110  shown in  FIG. 2  are used for the interchange of data. As shown in  FIG. 2 , subsea electronic module or controller  112  may contain electronics for controlling the various items of equipment below sea level and in particular on the sea floor, such as valves, blow-out preventers, actuators and similar equipment. Generally, the appropriate electronics is contained redundantly in the controller  112 . The controller  112  may be assigned at least to the DC voltage converting device  86  for monitoring, controlling and regulating the corresponding DC converting units  180 . This controller can also monitor, control or regulate other components of the control and actuation assembly  80 . 
     For the transmission of corresponding data to the supply and control assembly  70  and means further assigned to such source, a data coupling/decoupling means  84  may be provided. This means is arranged upstream the filter means  190  between filter means  190  and the supply and control assembly  70 . Corresponding data signals can be coupled and decoupled, for instance, by the controller  110  into and out of the connection  184  via the data coupling/decoupling means  84 . A communication connection is thereby established between the supply and control assembly  70  and the control and actuation assembly  80 . The communication connection is bidirectional, so that data can be exchanged in both directions via the connection  184 . 
     Due to the use of the plurality of converting units  180  and the configuration of the units  180 , each unit  180  converts only part of the high DC voltage supplied by the supply and control assembly  70 . For instance, if a DC voltage of 6000V is provided from the supply and control assembly  70  as an input to the control and actuation assembly  80 , each of the converting units  180  will only convert the nth fraction of the input voltage if these are of an identical construction and on condition that there is a number of n converting units  180 . For instance, if n is 30, each converting unit  180  would only convert 200V. The breakdown strength of the corresponding components of the converting units is normally considerably higher than 200V, so that there is no risk in this respect. 
     On the output side, depending on the design of the converting units  180  and with a corresponding wiring to the cable connection  186 , it is e.g. possible to provide a DC voltage value of 300V for the actuator device  46 . 
     Of course, it is possible to use different numbers of converting units  180 . It is also possible that the converting units  180  are of no similar construction, but convert, e.g., different amounts of the input voltage per converting unit into a corresponding output voltage. However, for reasons of maintenance and repair, it is of greater advantage to give all converting units  180  an identical design. 
     Moreover, it is ensured through the number of the converting units  180  that, when one, two, three or even more converting units  180  fail, a complete failure of the voltage supply to the electrical device need not be feared, because the converting units  180  that are still operative can be clocked to receive more voltage on the input side and convert the input voltage into the output voltage required. 
     It is therefore the object of the present invention to provide a DC converter  86  that is structurally simple and is able to reliably convert high DC voltages even in the case of high power, in such a way that the reliability of the converter  86  is increased and cooling systems entailing high costs can be dispensed with. 
     As shown in  FIG. 5 , the DC converter  86  may comprise a plurality of DC converter components  180 , each of said DC converter components  180  being, on the input side, serially connected to the control and supply assembly  70  and, on the output side, connected in parallel to the cable connection  186  so as to provide the converted DC voltage for the electric device  46 . 
     In at least some embodiments, the converting units  180  may be spaced apart from one another such that they do not mutually affect one another in their heat development, and each converting unit  180  can thus be cooled separately. 
     Depending on the number and design of the converting units, DC voltages of about 1 kV to 10 kV and, in particular, 3 kV to 8 kV may be present on the input side. It should once again be pointed out that even higher input voltages with a correspondingly high power can be converted if the number of the converting units  180  or their corresponding construction is matched accordingly. Care should be taken such that the breakdown strength of the components of every converting unit  180  is at least so high that the amount of the input voltage to be converted by the converting unit  180  is smaller than the breakdown strength. 
     To implement highly efficient converting units  180  that, consequently, only generate a small amount of heat and thus ensure a high reliability and, economically speaking, are excellent in production and operation at the same time, a corresponding DC voltage converting unit  180  may be designed as a clocked switch mode power supply  182 . In comparison with, e.g., linear controlled power supplies, a clocked switch mode power supply  182  offers advantage such as smaller size, less noise development, reduced smoothing demands and an increased input voltage range. 
     Various realizations of such a clocked switched mode power supply  182  are known. The first subdivision that can be carried out is a division into switched mode mains power supplies  182  clocked on the secondary side and those clocked on the primary side. In both said fundamental versions, it is possible that a current flows constantly into a storage capacitor of the switched mode mains power supply  182  or that a current is only discharged at certain time instances so that the converter in question is referred to as a feed forward converter or a flyback converter  130 . In order to obtain a compact and reliable component, the switched mode mains power supply  182  can, for example, be implemented as a flyback converter  130 . This flyback converter  130  can preferably be clocked on the primary side so as to obtain a galvanic separation between the input and output sides, and it can be a single-phase or a push-pull converter. Single-phase converters are, in this context, advantageous insofar as they normally require only one power switch as a clock switching means  150 . 
     This power switch  150  can be implemented e.g. as a power MOSFET or as a BIMOSFET. In addition, also thyristors may be used as clocked switching means  150  especially when high power values in the kilowatt range are involved. 
     The above-mentioned switched mode mains power supplies  182  have, especially in the case of higher power values, a plurality of advantages, such as a lower dissipation power, a lower weight, a smaller volume, no generation of noise, less smoothing outlay and a larger input voltage range. Switched mode mains power supplies  182  and especially also flyback converters  130  are used in a great variety of fields of application, such as microwave ovens, computers, electronic adapting equipment for fluorescent lamps, industrial and entertainment electronics, screens, cardiac defibrillators and the like. Flyback converters  130  are also excellently suitable for use in fields of application where a high power is required on the output side. 
     The switch mode power supplies  182  can be subdivided into primarily and secondary clocked switch mode power supplies. The secondary clocked switch mode power supplies include, for instance, step-down and step-up converters. However, in order to realize an electrical isolation between input and output, primarily clocked switch mode power supplies and, in particular, flyback converters  130  may be used according to the invention as converting units. Such flyback converters  130  are also called isolating transformers. 
       FIGS. 6-8  are described in U.S. patent application Ser. No. 10/489,584 filed Mar. 12, 2004 and entitled DC Converter, which claims the benefit of PCT/EP02/10469 filed Sep. 18, 2002, which claims the priority of DE 201 15 474.9 filed Sep. 19, 2001 (1600-09600; OTE-030455 US), all of which are hereby incorporated herein by reference in their entirety. 
       FIG. 6  shows a simplified embodiment for a push-pull converter  238  used as a switched mode mains power supply  182 . This push-pull converter  238  has its input terminals  192  and  194  connected in series with the other push-pull converters  238  or switched mode mains power supplies  182  according to  FIG. 5 . On the input side, the push-pull converter  238  may comprise a Zener diode  240  and an input capacitor  196 . These two components are connected parallel to each other and to a primary winding  104  of a transformer  92 . 
     The Zener diode  240  can be composed, in a manner known per se, of a number of transistors and load resistors. 
     The primary winding  104  of the transformer  92  has associated therewith a switching means  200 . 
     This switching means  200  is shown as a simple switch in  FIG. 6 . In actual fact, such switching means  200  is, however, realized by one or more switching transistors  222 ,  224 ,  226  and  228 , cf. e.g.  FIGS. 7 and 8 ; such switching transistors may be power MOSFETs, BIMOSFETs or thyristors. 
     The primary winding  104  is magnetically coupled to a secondary winding  106  of the transformer  92 . 
     The secondary winding  106  is connected to output terminals  206  and  212  of the push-pull converter  238 . A diode  202  and a load  204  are serially connected between the secondary winding  106  and the output terminal  206 . The load  204  may e.g. be an inductor  208  according to  FIGS. 7 and 8 . 
     The output terminals  206  of all push-pull converters  238  or switched mode mains power supplies  182  according to  FIG. 5  are connected parallel to one another and to the connection  186 . The other output terminals  212  are also connected parallel to one another and to ground  214 . 
     On the output side of the push-pull converter  238 , a smoothing capacitor  210  is connected parallel to the secondary winding of the transformer  198 . 
     In  FIGS. 7 and 8  a respective push-pull converter  238  according to  FIG. 6  is shown in detail, in one case as a full-bridge push-pull converter  242  and in another case as a half-bridge push pull converter  244 , both push-pull converters  242  and  244  being shown with the respective circuit. Such circuits for full-bridge and half-bridge push-pull converters  242 ,  244  are known per se. The circuits shown differ from known circuits with regard to the respective connection modes of the push-pull converters on the input side and on the output side, i.e. with regard to the fact that respective terminals are serially connected on the input side and connected in parallel on the output side. 
     Furthermore, the Zener diode  240  on the input side of each push-pull converter  238  or  242 ,  244  is connected parallel to the primary winding of the transformer  92 . 
     This Zener diode  240  serves as an input-side load of the various push-pull converters  238  for powering up the system with regard to voltage and energy already prior to connecting or additionally connecting a respective electric device  46 ,  24 . As long as the electric devices  46 ,  24  have not yet been connected or additionally connected, the respective energy in the system is consumed and converted into heat by the Zener diode  240 . When the electric devices  46 ,  24  are then additionally connected, energy distribution takes place in each of the push-pull converters  238 , and it is only a small percentage of the energy that is still converted into heat by the Zener diode  240 . 
     Due to the large number of Zener diodes  240  and the fact that they are arranged in spaced relationship with one another, the electric energy converted into heat in said Zener diodes  240  will not result in overheating of the DC converter  86 , but, depending on the location where the converter is arranged, it can be discharged directly into air or water as waste heat. Complicated and expensive cooling systems can be dispensed with. 
     When the electric devices  46  of remote assembly  25  no longer need electric energy, they will be switched off, i.e. disconnected from the system. Subsequently, the whole energy is, in situ, again converted into heat by the Zener diode  240 . If the electric device  46  in question or another electric device  46  is then not connected or additionally connected once more, the system as a whole can be run down to a lower voltage, such as 3000V or even less than that. The reduced voltage is then still required for the function of the controller and of other units of the DC converter  86  which are always in operation. 
     In the full-bridge push-pull converter  242  according to  FIG. 7  a total of four switching transistors  222 ,  224 ,  226 ,  228  are integrated in the switching means  200 . The switching transistors  222 ,  224 ,  226 ,  228  co-operate in pairs for effecting a push-pull activation of the transformer  92 , the push-pull clock cycle ratio being 1:1. 
     On the output side, respective diodes  202  are provided, and on the input side a plurality of input capacitors  196  are provided. 
     For activating the various switching transistors  222 ,  224 ,  226 ,  228 , a pulse modulation means  230  may be implemented as shown in  FIG. 8 . This pulse modulation means  230  outputs a series of pulses whose widths and/or heights and/or frequencies are variable so as to clock the switching transistors  222 ,  224 ,  226 ,  228 . 
     For the sake of clarity, the pulse modulation means  230  is not shown in  FIGS. 6 and 7 . 
     As previously described, there are electric devices, which require both a high voltage and a high power. If the power and the voltage are suddenly demanded, when the electric device  46  is switched on, and are not yet available, the power and supply assembly  70  may collapse due to a feedback caused by the sudden request or large amount of power. In order to avoid such a collapse and a negative feedback, the clocked switched mode mains power supply  182  has on the input side thereof a load  240  which is connected in parallel to the transformer  92  of such switched mode mains power supply  182 . 
     The DC converter  86  according to the present invention is so conceived that, already prior to switching on or supplying the electric device  46 , the voltage and the power in the control and actuation assembly  80  are increased to at least the values demanded by the electric device  46 . Until the electric device  46  actually operates, the voltage drops across the load  240  and the power is converted into heat as dissipation power. Only when the electric device  46  demands power, will the power across the load  240  be supplied to the electric device  46 . 
     For the DC source, a stable utilization and a constant load are always discernible, i.e., the respective power distribution takes place in situ and is no longer fed back to the supply and control assembly  70 . 
     As described above, the load  240  can be implemented as a Zener diode  240  so that, if necessary, voltage and power can be built up rapidly to desired values only a short time before they are demanded by the electric device. Full voltage and full power can in this way be built up within a few milliseconds and consumed by the Zener diode  240 . The electric device  46  is only connected or additionally connected when voltage and power have been built up completely. The voltage and the power are then supplied to the electric device  46 , only a residual voltage dropping across the Zener diode  240  and only a small percentage of the power (a few percent) being consumed there. If the electric device is then switched off, the whole voltage will again drop across the Zener diode  240  and said Zener diode  240  will consume the full power in the system. Subsequently, the voltage and the power can be reduced to a lower value. The reduced values are sufficient for supplying respective components of the system, such a monitoring and control means, which are also active if no electric device has been connected or additionally connected. 
     If a supply of components by the DC converter  86  according to the present invention is not necessary, the voltage and the power can also be switched off completely or reduced to zero. As soon as there is again a demand from an electric device, voltage and power are again built up within a few milliseconds. 
     In some embodiments, the Zener diode  240  can be implemented in the form of field effect transistors or load resistors. Furthermore, the Zener diode  240  also guarantees in each converter component  182  a good heat dissipation of dissipation power that has there been converted into heat. The heat in question is no longer generated locally within close limits, but it is generated at a large number of locations so that the heat can be given off directly into the air or into water or the like. Separate cooling systems are not necessary. 
     Furthermore, the Zener diode  240  may have a very steep limiting characteristic so as to stabilize the output voltage still further, if necessary. If the Zener diode  240 s and the respective converter components have the same type of structural design, it is also guaranteed that identical current intensities are distributed to each component. The voltage is stabilized up to a range of 2,3 or 5% at the most. 
     In at least some embodiments, to increase a cutoff frequency of the filter  184 , the switch mode power supplies  182  of the DC converting device  86  may be clocked with respect to one another in phase-shifted fashion. 
     To produce corresponding harmonics only to a small degree in this connection, a phase shift in the clocking of neighboring switch mode power supplies  182  may be 1/n each if n is the number of the switch mode power supplies  182  of the DC voltage converting device  86 . Hence, the phase shift is such that the n+1th switch mode power supply  182  would be again in phase with the first switch mode power supply  182  (cyclic phase shift). 
     The switched mode mains power supplies  182  of the DC converter  86  can be clocked in a phase shifted mode so as to shift, especially in the case of the communication connection in the direction of the supply and control assembly  70 , the cutoff frequency of clocking interference. 
     Such a push-pull converter  238  may be designed as a half-bridge or full-bridge push-pull converter  244 ,  242  respectively. In particular for maximum powers the switch mode power supply  182  may be designed as a full-bridge push-pull converter  242 . 
     Such converter components  180  for an input voltage of e.g. a few hundred volts are nowadays commercially available, whereas converter components for a few thousand or for several thousand volts on the input side are not available at all or are at least very expensive and complicated. 
     The parallel connection of the converter components  180  on the output side results, depending on the power of the individual converter components  180 , in the total power of the system. Depending on the total power desired, the number and the structural design of the converter components  180  are selected accordingly. The overall system can easily be adapted to given requirements in this way. 
     In order to satisfy requirements with respect to the control of mains fluctuations and load control, the tendency towards miniaturization and the wish for reducing the dissipation power, the converter components  180  can be implemented as clocked switched mode mains power supplies  182 . Such clocked switched mode mains power supplies  182  have, in comparison with conventional power supply units, an efficiency that is in some cases higher than 90%, a reduction of volume and weight of up to 60%, a voltage stabilization of less than 1-2%, they require only a small amount of filtering means and their price-performance payoff is more advantageous. 
     It can also be considered to be advantageous when the switched mode mains power supply  182  is clocked on the primary side so as to galvanically separate the output side and the input side. 
     The switched mode mains power supply  182  can be implemented as a push-pull converter  238  so as to use a switched mode mains power supply  182  which is also well adapted to high power values. The push-pull converter  238  can be implemented as a half-bridge or as a full-bridge push-pull converter  242 ,  244 . 
     The switched mode mains power supply  182  can include a switching transistor,  222 ,  224 ,  226  and  228  especially a power MOSFET or a power BIMOSFET, so that a transformer of the switched mode mains power supply  182 , which is clocked on the primary side, can be switched electronically in a simple way. In this connection, attention should be paid to the fact that, e.g. for a full-bridge push-pull converter, four such switching transistors  222 ,  224 ,  226  and  228  are respectively connected in pairs. 
     The switching transistors  222 ,  224 ,  226  and  228  can be clocked in a push-pull mode with a clock cycle ratio of 1:1 so as to obtain a low current consumption of the transformer in the push-pull converter. 
     In order to obtain the least possible amount of harmonic waves on the output side, the switched mode mains power supplies  182  of the DC converter  86  can be clocked synchronously. 
     To control the switching transistors accordingly, the switch mode power supply may comprise a pulse modulation means for the clocked control of the switching transistors  222 ,  224 ,  226  and  228 , the pulse modulation means supplying a sequence of pulses of a variable width and/or height and/or frequency for clocking the switching transistors  222 ,  224 ,  226  and  228 . 
     In order to activate the switching means of the various switched mode mains power supplies  182  while controlling or regulating especially the controller, the switched mode mains power supply  182  can be provided with a pulse modulation means which outputs a series of pulses having variable widths and/or heights and/or frequencies so as to clock the switching means in question or rather the switching transistors  222 ,  224 ,  226  and  228  defining the same. 
     A switching means for correspondingly switching the transformer of the switch mode power supply may e.g. be designed as a switching transistor, in particular a power MOSFET or BIMOSFET. It is also possible that the switching means is designed as a thyristor. 
     In a push-pull converter, at least two switching transistors  222 ,  224 ,  226  and  228  are used that operate in the push-pull mode. Advantageously, it is also possible to operate in the push-pull mode with a clock ratio of 1:1. This means that both switching transistors  222 ,  224 ,  226  and  228  are each switched through alternatingly for the same periods of time. 
     To obtain an output voltage that is as smooth as possible and has a relatively small amount of harmonics, the switch mode power supplies  182  of the DC converting device  86  may be clocked in synchronism. This means that all switch mode power supplies  182  are clocked at the same clock rate. 
     To ensure an undisturbed transmission of a communication connection in this respect and to scan the DC voltage on the input side substantially completely at the same time, the clock rate of the switch mode power supply may be in the range of 10 kHz to more than 1 MHz and, in particular, in the range of 50 kHz to 300 kHz. 
     In this connection each switch mode power supply  182  can e.g. be readjusted in its output voltage via changes in the duty factor, in particular, in case of failure of another switch mode power supply  182  of the DC voltage converting device  86 . 
     In the simplest case a readjustment of the output voltage of a switch mode power supply  182  can take place via a change in the duty factor of the switching transistor. 
     To be able to transmit data sent via the cable connection in the direction of the DC voltage source, i.e. without interference and at a high speed, the DC voltage converting device  86  may comprise a filter means  190  arranged upstream on the input side. 
     In connection with the filter means  190 , it should additionally be mentioned that such means filters, in particular, the frequency range within which the communication connection to the DC voltage source takes place. This means that only a lower frequency range of up to e.g. 50 kHz is filtered. Relatively simple and inexpensive filters are thus sufficient. 
     In order to remove interfering frequencies especially from the frequency range required for the communication connection, the DC converter  86  can be provided with a filter means  190  preceding such DC converter  86  on the input side thereof. This filter means  190  filters especially a frequency range of up to approx. 50 kHz. 
     In order to realize suitable communication connection in a simple way and only after the filtering, a means for coupling data signals in/out  136  can be connected upstream of said filter means  190  in the direction of the DC source. 
     It should additionally be pointed out that the filter means  190  between the DC converter  86  and the DC voltage source can be realized e.g. by comparatively small capacitors, since, due to the fact that the individual converter components are clocked in a phase-shifted mode, the cutoff frequency of the system is very high. 
     To monitor, control and regulate the corresponding components of the DC voltage converting device  86  on site, a controller  112  may be assigned at least to the DC voltage converting device  86  and the components thereof. However, the controller  112  may also be responsible for electrical devices supplied by the converting device with DC voltage and may monitor the same in their function and carry out the control or regulation of the devices. 
     The controller  112  used according to the invention can be designed in its monitoring function such that it monitors e.g. the individual switch mode power supplies, reports on the failure of corresponding switch mode power supplies and the location of said switch mode power supplies within the DC voltage converting device  86  and sends an alarm message in case of failure of a predetermined number of switch mode power supplies. The corresponding information of the controller  112  can be transmitted via the coaxial cable connection to the DC voltage source that is located far away, and can be represented there accordingly. 
     A controller  112  can be associated with at least the DC converter  86  and the components thereof so as to design the DC converter  86  in such a way that said DC converter  86  and, if necessary, also the electric device  46  connected thereto can be can be controlled and monitored automatically. This controller  112  can e.g., detect failure of a converter component and, if desired, also the position of said converter component. This information can be transmitted via the communication connection and the means for coupling data signals in/out  136  to the DC source and the units associated therewith. There, the information can be displayed in a suitable manner on a reproduction device, such as a screen or the like. If a relevant number of converter components failed, a repair demand can additionally be supplied by the controller. 
     The cable connection  68  may comprise at least one coaxial cable so that, even if high power is to be transmitted and if voltage and data are transmitted simultaneously, said cable connection can be established such that it has a small cross-section, whereby costs will be saved, especially in the case of long distances. Since the voltage transmitted through the coaxial cable is a DC voltage, only line losses will occur, whereas additional attenuation losses, which are caused by a transmission of AC voltages, are avoided. 
     Referring again to  FIG. 1( c ) , electrical devices  46  or electrical units  24  may be a combination of actuators, sensors, motors, and other electrically operated equipment disposed at a remote assembly  25 . The remote assembly  25  may include a subsea wellhead assembly with a subsea tree. By way of example, the wellhead assembly shown and described in U.S. Pat. No. 6,039,119, hereby incorporated herein by reference, with a spool tree as described therein may be used with the embodiments of the present invention. The subsea tree may also be a dual bore tree. The electrical devices  46  may be actuators, which operate devices such as valves, chokes, and other devices that are used to control the flow of fluid through a subsea system. In the preferred embodiments, the electrically operated subsea system eliminates the use of hydraulically actuated valves. Therefore, control and operation of a subsea assembly  25  can be all electrically controlled. An all electric system offers many advantages, such as quick response, elimination of hydraulic fluid, no dumping of fluid to sea (environmentally friendly), and the ability to perform real time diagnostics on the actuators, valves, and chokes of the assembly  25 . At the surface, the requirement for a hydraulic power unit is eliminated and the surface equipment can be packaged more compactly. 
     The following embodiments describe exemplary electrical devices  46  and electrical units  24  that may be used with the electric control and supply system  60  of the present invention. 
     Referring now to  FIG. 9 , there is shown a section through an electrical device  46  of a remote subsea assembly  25 . The electrical device  46  is an actuator system  250  constructed in accordance with U.S. patent application Ser. No. 10/276,204, filed Nov. 12, 2002 and entitled Actuating Device, which claims the benefit of PCT/EP01/05156 filed May 7, 2001, which claims the priority of DE 200 08 415.1 filed May 11, 2000 (1600-07500; OTE-030295); all of which are hereby incorporated by reference herein in their entirety. Actuator system  250  is mounted via flange housing  286  to a control device  252  in the form of a gate valve. The actuator system  250  includes a system enclosure  254  laterally flanged to one side of the control device  252  with an actuator element  260  slide-mounted in the axial direction  256  to permit shifting between an extended position  262  and a refracted position  264 . The actuator element  260  is connected to a valve slide  258  that is reciprocably disposed within the control device  252  so that the valve slide  258  can be shifted in the shift direction  276 . 
     In the extended position  262 , the actuator element  260  is extended so as to shift the valve slide  258  within a slide bore  270  of the control device  252  to a position where it opens a transverse flow bore  272  through the valve gate  252  and through the valve slide  258 . In its retracted position  264 , the valve slide  252  closes the flow bore  272  through the valve gate  252 . At least one return spring  266  is mounted on the other side of the control device  252  to subject the actuator system  250  to a pressure load in the reset direction  268 . A connecting line  280  connects the actuator system  250  with the control and actuation assembly  80 . The connecting line  280  is used for controlling the actuator system  250  and for data transfer. 
     Referring now to  FIG. 10 , there is shown a longitudinal section through the actuator system  250 . In the upper half of  FIG. 10 , the actuator element  260  is shown in its retracted position  264  and in the lower half, separated by the axis line  256 , the actuator element  260  is shown in its extended position  262  as in  FIG. 9 . 
     The enclosure  254  is a two-part system having an inner enclosure section  282  removably attached to an outer enclosure section  284 . The outer enclosure section  284  houses a power assembly  290  including an electric motor  292 , for instance a direct-current servomotor, that is connected to a drive assembly  294 , which may comprise a standard clutch-and-brake combination or alternatively a so-called flex-spline drive without the traditional gears. It should be appreciated that motor  292  preferably uses DC voltage but may use AC voltage. Power is supplied to motor  292  by subsea power source  102  via a connecting lines such as line  186 . Connecting sleeve  298  is connected to drive assembly  294  on one end and to ball nut  306  at its opposite end. Rotating spindle  310 , in the form of a ball screw  312 , is suspended in the ball nut  306  and is adapted to move relative to the ball nut along axial direction  256 . The drive assembly  294  turns the connecting sleeve  298  and the rotation is transferred to the ball nut  306 , causing the rotating spindle  310  translate relative to the ball nut  306 . 
     A positional sensor  295  is disposed on the outer end section  284  to detect the longitudinal position of the spindle  310 . The positional sensor  295  protrudes from the enclosure end section  284  and is positioned inside a sensor cap  316  that is detachably connected to the enclosure end section  284 . The sensor  295  would detect for instance the respective longitudinal position of the rotating spindle  310  from which it determines the position of the actuator element  260 . 
     At its end on the side of the rotating spindle  310 , the actuator element  260  is connected to a rotary mount  338 . Radially protruding from the rotary mount  338  are two mutually opposite guide lugs  342  which engage in corresponding guide slots  344  in the rotating sleeve  330  and are guided by these slots in the axial direction  256 . By engaging in the guide slots, the guide lugs cause the rotary mount  338  and thus the rotating spindle  310  and the rotating sleeve  330  to be rigidly connected to one another. 
     Volute spring  318  permits rotation of the connecting sleeve  298  in the advance direction  320  while preventing any rotation in the reverse direction. A second volute spring  332  is disposed between casing  324  and rotating sleeve  330 . At one of its coil ends, the volute spring  332  makes contact with an inside surface of a tensioning sleeve  356  that engages in a gear  362  that is turned by a tensioning motor  364 . The tensioning motor  364  is positioned between the casing  324  and the system enclosure  254  and can be controlled independent of the electric motor  292  for turning the tensioning sleeve  356 . The tensioning motor  364  is connected to the control and actuation assembly  80 . 
     A return spring  366  in the form of a torsion spring is connected to tensioning sleeve  356  such that, when the tensioning motor  364  turns the tensioning sleeve  356 , it tensions the return spring  366 , producing the necessary return force for the tensioning sleeve  356 . The combination of tensioning motor  364 , tensioning sleeve  356 , volute spring  332  and return spring  366  constitutes an emergency release unit  370  which causes the actuator element  260  to be automatically reset into its refracted position  264  in the event of an electric-power failure in the actuator system  250 . 
     In operation, the actuator element  260  is moved in the shift direction  276  by operating the electric motor  292 , which, by way of the drive assembly  294 , turns the connecting sleeve  298  and the ball nut  306 . As the ball nut  306  turns, the rotating spindle  310  or ball screw  312  is moved in an axial direction  256  which, by way of the rotary mount  338 , moves the actuator element  260  in the direction of the extended position  262 . The corresponding longitudinal movement of the rotating spindle  310  is monitored by the positional sensor  295 . As shown in  FIG. 2 , with actuator element  260  in the extended position  262 , the valve  252  is open, allowing gas, oil or similar exploration or extraction to take place. 
     Either simultaneous with or before operation of motor  292 , tensioning motor  364  turns the gear  362  and with it the tensioning sleeve  356 , causing the volute spring  332  to be relaxed and the return spring  366  to be tensioned. If and when the tensioning motor  364 , designed as a step motor, is fed a corresponding holding current by control and actuation assembly  80 , it will hold its position, as will the tensioning sleeve  356 . The return spring  366  stores energy which tries to turn the tensioning sleeve  356  back against the holding force of the tensioning motor  364 . 
     If the actuator element  260  is to be moved, the holding force of the tensioning motor  364  is brought down by appropriate controls in control and actuation assembly  80 . This will then release the volute spring  332 , enabling the rotating sleeve  330 , powered by the return energy of the return spring  366 , to rotate in the opposite direction relative to the casing  324 . By virtue of the rigid connection between the rotating sleeve  330  and the rotating spindle  310 , provided by the guide slots  342  and guide lugs  344 , the rotating spindle  310  and ball nut  306  can reverse direction toward the electric motor  292 , whereby the actuator element  260 , connected to the rotating spindle  310 , is shifted back into its retracted position  264  (see  FIG. 9 ). A major factor in this context is the return force applied by the return spring  366  on the actuator element  260  since it is essentially this force that resets both the actuator element  260  and the rotating spindle  310  by turning back the tensioning sleeve  356  and correspondingly releasing the volute spring  332 . 
     In the event of a power failure as well, the holding force in the tensioning motor  364  subsides, causing an emergency closure of the actuator system  250  due to the action of the return spring  366 , volute spring  332  and tensioning sleeve  356 . As described further above, the return spring  366  turns the tensioning sleeve  356  back, releasing the volute spring  332 , so that the rotating sleeve  330  can then rotate relative to the casing  324 . The remainder of the closing process takes place in the same way as in a normal closing operation of the actuator system  250 . 
       FIG. 11  is a frontal illustration of the actuator system  250  per  FIG. 10  viewed in the direction of the outer enclosure end section  284  and the sensor cap  316 .  FIG. 10  represents a sectional view along the line II-II in  FIG. 11 . Four compensators  372 , shown in more detail in  FIG. 12 , are mounted in a concentric arrangement around the positional sensor  295  per  FIG. 11 .  FIG. 12  represents a section along the line IV-IV in  FIG. 11 . The compensators  372  are positioned in the outer enclosure end section  284  in a radial configuration relative to the electric motor  292 . These compensators  372  serve to compensate for volume and pressure variations relative to a complete oil filling of the actuator system  250 , i.e. they compensate for volume changes due to system actuation and to temperature fluctuations. 
     Referring now to  FIGS. 13 and 14 , actuator system  250  may also include an externally activated emergency actuator assembly  378  in accordance with U.S. patent application Ser. No. 10/276,201, filed Nov. 14, 2002 and entitled Actuating Device which claims the benefit of PCT/EP01/05158 filed May 7, 2001, which claims the priority of DE 200 08 414.3 filed May 11, 2000 (1600-07400; OTE-030297), all of which are hereby incorporated by reference herein in their entirety. The emergency actuator  378  includes an auxiliary trunnion  380 , with diametrically opposite pins  381  for attaching from outside the actuator system  250 , such as with an underwater manipulator or similar tool. Auxiliary trunnion  380  may be located adjacent to position-monitoring sensor  295 .  FIG. 13  shows an end view of system  250  while  FIG. 14  shows a longitudinal section along the line A-C in  FIG. 13 . 
     The motor  292  and the tensioning motor  364  each feature, respectively, a motor shaft  382  or a tensioning-motor shaft  404 , projecting toward trunnion  380 . Motor shaft  382  is equipped with a gear  388  in the form of a free-wheeling gear with a coaster mechanism  390 , thus constituting a directional clutch unit  392 . The free-wheeling gear  388  engages in a drive gear  395 , which is mounted on one end of the trunnion  380 , with a slip-ring coupling  394  interpositioned between them. 
     Tensioning-motor shaft  404  connects to a sleeve nut  406  that supports a tensioning gear  414 . As can be seen in  FIG. 13 , tensioning gear  414  is rotated by the rotation of trunnion  380  via drive gear  395  and intermediate gear  418 . Therefore, rotation of trunnion  380  rotates both a motor shaft  382  and a tensioning-motor shaft  404 . 
     The combination of auxiliary trunnion  380 , drive gear  395 , free-wheeling gear  388 , tensioning gear  414 , and tensioning motor shaft  404  forms and emergency actuator assembly  378  by means of which, in the event power to the motor  292  or to the tensioning motor  364  is interrupted or some other problem interferes with the normal operation of the actuator system  250 , the actuator element  260  can be shifted into its operating position  276  as described above. 
     The emergency actuator assembly  378  and its components remain in an idle standby state during normal operation, without requiring any further technical provisions, i.e. they are not moved in any way. If in an emergency situation the actuator element  260  is to be opened by the emergency actuator assembly  378 , the auxiliary trunnion  380  is turned in the appropriate direction, in this case also turning the motor  292  by way of the free-wheeling gear  388  and coaster mechanism  390 , as a result of which the actuator element  260  is shifted into its extended position  262 , as described above. 
     At the same time, by way of the intermediate gear  418  and the tensioning gear  414 , the tensioning motor  364  is set in motion to activate the emergency release unit  370 . The emergency release unit  370  is so designed that after only a few hundred revolutions of the tensioning-motor shaft  404 , the volute spring  332  and return spring  366  are tensioned and by virtue of the slip-ring coupling  416 , any further torque action on the tensioning motor  404  is prevented. 
     If in an emergency situation the actuator system  250  must be used to close the actuator element  260 , the auxiliary trunnion  380  is turned in the opposite direction. Only a few turns are necessary to trigger the emergency release unit  370 . That unit  370  then works as described above, without the motor  292  turning along with it since in this case again the free-wheeling mechanism is activated. 
       FIG. 15  illustrates one embodiment of a position measuring sensor  295  as described in U.S. patent application Ser. No. 10/344,921, filed Feb. 18, 2003 and entitled Method and Device for Measuring a Path Covered which claims the benefit of PCT/EP01/09513 filed Aug. 17, 2001, which claims the priority of EP 00117841.7 filed Aug. 18, 2000 (1600-07700; OTE-030305), all of which are hereby incorporated by reference herein in their entirety. In order to determine the position of a control element relative to a housing in the case of such a linear control device relative to the housing, one end of the control element may be connected with a spring element, which, with its end turned away from the control element, is connected with a force-measuring device, which transmits an electrical signal corresponding to the force transmitted from the spring element to the force-measuring device, to an evaluating device. This means that the linear control device is distinguished by the fact that the path-measuring device is incorporated in the latter. Correspondingly the path-measuring device in the linear control device can have the same features as the position-monitoring sensor described below. 
     In the case of oil and gas recovery, in particular, a number of linear control devices are used. Such a linear control device is used, in particular, for operating valves, throttles or the like, in the case of oil and/or gas recovery, and has at least one control element mounted movable linearly within a housing and a drive device associated with the latter. The control element may be a ball spindle, which is mounted capable of turning in a corresponding nut. The nut is connected moving with the corresponding drive device and converts rotation of the nut induced thereby into a longitudinal motion of the ball spindle. 
     The position-monitoring sensor  295  has a simple, strong, and reliable construction and is particularly suited for applications in remote and inaccessible areas. For example, one area of application is the use of the position-monitoring sensor  295 , for the linearly actuator element  260  in a device for oil and/or gas production. Corresponding devices are so-called actuators, BOP&#39;s (blowout presenters), valves and the like, as are necessary in the case of oil and gas production. In this case, the area of application of the position-monitoring sensor  295  is not limited to uses on land, but because of the insensitivity to pressure or other unfavorable environmental influences, in particular the use under water is also possible. This obtains analogously for underground use. 
     Referring now to  FIG. 14 , the position-monitoring sensor  295  is situated underneath the auxiliary trunnion  380  and is operationally connected to the motor shaft  382  of electric motor  292  that is rotatable in the direction of advance rotation  320 . Located next to the positional sensor  295 , in the same recess in the motor cover or end section  284  is the plug connector  384  for the connection of a connecting line by way of which data can be transmitted to or retrieved from the position-monitoring sensor  295  and actuator system  250  and power may be provided to power assembly  290 . 
     Referring now to  FIGS. 15-17 , there is shown an enlarged view of the position-monitoring sensor  295  as an example of path-measuring device according to the invention. The position-monitoring sensor  295  is located in a linear drive device  450 , which has at least one operating element  452 , which is movable back and forth in the longitudinal direction. Operating element  452  is preferably a ball spindle, which is mounted capable of rotating in a ball rotation nut. At the time of the rotation of the ball rotation nut by means of the drive device  450 , shown only partially in  FIG. 15 , there is a corresponding rotation of the operating element  452  and a motion of the operating element  452  in the longitudinal direction takes place as a result of the rotation relative to the ball rotation nut in the longitudinal direction. 
     Operating element  452  is connected at one end  454 , per  FIG. 15 , with spring element  456  of position-monitoring sensor  295 . The spring element  456  is guided in a conduit  458  by drive device  450  and connected with its end opposite the operating element  452  with a corresponding force-measuring device  460  in the form of an electrical measuring conductor. The force exerted by the operating element  452  onto spring element  456  by means of the force-measuring device  460  or the corresponding electrical measuring conductor is converted into a corresponding voltage. 
     The spring element  456  can be chosen in particular so that it expands proportional to the retaining force exerted, so that the evaluation of the signal of the force-measuring device  460  and correspondingly the determination of motion or position of the actuator element  260  is simplified. 
     Since a spring element, as a rule, has a soft damping characteristic, corresponding vibrations, shocks, or the like are transmitted without influence on the force-measuring device  460 . 
     Such a spring element  456  can be chosen with the corresponding spring constants, from corresponding material, and the like depending on the requirements. Only a limited motion of the actuator element  260  is possible because of the connection with the spring element  456  and via the latter with the force-measuring device  460 . Essentially the range of motion is determined by the spring element  456  and the maximum expansion, which can be evaluated by the latter. 
     The spring element may follow a curved, for example circular, path of a moving object, and correspondingly the position of the moving object along this path can be determined. 
     Force-measuring device  460  can include a number of electrical conducting wires, which change their resistance depending on the force exerted on them. This means, a resistance change of the electrical conducting wires corresponds to a force transferred by spring element  456 , and the force is proportional to a deflection of spring element  452  and thus to a position of the longitudinal movement of actuator element  260 . 
     The wires of force-measuring device  460  are parallel to another and can be switched electrically also parallel or even in series. The wires form a resistor, which is part of a bridge circuit, as shown in  FIG. 18 . A further resistor  462  of this bridge circuit also is formed by a number of electric conducting wires and this further electrical resistor  462  corresponds to the resistance formed by the electric conducting wires of force-measuring device  460  and is used for temperature compensation. 
     In order to be able to determine changes in the resistance in such an electrical conductor  460  in a simple way, the electrical conductor  460  can be connected in a bridge circuit, such as a so-called Wheatstone bridge, and form at least one resistor in the bridge circuit highly accurate circuit measurements are possible by means of such a bridge, whereby a high accuracy for position determination of the actuator element  260  also results. 
     In order to compensate for changes in the resistance of the conductor  460 , on the basis of temperature changes, so that the latter do not lead to an erroneous determination of the position of the moving object, the bridge circuit can have a further resistor analogous to the resistor formed by the force-measuring device  460 . For example, if the force-measuring device  460  is made up of a number of wires, this further resistor is made in a similar way. Of course, as opposed to the force-measuring device  460 , it is not exposed to a corresponding tensile force from the spring element  456 . 
     In order to compensate for certain statistical irregularities of the wire, such as diameter deviations, changes in the properties of the material, and so forth, in a wire-like conductor  460  in a simple way, the conductor  460  can have a number of electrically conducting wires located parallel to one another. In this way, corresponding statistical deviations of the individual wires are determined and a force-measuring device  460  measuring accurately over its entire measuring range results. 
     The wires may be individual wires or formed by an individual wire, which is laid meandering. 
     The force-measuring device  460  has at least one electrically conducting, in particular wire-like conductor, the electric resistance of which depends on a force exerted upon it in the longitudinal direction. Such a conductor also may be made out of different materials, which are chosen, for example, with respect to the environmental conditions under which the position-monitoring sensor  295  is used. In this way the position-monitoring sensor  295  also may be used in aggressive media, under water, under pressure, under a vacuum and the like, essentially without limitations. Because of a simple structure of the position-monitoring sensor  295  there is no wear and no abrasion of the individual parts, so that the service life is extraordinarily high. 
     Such an electrical conductor  460  as a force-measuring device changes its electrical resistance in the case of exertion of a corresponding tensile force on the conductor, and such a resistance change can be detected via corresponding stress or current changes and evaluated as a signal in the evaluating device  468 . 
     The force-measuring device  460  can be made correspondingly in order to convert the tensile force exerted by the spring element  456  into an electrical signal. A simple example of such a force-measuring device  460  can be seen if the latter has at least one electrical measuring conductor, the electrical resistance of which changes depending on a force exerted on the measuring conductor. 
     An offset device  464  and amplifier  466  are connected with the resistors formed by the wires. Corresponding signals from the amplifier  466  may be output on an output unit of evaluating unit  468 , in which case this evaluating unit  468  also can have a differentiator, by which the corresponding position values of actuator element  260  changing in time can be differentiated and thus a speed and, in a given case, acceleration, of the actuator element  260  can be determined. 
     A zero point of the deflection of the spring element  456  can be adjusted by offset device  464 . For example the springs can be pre-stressed 2% to 5%, in order to create such a measurable zero point for the motion of the actuator element  260 . A stress value associated with this pre-stress is set to zero by means of the offset device  464 . 
     A voltage supply is connected with the wires and the evaluating unit for the voltage supply of the wires and evaluating device. 
     In the case of a linear control device which has a control element moving linearly forward by a screw motion, it is advantageous if the corresponding turning of the control element is not transferred to the spring element and thus leads to a stress or force in the spring element, which is not caused by the linear motion of the control element. For this, for example, at least the connector between spring element and control element can have a rotation decoupling device. Only the linear motion of the control element is transferred to the spring element by means of this rotation decoupling element, and the rotation is received by the rotation coupling device. 
     The spring element  456  according to  FIGS. 15-18  is connected via connectors  470 ,  472  to control element  452 , respectively with electrical measuring conductor  460 . The connector  470  is a rotation decoupling device  469 . The rotation decoupling device  469  prevents a transfer of the rotation of the operating element  452  made as a ball spindle to spring element  456 . Rotation decoupling device  469  can be made, for example, by a screw which is screwed into the end of operating element  452 , and which is mounted fixed capable of rotating in the connector  470 , but in the longitudinal element of the spring element  456 . 
       FIG. 16  corresponds to a magnified representation of section “X” from  FIG. 15  and  FIG. 17  is a magnified representation of section “Y” from  FIG. 15 . 
     The connection of spring element  456  with the connector  472  in particular is shown in  FIG. 16 . This is connected to electrical measuring conductor  460 , which is fastened on its end opposite spring element  456  at a fixed point of housing  474  of linear control device  476 . Corresponding connecting wires are connected to the electrical measuring conductor  460  via soldering points, which lead to the bridge circuit  481 , see  FIG. 18 . 
     In order to be able to detect corresponding resistance changes easily via associated stress changes, the electric measuring conductor  460  can be connected as a resistor in a bridge circuit, as a so-called Wheatstone bridge. 
     According to the invention a simple electrical structure, which also requires simple means in the case of the evaluating unit  468 , results from the use of the bridge circuit and the electrically conducting wires  460  as a force-measuring device. For example, an amplifier  466  and/or a differentiator and/or an evaluating device  468 , connected with a microprocessor or the like, are the only electronic components, which are necessary. The differentiator may be omitted if, for example, a determination of the speed or acceleration of the actuator element  260  during this motion is omitted. In addition, arrangements of other evaluating devices are used if the latter are supported by software. 
     The signals detected are transferred to evaluating device  468  from the bridge circuit  481  via the amplifier  466  for further processing. 
     One branch of the bridge circuit is grounded and the other branch lies on the plus pole of a voltage source. 
     In operation the linear motion of the actuator element  260  can be measured as a result of the fact that a retaining force is exerted by the spring element  456  during motion of the actuator element  260 . Of course this is so small that it does not hinder, or only slightly hinders the desired motion of element  260 . The retaining force exerted by spring element  456  is transferred to an electrical conductor as a force-measuring device  460 . The electrical conductor  460 , for example, has a number of wires, the resistance value of which varies in the case of exertion of a tensile force in a longitudinal direction of the wires. The change of the resistance value is determined by a corresponding change of a voltage decreasing on the resistor, this resistance change and thus also the associative voltage. change depending on the force exerted. If the force which is exerted by the spring element  456  onto actuator element  260  is determined from the resistance changes by corresponding calculations, the deflection of the spring  456  and thus the position of actuator element  260  may be determined simply from the force if the corresponding parameter (spring constant) of spring element  456  is known. 
     The actuator element  260  moves against the resistance of the elastically expandable retaining element  456  along an essentially linear path, having the retaining force appearing in the retaining element  456  be measured in relation to the path covered by the actuator element  260  and a signal corresponding to the retaining element  456  be transmitted from the force measuring device  460  to an evaluation device  468 , and the path covered by the actuator element  260  corresponding to the retaining element  456  be determined there. 
     The spring element  456  is expanded in the case of motion of the actuator element  260 , the retaining force appearing in the spring element  456  in the simplest case is directly proportional to the path covered by the actuator element  260 . The retaining force is transferred through the spring element  456  to the force measuring device  460  and measured there. A corresponding electrical signal, which corresponds to the retaining force, and thus to the path covered by the actuator element  260 , is received by the evaluation device  468  connected with the force-measuring device  460 . 
     The components used for the position-monitoring sensor  295  are designed simply and economically. No wear of these components takes place, since, for example, there is no friction between the components or between the components and other objects. The position-monitoring sensor  295  is independent of a medium in which it is located, of the site conditions, of vibrations, shocks, or the like. 
     Referring now to  FIGS. 19-21 , there is shown a dual redundant actuator  480  shown in schematically for actuating an actuation system  250 . Dual redundant actuator  480  is constructed in accordance with U.S. patent application Ser. No. 10/415,419, filed Mar. 29, 2003 and entitled Actuating Device, which claims the benefit of PCT/EP01/12551 filed Oct. 30, 2001, which claims the priority of DE 200 18 564.0 filed Oct. 30, 2000 (1600-08200; OTE-030327), all of which are hereby incorporated by reference herein in their entirety. The dual redundant actuator  480  includes a power assembly  290  having two separate electric motors  292   a ,  292   b . The electric motors  292  are preferably direct current servomotors and are both used, where necessary, independently of one another for rotating the drive shaft  382 . As best shown in  FIGS. 20-21 , when the drive shaft  382  is rotated, a rotating spindle  310  is displaced in the regulating direction  482  and accordingly the actuating element  260  connected to it is also displaced. The actuating element  260  is used, for example, for closing or opening a valve as control device  252 , shown in  FIG. 9 , to be actuated by the dual redundant actuator  480  of actuating system  250 . 
     The servomotors  292   a ,  292   b  may be each electrically connected to a dedicated motor control device  484  or  486 . These devices  484 ,  486  comprise appropriately a microprocessor, a memory device and other components necessary for the control, such as controller  112 . An appropriate software program for controlling the servomotors  292   a ,  292   b  is held in the motor control devices  484 ,  486 . Each of the electric motors  292  may be individually and essentially independent of one another. 
     Each of the motor control devices  4894 ,  486  can be separately connected to the dual redundant actuator  480  via suitable connections  487 ,  488  (see for example  FIG. 20 ). In addition, each of the motor control devices  484 ,  486  is connected to a suitable voltage supply, such as supply  102 . 
     In order to supply the motors  292  of the actuating device  250  with electricity also independently of one another at least two separate electrical connections  487 ,  488  are arranged on the housing  254  and especially on the housing cover  488  adjacent to the electric motors  292 . The appropriate voltage supply as well as the data interchange or interchange of control signals can be implemented via these electrical connections  487 ,  488 . Each of the electrical connections  487 ,  488  can be provided for one of the electrical motors  292 , i.e. servomotors. In this connection it is also possible that each of the electrical connections  487 ,  488  is assigned to a stepper motor  364 . A further possibility is also the provision of separate electrical connections for the stepper motors  364 . 
     According to the invention, there is the possibility that the two electric motors  292  can be controlled independently of one another for the separate drive of the drive shaft  382 . In this case it is practicable to operate one of the electric motors  292  in the idling mode when the other drives the drive shaft  382 . 
     However, in order to be able to transfer a higher torque to the drive shaft  382  when necessary and therefore to displace the actuating element  260  in the regulating direction  482  with a higher force, both electric motors  292  (servomotors) can be operated simultaneously. 
     In this case, in order to prevent the motors  292  from rotating the drive shaft  382  with a phase displacement due, for example, to different motor characteristics or due to the formation of the separate electrical supply for both motors  292  instead of providing mutual support during simultaneous operation, the servomotors  292  can be especially synchronized by software via their associated motor control devices  484 ,  486 . 
     A simple type of synchronization and control can be seen in that one servomotor  292  is used as the master and the other as the slave. 
     It can be seen as being advantageous, especially for the transmission of a high torque if each of the servomotors  292  is a direct current motor. 
       FIG. 20  shows a front view of a housing cover  490  of a device housing  284 , see  FIG. 21 , of the dual redundant actuator  480  according to the invention. The housing cover  490  can also be the end of a sub housing, see  FIG. 21 , which can be releasably connected to the rest of the housing  254 . 
     In the housing cover  490  especially the connections  487 ,  488  for the electrical supply and control of the servomotors  292   a ,  292   b  are arranged. A smaller cover  492  is arranged centrally with respect to the housing cover  490 , the smaller cover  492  covering a pot-shaped protrusion of the housing cover  490 , see again  FIG. 21 , in which a position sensor  295  is located. 
     For the further monitoring of the actuating device  250  according to the invention, especially remotely from said actuating device  250 , a position sensor  295  can be assigned to the drive shaft  382 . With the sensor  295 , it can be found, for example, how far the actuating element  260  has been regulated, whether it has returned to its initial position, etc. 
       FIG. 21  shows a section along the line IV-IV from  FIG. 20  with the addition of connector  488 . 
     The two servomotors  292   a ,  292   b  of the drive device  290  are arranged in the longitudinal direction  276  of the drive shaft  382  one behind the other. The drive shaft  382  extends adjacent to the position sensor  295 . The sensor  295  is used to measure rotation of the drive shaft  382  and therefore for the determination of a feed of the actuating element  260  in the regulating direction  482 . An especially simple and space-saving arrangement can be seen in that the electric motors  292  are arranged one behind the other in the longitudinal direction  276  of the drive shaft  382 . 
     The drive shaft  382  terminates in a transmission device  494 , which, for example, can be a so-called flex-spline gearbox without classical gearwheels. A rotating sleeve  496  is rotated by the drive shaft  382  via the transmission device  494 , the rotating sleeve  496  being rotationally rigidly connected to a ball nut  306  as part of a feed device  314 . A further part of the feed device  314  is formed by the rotating spindle  310 , which is a recirculating ball spindle. 
     A spindle head  340  is arranged on one end of the rotating spindle  310 , which protrudes from the ball nut  306 . The actuating element  260  is connected to the spindle head  340  on its side opposite the rotating spindle  310 . The rotating sleeve  496  is rotationally supported in the ball bearing  358  with respect to a retaining sleeve  326 , which surrounds the rotating sleeve  496 . The rotating sleeve  496  is inserted into a ring flange  300  at its end facing the transmission device  494 . 
     In order to prevent reactions by the control device  484 ,  486 , which is subjected to force in the direction opposite to the regulating direction  482 , via the actuating element  260  and rotating spindle  310  or recirculating ball spindle on the electric motors  292 , the rotating sleeve  496  can be fixed by a first spiral spring  318  opposing a feed rotational direction on a ring flange  300  rotationally rigidly arranged in the housing  254 . The feed rotational direction corresponds here to a rotation of the recirculating ball spindle for the regulation of the actuating element  260  or the rotating spindle  310  in the regulating direction  482 . 
     In order to enable resetting of the actuating element  260  in the direction opposing the regulating direction  482  despite this when the control of the actuating device  250  fails, a retaining sleeve  326  can be rotationally rigidly connected at one of its ends to the transverse wall  296 , whereby the retaining sleeve  326  is rotationally rigidly connected at its other end via a second spiral spring  332  to a guide sleeve  330  in the direction opposite to the feed rotational direction, the actuating element  260  connected to the recirculating ball spindle being supported for longitudinal displacement, but rotationally rigidly in the guide sleeve  330 . If this second spiral spring  332  is released during a failure of the usually provided control for the actuating device  250 , the guide sleeve  330  can rotate in the direction opposite to the feed rotational direction due to the force which is transferred via the actuating element  260  and which is acting on the control device  252  to be actuated. Through this rotation the rotating spindle  310  is turned back in the recirculating ball nut  306  also in the direction opposite to the regulating direction  482  until the actuating element  260  is again arranged in its initial position. 
     In this connection, in order to prevent the actuating element  260  itself from being rotated in the direction opposite to the regulating direction  482  when being displaced, a spindle head  340  for mutual connection can be arranged between the actuating element  260  and the recirculating ball spindle. The actuating element  260  is decoupled with regard to rotation from the recirculating ball spindle by this spindle head  340 . 
     In order to wind up the second spiral spring  332  for the rotationally rigid connection of the retaining sleeve  326  and guide sleeve  330  sufficiently tightly on them, the spring  332  can be drive-connected to at least one electric motor  292 . A sufficiently rotationally rigid connection between the retaining sleeve  326  and the guide sleeve  330  is produced by suitable actuation of the electric motor  292  for winding up the spiral spring  332 , especially before regulation of the recirculating ball spindle and actuating element  260 . 
     In order to enable appropriate guidance and retention with regard to the guide sleeve  330  as mentioned above, the spindle head  340  can comprise at least one guide element  497  protruding radially outwards, which engages a longitudinal guide  498  running in the guide sleeve  330  in the regulating direction  482 . 
     In order to be able to still release the second spiral spring  332  with the failure of both electric motors  364 , a torsion spring  366  can be arranged between the clamping sleeve  499  and ring flange  336 , the torsion spring  366  being able to be tensed during the rotation of the clamping sleeve  499  for winding up the second spiral spring  332 . If therefore the clamping sleeve  499  is no longer held by one of the electric motors  364  during the failure of its electrical supply in such a position in which the second spiral spring  332  is wound up, the torsion spring  366  rotates back the clamping sleeve  499  at least so far that the second spiral spring  332  is relieved for the release of the rotationally rigid connection between the retaining sleeve  326  and the guide sleeve  330 . 
     In order to be able to finely and accurately control the rotation of the clamping sleeve  499 , the first and second electric motors  364   a ,  364   b  can be stepper motors. The electric motors  292  and  364  may be powered by either DC or AC voltage, preferably DC voltage. 
     A first spiral spring  318  is wound up on the outer sides of the ring flange  300  and the rotating sleeve  496 . The spring  318  is used to provide the rotationally rigid connection of the ring flange  300  and the rotating sleeve  496  in a rotational direction opposite to the feed rotational direction of the rotating sleeve  496 , i.e. the direction of rotation through which both the rotating spindle  310  and also the actuation element  260  are displaced in the regulating direction  482 . 
     The ring flange  300  protrudes essentially coaxially to the drive shaft  382 , respectively rotating spindle  310  from a transverse wall  296 . The wall  296  is arranged in the region of the housing  254  where it is releasably connected to the sub housing  284 . 
     A retaining sleeve  326   a  is rotationally rigidly connected to the transverse wall  296  radially outwards relative to the ring flange  300 . The rotationally rigid connection is realized by screwing one end of the retaining sleeve  326   a  to the transverse wall  296 . The retaining sleeve  326   a  extends up to its end, which faces away the transverse wall  296 . The retaining sleeve  326   a  is rotationally supported relative to a guide sleeve  330  on this said end via a ball bearing  258 . A second spiral spring  332  is wound up on the outsides of both the retaining sleeve  326   a  and also the guide sleeve  330 . 
     The guide sleeve  330  extends to a housing cover  334  through which the actuating element  260  is passed. The guide sleeve  330  exhibits longitudinal guides  497  running in the regulating direction  482  and in which guide elements  498  engage. The guide elements  498  protrude outwards radially from the spindle head  340 . 
     In the region of the longitudinal guides  497 , the guide sleeve  330  is inserted into a ring flange  336 , which protrudes from an inner side of the housing cover  334 . A clamping sleeve  499  is rotationally supported by suitable bearings on an external side of the ring flange  336  and on an external side of the retaining sleeve  326 . The clamping sleeve  499  is releasably connected at its end facing the drive device  290  by screwing to a toothed ring  491 . The toothed ring  491  exhibits inner teeth as tooth system  493 , which engages the gearwheels  362   a ,  362   b . The gearwheel  362   a  can be rotated by a first electric motor  364   a  and the other gearwheel  362   b  by a second electric motor  364   b . The electric motors  364  are preferably stepper motors. 
     In order to be able to accommodate the appropriate electric motor  364  at a convenient point within the housing  254 , the electric motor  364  can be drive-connected to a clamping sleeve  499  from which a dog  495  protrudes radially inwards which can be motion-connected to essentially one end of the second spiral spring  332 . Due to the arrangement of the clamping sleeve  499 , the electric motor  292  can be located remotely with respect to the second spiral spring  332 . Here, the arrangement is preferably realized such that a space available in the housing  254  is optimally used. 
     In order to be able to arrange the actuating device  250  suitably compact and with small outer dimensions, the clamping sleeve  499  can be rotationally supported on an external side of the retaining sleeve  326  and on an external side of a ring flange  336  which engages in the housing  254 , whereby the ring flange  336  protrudes from an inner side of a housing cover  334 . 
     A simple type of drive connection between the electric motor  364   a  and clamping sleeve  499  can be seen in that the electric motor  364   a  drives a gearwheel  362   a , which engages teeth on especially one end of the clamping sleeve  499 . 
     In order to achieve redundancy also in connection with the drive of the clamping sleeve  499 , another electric motor  364   b  can be arranged, especially diametrically opposed to the first electric motor  364   a , through which a gearwheel  362  that meshes with the teeth can be driven. In this way the clamping sleeve  499  can be alternatively driven by the first or second electric motor  364   a ,  364   b  and especially with the failure of one electric motor the other one is used. 
     A dog  495  protrudes radially inwards approximately centrally to the clamping sleeve  499  and the dog  495  can be coupled to one end of the second spiral spring  332 , so that, depending on the rotation of the rotating sleeve  496 , the second spiral spring  332  can be wound up more or less on the retaining sleeve  326  and the guide sleeve  330 . 
     A torsion spring  366  is arranged between the clamping sleeve  499  and ring flange  336 . The spring  366  can be clamped between the ring flange  336  and the rotating sleeve  496  when the clamping sleeve  499  is rotated for winding up the second spiral spring  332 . 
     The following describes the function of the dual redundant actuator  480  in accordance with  FIGS. 19-23 . 
     Since the servomotors  292   a ,  292   b  are mounted on the drive shaft  382 , they can be used singly as well as in combination. Single application occurs especially when one of the servomotors  292   a ,  292   b  is to replace the other one. Common actuation of both servomotors  292   a ,  292   b  is especially then provided when a higher torque is to be transferred onto the drive shaft  382 , which may amount to twice the torque, which can be transferred by one servomotor. 
     Both servomotors  292   a ,  292   b  are connected via separate feed cable connections  487 ,  488 , and the partially illustrated connection line  489 , to their respective motor control devices  484 ,  486 . One of the servomotors  292   a ,  292   b , or both motors, can be actuated and controlled via these control devices and separate electrical supplies to the motor control device  484 ,  486  and also to the servomotors  292   a ,  292   b.    
     The motor control devices  484 ,  486  are especially formed in that one of the servomotors  292   a ,  292   b  is wired as the master and the other as the slave and synchronization of both motors to the common drive of the drive shaft  382  occurs by software. 
     The electric motors  364   a ,  364   b  formed as stepper motors, are also arranged double in order to substitute one of the stepper motors with failure, damage or a similar condition. Also in this case, the control of the stepper motors  364   a ,  364   b  occurs independently of one another over dedicated feed cables  487 ,  488  and dedicated motor control devices  484 ,  486 . 
     Through the use of at least two electric motors  292   a ,  292   b , it is ensured that with the failure of one motor, the other one continues to drive the drive shaft  382  in order to move the rotating spindle  310  and the actuating element  260  appropriately in the regulating direction  482 . All other parts of the actuating device  250  are present in the usual numbers and only the number of electric motors  292  is doubled. According to the invention, a second drive shaft is also not needed on which the second electric motor acts and through which it controls the rotating spindle  310  and actuating element  260 . As a consequence, overall the actuating device  250  according to the invention is in its dimensions essentially unchanged with respect to the previously described actuating device  250 . Alternatively, both motors  292  are used simultaneously, if, for example, a higher driving force is needed. 
     If due to the failure of both stepper motors  364   a ,  364   b , a release of the second spiral spring  332  is not possible, the release of the spiral spring  332  occurs through the torsion spring  366 , which was tensed on winding up the second spiral spring  332  for the rotationally rigid connection of the guide sleeve  330  and retaining sleeve  326   a  between the clamping sleeve  499  and the ring flange  336 . 
     Otherwise the actuating device  250  according to the invention functions as follows: 
     The ball nut  306  is rotated through the rotating sleeve  496  by rotating the drive shaft  382 . Since the ball nut  306  is fixed in the axial direction relative to the housing  254 , the rotating spindle  310  is displaced in the regulating direction  482  when the ball nut  306  is rotated. The actuating element  260  is also displaced at the same time as the rotating spindle  310 , because the actuating element  260  is connected to the rotating spindle  310  via the spindle head  340 . The displacement of the actuating element  260  can be measured via the position sensor  295 . 
     In order to obtain a bearing mechanism of high quality and high efficiency which is at the same time reversible in its movement in a simple manner, the rotating sleeve  496  can be driven by a drive shaft via a transmission device  494 , the rotating sleeve  496  being rotationally rigidly connected to a ball nut  306  of a feed device  314 , whereby the rotating spindle  310  formed as a recirculating ball spindle for movement in the regulating direction is rotationally supported in the ball nut  306 . In this way the drive force of the electric motors  292  is transferred to the ball nut  306  via the rotating sleeve  496 . The ball nut  306  rotates together with the rotating sleeve  496  and with the suitable rotation the recirculating ball spindle  310  is moved in the regulating direction  482  and consequently also the actuating element  260 . It is also possible that instead of the previously described ball screw drive, a roller screw drive is analogously applied. 
     The force applied to the actuating element  260  from the direction of the control device  484 ,  486 , which is not illustrated, in the opposite direction to the regulating direction  482  is transferred via the first spiral spring  318  from the rotating sleeve  496  to the ring flange  300  and therefore to the housing  254 . 
     For resetting the actuating element  260  in the opposite direction to the regulating direction  382 , the second spiral spring  332  is released via the dog  495 , the spiral spring  332  holding the guide sleeve  330  with the retaining sleeve  326   a  rotationally rigid in the direction opposite to the feed rotational direction. With the second spiral spring  332  released, the guide sleeve  330  can rotate in the direction opposite the feed rotational direction, whereby the rotation onto the guide sleeve  330  is transferred via the guide elements  497  of the spindle head  340  corresponding to the reverse rotation of the rotating spindle  310 . 
     Referring now to  FIG. 22 , there is shown another electrical device  46 , namely an electrically-actuated injection valve  500  having isolation device  501  and an injection valve  502  as is described in U.S. patent application Ser. No. 10/415,696, filed Oct. 30, 2001 and entitled Isolating device which claims the benefit of PCT/EP01/12548 filed Oct. 30, 2001, which claims the priority of DE 200 18 562.4 filed Oct. 30, 2000 (1600-08700; OTE-030329), all of which are hereby incorporated by reference herein in their entirety. The isolation device  501  comprises a device housing  503  constructed of various interconnected sub-housings  547 ,  548 ,  549  and  550 . Sub-housing  547  encloses a drive device  505  including two electric motors  509  and  510  arranged at both ends of a worm shaft  519  on which a worm  517  is provided. Sub-housing  547  may also comprise an emergency release device  526  that can be actuated by another electric motor  532 . Connection  514  and a connecting line  186  connects motors  509  and  510  with remotely arranged control devices  512  and  513  or controller  112 . The electric motors  509 ,  510 ,  532  may be powered by either DC or AC voltage, preferably DC voltage. 
     Referring now to  FIG. 23 , a section along the line II-II of  FIG. 22  is shown, including the injection valve  502  with a corresponding injection valve housing  561 . Injection valve  502  is attached to isolating device  501  by threaded sleeve  580  and comprises a connection line  562  providing fluid communication between a fluid pump  563  and a ball valve of valve arrangement  564 . An isolation stop valve  507  engages the connection line  562 , such that the connection between the pump  563  and the valve arrangement  564  is interrupted. Shifting the isolation stop valve  507  out of the isolating device  501  moves slider opening  585  of the isolation stop valve  507  into connection line  562  and allows fluid communication through the connection line  562 . 
     The isolation stop valve  507  is arranged at the end of an operating element  506  that is arranged within a piston housing  571  and connected to a shaft section  572 . The piston housing  571  comprises a radially extending end flange  576  that supports one end  577  of a spring arrangement  565 . Spring arrangement  565  urges operating element  506  into a starting position  574 , in which the end flange  576  is adjacent to a locknut  573  screwed into the sub-housing  549 . 
     Sub-housing  549  is connected to sub-housing  548 , which encloses a screw  539 . Screw  539  is formed of a screw nut  540 , in this case a revolving roller nut, and the turning spindle  504 , forming together a planetary roller screw. At its end  569  facing the operating element  506 , the turning spindle  504  is inserted into a hole at the end  570  of the operating element  506  or the shaft section  572 , respectively, and held therein by means of a bolt. The screw nut  540  is rotatable, but axially fixed within bearing sleeve  542 . 
     Opposite to the end  569 , the turning spindle  504  projects with its other end  543  from the screw nut  540  and is there also surrounded by a section of the lower-diameter bearing sleeve  542 . At the outside of this section, the bearing sleeve  542  is rotatably mounted to sub-housing  548  by needle bearing  544 . A bearing shaft  535  passes through the bearing sleeve  542 , the end  568  thereof being inserted in the end  543  of the turning spindle  504  and being stationarily held therein. In  FIG. 23 , the turning spindle  504  is represented in its starting position  566 , i.e. as far as possible inserted through the screw nut  540  in the direction away from the injection valve  502 . 
     The bearing shaft  535  is arranged in a bearing sleeve  536 , which is connected to a worm wheel  518  via a spline connection. The worm wheel  518  is a globoid worm wheel and engaged with worm  517 . The bearing sleeve  536  is rotatably mounted in the sub-housing  547  via needle bearings  544 . The end of the sub-housing  547  that is opposite to the sub-housing  548  is detachably sealed by an end plate  559 . Sub-housing  550  is detachably connected to end plate  559  and encloses positioning sensor  295 . End plate  559  also includes electrical passages  567  to provide electrical connection between connection  514  and devices within sub-housing  547 . A connecting line  186  connects the subsea power source  102  to electrically-actuated injection valve  500 . 
     Referring now to  FIG. 24 , a section along the line III-III of  FIGS. 22 and 23 , respectively, is represented. The sub-housing  547  is essentially formed of a central body  553  in which a central bore  554  is formed. In this bore, the bearing sleeve  536  of  FIG. 23  is rotatably mounted. The worm wheel  518  is stationarily connected to the bearing sleeve  536  via the splined shaft connection  537  in the form of a ratchet. The same is engaged with its external gearing in a corresponding external gearing of the worm  517 . The worm  517  is arranged on a worm shaft  519 , which extends approximately tangentially to the central bore  554 . 
     Shaft ends  520 ,  521  of the worm shaft  519  are rotatably mounted by means of a ball bearing  533  or a roller bearing  534 , respectively. An electric motor  509 ,  510  of the drive device  505  is associated to each of the ends  520 ,  521  of the worm shaft  519 . The electric motor  509  is directly actively connected with the shaft end  520  or a motor shaft  522 , respectively, and is detachably mounted in motor opening  555  in the central body  553 . The other electric motor  505  is also detachably held in a motor opening  556 . A synchronous operation of both electric motors  505 ,  509  can be effected with software with at least one electric motor as master and the other electric motor as slave to provide high torque and high rotational speeds that can be transmitted by the corresponding gearbox unit. 
     One end  525  of the motor shaft  522  extends beyond the electric motor  509  along a narrowed section of the supporting sleeve  527 . The motor shaft  522  extends beyond the supporting sleeve  527  into a spacing sleeve  528  that is connected to the supporting sleeve  527  via a volute spring  529  that limits the rotation of the spacing sleeve relative to the supporting sleeve to one direction. With one of its ends  530 , the volute spring  529  engages a release sleeve  531 , which is rotatably mounted with respect to the spacing sleeve  528  and the supporting sleeve  527 . The release sleeve  531  is actively connected to a drive shaft of a stepper motor  532  that is arranged in a side housing  596  in the extension of the motor opening  555 . The side housing  596  is detachably sealed by a cover  582 . 
     Referring now to  FIG. 25 , there is shown another electrical device  46 , namely a longitudinal section through a specific embodiment of a valve system  601  as described in U.S. patent application Ser. No. 10/467,112 filed Oct. 30, 2001 and entitled Valve System, which claims the benefit of PCT/EP01/12550 filed Oct. 30, 2001, which claims priority from DE 20012168.4, filed Feb. 8, 2001 (1600-08900; OTE-030331), all of which are hereby incorporated by reference herein in their entirety. Valve system  601  comprises a valve body  602  and a longitudinal slide  603  disposed within a valve holding recess  616  of a valve block  615 . An electrochemical actuator  609  is associated with longitudinal slide  603  of the valve system  601 . 
     Electrochemical actuator  609  has a gas generator  662 , that generates a gas, and, in particular, hydrogen, when an electric charge is supplied via corresponding feed lines. The electric charge is supplied by connecting lines to subsea voltage source  102 . The electric supply may be either DC or AC voltage, preferably DC voltage. The generated gas generates an over-pressure in the interior of the gas generator  662  and a discharge element  658  of the actuator may be displaced in the direction of the valve block  615  via this over-pressure. The discharge element  658  is connected with the gas generator  662  via a bellows element  661 . 
     The discharge element  658  is releasably connected with a holding plate  657  at the end of the discharge element turned away from the gas generator  662 . The longitudinal slide  603  is releasably attached to the middle of the holding plate  657  and is movably mounted in the housing cover  619 . A connecting end  613  of the longitudinal slide  603  projects into the interior  620  of the housing  617  and there is attached to the holding plate  657 . The longitudinal slide  603  extends from its connecting end  613  up to its inlet end  614  that is associated with the feed line  604  in a bottom of the valve holding recess  616 . 
     Valve block  615  has inlet channels  624 ,  625  and outlet channels  626 ,  627 . Fluid communication between longitudinal bore  610  and inlet channels  624 ,  625  and outlet channels  626 ,  627  is controlled by the linear position of longitudinal slide  603 . In  FIG. 25  the longitudinal slide  603  is shown in its outlet position, in which the feed line  604  is in fluid communication with outlet channels  626 ,  627  via longitudinal bore  610  and connecting lines  611 ,  612  of slide  603  and channels  631 ,  632  of central body  628 . 
     The longitudinal slide  603  is moved to a fluid feed position  653  (see the dashed line representation in  FIG. 25 ) by the electrochemical actuator  609 . In the fluid feed position  653 , connecting lines  611  and  612  of longitudinal slide  603  align with annular channel  646  of throttle element  637 . Throttle element  637  comprises a throttle component  638  having a middle bore  639  and a guide body  640 . Throttle element  637  provide fluid communication between feed line  604  and inlet channels  625 ,  626  via connecting lines  611 ,  612 . 
     Hydrogen is generated in the electrochemical actuator  609  by means of an electric charge. The discharge element  658  is discharged with the holding plate  657  in the direction of the feed line  604  by means of the corresponding over-pressure. Analogously, there is a displacement of the longitudinal slide  603  into the fluid feed position  653 . A connection is made in the latter between feed line  604  via longitudinal bore  610  and connecting line  611 ,  612  to the inlets  605 ,  606  and via the latter to the inlet channels  624 ,  625 . Hydraulic fluid is fed to the actuation device in this fluid feed position  653 . 
     Referring now to  FIG. 26 , another electric device  46  is shown, namely a longitudinal sectional view through a rotary adjusting device  701  as described in U.S. patent application Ser. No. 10/415,511, filed Oct. 30, 2001 and entitled Rotating Regulating Device which claims the benefit of PCT/EP01/12554 filed Oct. 30, 2001, which claims the benefit of DE 200 18 548.9 filed Oct. 30, 2000 (1600-08300; OTE-030332), all of which are hereby incorporated by reference herein in their entirety. The rotary adjusting device  701  is designed as an installed module  707  and flange mounted to an actuator device  725 . Actuator device  725  comprises at least one electromotor  743  that drives a ball screw  744 , with a ball nut  746  that can be turned by the electromotor  743 . Turning the ball nut  746  causes a recirculating ball spindle  745  of the ball screw  744  to be repositioned in the longitudinal direction of the actuator device  725 . An operating element  724  which is connected to the recirculating ball spindle  745  is repositioned accordingly, and thus likewise a feed element  722  of the rotary adjusting device  701 . The electric motor  743  may be powered by either DC or AC voltage, preferably DC voltage. A connecting line  186  may extend to connector  709 , which is connected to motor  743 . 
     The feed element  722  is mounted in a longitudinal bore  723  of a rotary sleeve  704  of the rotary adjusting device  701  in such a way that it can be shifted. The rotary sleeve  704  is rotatably mounted in the interior of a bearing sleeve  705  that is removably attached to the actuator device  725 . The rotary sleeve  704  is mounted so that it can rotate but cannot shift axially relative to the bearing sleeve  705 . 
     To translate the linear motion of the operating element  724  into a rotary motion of the rotary sleeve  704  relative to the bearing sleeve  705 , a transmission  706  is positioned between the two as an activating device  702 . The transmission  706  comprises the feed element  722 , a meshing pin  717  as meshing element  716 , ball or roller bearings  720 , and guide slots  711 ,  712  in the rotary sleeve  704  as well as guide slots  713 ,  714  in the bearing sleeve  705 . 
     As shown in  FIG. 27 , guide slots  713 ,  714  of the bearing sleeve  705  run in a straight line in the longitudinal direction  715 , whereas the guide slots  711 ,  712  in the bearing sleeve  705  run diagonally to the longitudinal direction  715  and in particular in a spiral pattern. The meshing pin  717  engages longitudinal slots  739 ,  740  of a spring bearing sleeve  734  with its outermost ends  735 ,  736 . These longitudinal slots are open in the direction of the ring flange  726  of the bearing sleeve  705 . In the area of the ring flange  726  the spring bearing sleeve  734  also has a terminating flange  737 , which is in contact with the ring flange  726  when the spring bearing sleeve  734  is in the end position  738  shown in  FIG. 26 . Between the terminating flange  737  and the ring flange  730  of the closing ring  729  there is a compression spring as spring element  733 . This applies pressure to the activating device  702  of the rotary adjusting device  701  counter to the adjustment direction of the operating element  724 . 
     Moving the feed element  722  in the direction of the closing ring  729  by means of the operating element  724  of the actuator device  725  causes the meshing pin  717 , as the meshing element  716 , to move along the guide slots  711 ,  724  to their ends which are toward the closing ring  729 . At the same time the meshing pin  717  moves along the linear guide slots  713 ,  714  of the bearing sleeve  705 , which is firmly connected to the actuator device  725 . Because of the spiral form of the other guide slots  711 ,  712  of the rotary sleeve  704 , when the meshing pin  717  is moved along the guide slots  713 ,  714  and because the meshing pin  717  at the same time engages the guide slots  711 ,  712 , the rotary sleeve  704  is rotated by a corresponding angle. The angle of rotation then comes from the oblique path of the guide slots  711 ,  712  relative to the guide slots  713 ,  714 . 
     To support a return of the adjusting element  703  into the end position of the spring bearing sleeve  734  shown in  FIGS. 25 and 27 , there is a compression spring  733  between the ring flange  730  of the closing ring  729  and the terminating flange  737  of the spring bearing sleeve  734 . The spring bearing sleeve  734  is carried along when the meshing pin  717  is moved in the direction of the closing ring  729 ; the ends  735 ,  736  of the meshing pin are in contact with ends  741 ,  742  of the longitudinal slots  739 ,  740  which are formed in the spring bearing sleeve  734 . 
     Referring now to  FIG. 28 , there is shown another electrical device  46  namely an actuating device  801  in accordance with U.S. patent application Ser. No. 10/415,418, filed Sep. 4, 2003 and entitled Actuating Device, which claims the benefit of PCT/EP01/12549 filed Oct. 30, 2001, which claims the priority of DE 200 18 563.2 filed Oct. 30, 2000 (1600-08800; OTE-030328), all of which are hereby incorporated by reference herein in their entirety. Actuating device  801  is shown enclosed in a device housing  803  that is connected to a throttle device  802  including a throttle housing  851  having a fluid inlet  859  and fluid outlet  860 . Electrical connector  813  connects actuating device  801  to the remotely disposed control and actuation assembly  80  by means of electrical connecting lines  186  for supplying power to electric motors  508 ,  509  powered by either DC or AC voltage, preferably DC voltage. 
     Throttle device  802  further comprises a throttle space  858  that is located between the fluid inlet  859  and the fluid outlet  860  and contains a passage sleeve  863  having a number of passage openings  885  therethrough. Opposite the fluid outlet  860  extends a throttle element bore  857  in the throttle housing  851 , in which a throttle element  862  is mounted so as to be displaceable in an axial direction. Throttle element  862  includes throttle sleeve  864  that is axially disposable between a position covering passage opening  885  and a position not covering passage openings, so as to control the flow of fluid between fluid inlet  859  and fluid outlet  860 . The axial displacement of throttle element  862  is controlled by actuating element  806 . 
     Actuating element  806  is connected to a turning spindle  804  that is displaced by rotating a thread nut  825  in which the turning spindle is rotatably mounted as recirculating ball screw or recirculating roller spindle. The turning spindle  804  and the thread nut  825  (ball nut or roller nut) form a part of a transmission device  807 , via which the actuating element  806  is functionally connected for adjustment purposes. 
     The thread nut  825  is held in a bearing sleeve  826  in manner secured against rotation and is rotatable via the axial bearing  829 . At one end  827  of the thread nut  825  facing the actuating element  806 , an outer toothing  828  is arranged, which is formed by a worm gear  817  forms part of a worm gear pair  815  and engages with its toothing  828  a corresponding outer toothing of a worm  816  as additional part of the worm gear pair  815  (also see  FIG. 29 ). 
     The worm gear  817  in the exemplary embodiment according to the invention is formed by a globoid worm wheel, the outer toothing of which is engaged by a corresponding outer toothing of a cylindrical worm  816 . The worm  816  is arranged as an additional part of the worm gear pair  815  on a worm shaft  818 . The worm  816  and the worm gear  817  form a transmission unit  810  as part of the transmission device  807  whereby such transmission unit  810  forms a self-locking transmission unit. By means of its two shaft ends  819 ,  820  the worm shaft  818  is releasably connected with electric motors  808 ,  809  forming a drive device  805  of the actuating device  801 . The electric motors  808 ,  809  are servomotors, especially direct current servomotors. 
     Thus, the actuating device  801  comprises an electric drive device formed by two servomotors  808 ,  809 . Such servomotors  808 ,  809  are remotely controllable via corresponding connecting lines and their control devices  811 ,  812 . When actuating one motor or both motors in synchronous operation, such motors drive the worm shaft  818  and thus the worm  816 . Such worm  816  is engaged with the appertaining worm gear  817 . The worm and the worm gear form a self-locking worm gear pair being locked at least oppositely to the feed direction of the turning spindle  804  in the direction of the throttle device. The self-locking state of the worm gear pair can only be released by applying a release torque from the servomotors  808 ,  809 . 
     Especially in interaction with the roller thread as additional part of the transmission device  807 , the worm gear pair easily results in a high gearing and allows the transmission of a high torque. The gearing can be selected, according to desire, by correspondingly selecting the worm, worm gear, thread nut and turning spindle. When the thread nut  825  directly connected with the worm gear in a manner secured against rotation is rotated, the turning spindle  804  is correspondingly extended in the direction of the actuating device or is retracted in the opposite direction. Connected with the turning spindle  804  is the actuating element  806  at the free end of which a corresponding throttle element is disposed. The actuating element with the throttle element engage the throttle housing adjacent to the actuating device  801 , where they serve to vary the fluid passage between the fluid inlet and the fluid outlet. 
     Referring now to  FIG. 30 , there is shown still another electrical device  46  namely an actuating device for a subsea valve in accordance with German patent application No. DE 203 11 033 filed Jul. 17, 2003 and entitled Pump Device, hereby incorporated herein by reference. In  FIG. 30  a longitudinal section through one embodiment of an inventive pump device  901  is illustrated. Pump device  901  includes electrically operated driving device  905 , which is made up of a rotatable but axially non-movable mounted spindle nut  910  and an axially movable, but non-rotating threaded spindle  911 . Spindle nut  010  is fixed to rotary socket  915  that is rotatably mounted inside a pump housing  935  by means of a set of angular roller bearings. 
     The rotary socket  915  is connected to a harmonic transmission  913  that is driven by gear  919 . Gear  919  engages gear  920  that is rigidly arranged on a drive shaft  921  that is turned by two electric motors  909  in the form of a synchronous or asynchronous motors. The electric motors  909  may be powered by either DC or AC voltage, preferably DC voltage. Operating motors  909  turn gear  920 , which engages and rotates gear  919  and rotary socket  915  through harmonic transmission  913 . The rotation of rotary socket  915  also rotates spindle nut  910 , which causes axial translation of threaded spindle  911 . Position sensor  295  may monitor the axial position of threaded spindle  911 . A connector  907  connects the electric motors  909  with connecting lines  186  extending to a subsea power source  102 . 
     The threaded spindle  911  is detachably connected to piston  961 , which is mounted so as to be able to move axially within piston space  923  of piston cylinder unit  903 . Piston space  923  has a cylinder base plate  930 , in which an intake hole  926  and a discharge hole  927  are formed substantially parallel to one another. A non-return valve  928 , which is spring-biased in the direction of the intake hole  926  is arranged on the side of the piston space  923  in front of the intake hole  926 , similarly a non-return valve  929  which is spring-biased in the direction of the piston  961  is arranged on the side of the piston space  923  in front of the discharge hole  927 . 
     If piston  961  moves to the left, the non-return valve  928  is opened by corresponding negative pressure in the piston space  923  and hydraulic fluid  904  enters the piston space  923  through the intake hole  926 . If piston  961  moves to the right, the hydraulic fluid present in the piston space  923  is forced through the open non-return valve  929  into the discharge hole  927 . 
     The intake hole  926  leads to a buffer tank  931 , which substantially surrounds the cylinder base plate  930  and serves to store hydraulic fluid, which can be fed through a supply line  933 . The supply line  933  may be connected to a hydraulic fluid supply line  958  by a snap-coupling mechanism  957 . This snap-coupling mechanism  957  likewise serves to connect a discharge pipe  934 , which extends from the discharge hole  927  through the buffer tank  931 , and which is then led further in the direction of the valve  902 . 
     The discharge pipe  934  has at least one branch feeder pipe  936  on its section running between the snap-coupling mechanism  957  and the valve  902 , to which an accumulator  937  as pressure storage means for hydraulic fluid is attached. In the case of one embodiment this accumulator contains a number of Belleville springs  938 , which are stacked in parallel and/or in series. The accumulator  937  works as pressure storage means due to the arrangement of the Belleville springs  938 . By suitable dimensioning of the accumulator, valve and actual pump this can operate maintenance-free over a long period whereby due to the provision of the accumulator the pump can be intermittently operated. 
     As an example, assume a required pressure of approximately one kbar for valve  902 . Pump device  901  is operable to generate a fluid pressure of 1.4 kbar. Therefore, accumulator  937  maintains hydraulic fluid at approximately 1.4 kbar. Thus, pump device  901  does not need to be operated until the pressure loss in the accumulator amounts to more than approximately 0.4 kbar. Only when the pressure drops to a value of less than 1.0 kbar will the pump begin to work again and recharge the accumulator. 
     In some embodiments, a safety relief valve  942  e.g., a subsurface safety valve, is provided to prevent pressure within pump device  901  from exceeding a pre-set limit. In the vicinity of the buffer tank  931  and/or the cylinder base plate  930  a first branch pipe  939  and a second branch pipe  940  branch off from the discharge pipe  934  and/or the discharge hole  927 . The first branch pipe  939  extends as far as a pressure switch  941 , which, depending on the pressure of the hydraulic fluid, transmits an electrical signal to an actuator  944 . Actuator  944 , as for example a step motor, has a drive shaft, at one end of which a pinion  945  is arranged, that engages with a cam disk  946 , which is rotatably mounted by means of roller bearings  965  on an outer periphery  956  of the rotary socket  915 . The cam disk  946  has gearing assigned to the pinion  945  as well as at least one control cam  948  with a control tappet  947  of a safety relief valve  942 . 
     The safety relief valve  942  is designed as mechanically controllable non-return valve  943 . Safety relief valve  942  is opened by control tappet  947  if roller  950  runs onto the control cam  948 . Opening valve  942  allows fluid communication between second branch pipe  940  and return line  955 , which leads to buffer tank  931 . As a result no discharge to the environment takes place and equally there is no corresponding contamination or also feedback to a far away place as for example from the sea bed to the sea surface. 
     A reverse rotation device  952 , such as a clockwork-similar coil or spiral spring  953 , is assigned to the actuator  944 . The reverse rotation device  952  is arranged such that in the event of failure of the actuator  944  and with the safety valve  942  open, the cam disk  946  is automatically turned back by the tension of the coil/spiral spring so that closure of the safety valve  942  is ensured both by the spring-bias of the valve element in the direction of the closed position and also in particular by the reverse torque of the coil/spiral spring as reverse rotation device  952 . 
     Referring now to  FIG. 31 , there is shown another embodiment of the present invention. An electrically controlled subsea production system  1000  includes a surface platform  1010  and one or more subsea trees  1020 . Surface platform  1010  corresponds to the first location  42  as shown and described in reference to  FIG. 1( c )  and subsea trees  1020  correspond to the remote location  50  as shown and described in reference to  FIG. 1( c ) . Subsea trees  1020  include electric control pods  1080  connected via electrical conductors  1050  from a subsea electrical distribution skid  1030  that is electrically coupled to surface platform  1010  via electrical control umbilical  1040 , e.g., umbilical  68 . Subsea trees  1020  also include production outlets  1090  that send production fluids through conduits  1060  and production riser  1070  to surface platform  1010 . Subsea trees  1020  are preferably operated with only electrical control inputs from surface platform  1010  operating electrical devices  46 , such as actuators, on the trees but may also include hydraulic and electro-hydraulic control systems when desired. 
     Referring now to  FIG. 32 , a schematic representation of some of the surface mounted components of production system  1000  are shown. Master control station  1100  includes a channel A  1102  and channel B  1104 , each generated by a surface communication control unit  1106 ,  1108 , respectively. Master control station  1100  communicates through connections  1110  and  1112 , e.g. controller  76 , with the platform control system and through hardwired and optically isolated interfaces with a high voltage converter  1120 , e.g., converter  72 . High voltage converter  1120  draws dual three-phase electrical power from platform uninterruptible power supply  1114 , e.g.,  78 , and supplies isolated DC supply power to at least four conductors  1122 ,  1124 ,  1126 , and  1128  within an electrical umbilical  1040 , e.g., umbilical  68 . Umbilical  1040  is connected to a mechanical hang off  1132  disposed on platform  1010 . 
     Electrical umbilical  1040  carries electrical power and communication from platform  1010  to electrical distribution skid  1030 . Umbilical  1040  may comprise at least eight high voltage coaxial cables that are manufactured in one continuous length. 
     Referring now to  FIG. 33 , umbilical  1040  terminates in connector  1236  that interfaces with electrical umbilical termination  1238 . Electrical umbilical termination  1238  includes a plurality of pig-tail conductors  1240  that connect each of the electrical conductors in umbilical  1040  with electrical distribution skid  1030 . 
     Electrical distribution skid  1030  comprises a plurality of high voltage converters (bullnoses)  1250 , e.g., converter  86  with converter components  122 , to convert the high voltage (3,000 to 6,000 VDC) supply from the surface down to 300 VDC to power subsea trees  1020  and to decouple the communications from the DC power. Bullnoses  1250  are preferably a modular construction sized to accommodate sufficient electronic units to step down the power and work to precisely control the voltage supplied to the subsea trees  1020  by diverting surplus power. A bullnose  1250  is provided for each electrical conduit from umbilical  1040 . Mounting bases  1252  for additional bullnoses may also be provided for expansion. 
     Pig-tail conductors  1240  provide inputs to bullnoses  1250 , which convert the high voltage from umbilical  1040  to lower voltage current. This lower voltage current is then passed along electrical jumpers  1254  to electric control pods  1080  mounted on subsea trees  1020 . Electrical jumpers  1254  from the electrical distribution skid  1030  carry the 300 VDC supply for the subsea trees  1020  and a screened communications cable to provide instructions to control pods  1080 . The ends of each electrical jumper  1254  are terminated with a multi-pin ROV wet mate connector. 
     Electric control pods  1080  serve two functions. Firstly, it controls the various functions on the subsea tree, and secondly, it acquires data from the tree and the subsea instrumentation for transmission to the surface. Control pods  1080  are preferably lightweight units of a universal design and are configured to serve the functional requirements of subsea trees  1020 . Control pods  1080  are preferably tree mounted and can be installed and retrieved using standard ROV&#39;s or remotely operated running tool. Electrical connections between the control pods  1080  and subsea trees  1020  are made remotely using wet-mate electrical connectors through a pod mounting base. 
     A subsea electronic module is housed within each control pod  1080 , e.g. controller  112 , and is used to effect all electronic communication and to monitor internal and external pod field sensors. The subsea electronic module also controls the operation of the actuated valves on subsea tree  1020  upon receipt of a command signal from master control station  1100  (see  FIG. 32 ). 
       FIG. 34  shows a schematic view of a subsea tree assembly  1020  including a tree  1310  landed on wellhead connector  1300  of subsea wellhead  1302 . The tree may be a spool tree, dual bore tree or other type of tree having subsea devices. Tree  1310  is a spool tree. A sealing sleeve  1304  is shown extending between wellhead  1302  and a counterbore in the lower end of the tree  1310 . Tubing hanger  1306  is supported within tree  1310  and has a lateral production port  1308  aligned with a lateral production port  1312  in tree  1310 , the flow through which is controlled by production master valve  1314 . An external flow line  1316  is shown extending from production master valve  1314  to a production wing valve  1318  and a production choke valve  1320 . Line  1322  extends from flow line  1316  and connects to a production isolation valve  1324  and a test isolation valve  1326 . Flow through flow line  1316  connects to production outlets  1090  (see  FIG. 31 ). 
     The tubing hanger  1306  suspends tubing  1328  down through wellhead  1302  and into the cased borehole. A surface controlled subsea safety valve  1330  and a downhole pressure and temperature transducer  1332  are disposed in the lower end of production tubing  1328 . A control line  1334  extends through the spool tree  1310  and out the side of tubing hanger  1306  to control the downhole safety valve  1330 . Likewise, an electrical line  1336  extends downhole to the pressure and temperature transducer  1332  to transmit signals from the transducer. The downhole safety valve  1330  is preferably electrically controlled as previously described. 
     An annulus passageway  1338  extends from the production tubing annulus and into a annulus passageway  1342  in the body of spool tree  1310 . An annulus master valve  1344  controls flow through annulus passageway  1342 . Workover passageway  1346  communicates with the annulus passageway  1342  and extends upwardly through the wall of spool tree  1310  to an opening in the interior wall of the spool tree  1310  to provide communication with the spool tree bore  1348  above tubing hanger  1306 . A workover valve  1350  controls flow through the workover passageway  1346 . A cross over line  1352  communicates between passageway  1354  flow line  1316 . A cross over valve  1356  controls the flow therethrough. An annulus wing valve  1358  and a gas lift choke valve  1360  are disposed in passageway  1354 . 
     In the preferred embodiments, each of the valves used in subsea tree assembly  1020  utilize electrical actuators that are powered and controlled by master control station  1100  via electrical umbilical  1040  and electric control pods  1080 . The motors used by the electrical devices  46  are preferably powered by DC voltage. By eliminating hydraulically actuated valves, control and operation of subsea tree assembly  1020  is all electrically controlled. In summary, the electric system offers many advantages, such as quick response, elimination of hydraulic fluid, no dumping of fluid to sea (environmentally friendly), and the ability to perform real time diagnostics on the actuators, valves, and chokes. At the surface, the requirement for a hydraulic power unit is eliminated and the surface equipment can be packaged more compactly. 
     It is preferred that the subsea wellhead assembly include a subsea tree having all electrically actuated actuators. It is further preferred that the electrically actuated actuators have DC motors whereby the subsea DC voltage source supplies DC voltage to the DC motors. The subsea DC voltage source receives a high DC voltage from a voltage supply and control assembly at the surface via an umbilical and a plurality of subsea voltage converters convert the high DC voltage to a low DC voltage for supplying the electrically actuated actuators. Preferably all actuators disposed on the tree are electrically actuated actuators. 
     The embodiments set forth herein are merely illustrative and do not limit the scope of the invention or the details therein. It will be appreciated that many other modifications and improvements to the disclosure herein may be made without departing from the scope of the invention or the inventive concepts herein disclosed. Because many varying and different embodiments may be made within the scope of the present inventive concept, including equivalent structures or materials hereafter thought of, and because many modifications may be made in the embodiments herein detailed in accordance with the descriptive requirements of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense.