Patent Publication Number: US-7724489-B2

Title: Circuit breaker with high speed mechanically-interlocked grounding switch

Description:
CROSS-REFERENCE TO RELATED U.S. APPLICATIONS 
   Not applicable. 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not applicable. 
   NAMES OF PARTIES TO A JOINT RESEARCH AGREEMENT 
   Not applicable. 
   REFERENCE TO AN APPENDIX SUBMITTED ON COMPACT DISC 
   Not applicable. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to vacuum circuit breakers. More particularly, the present invention relates to circuit breakers having a mechanically interlocked grounding switch. Additionally, the present invention relates to circuit breakers for use in association with wind farm collection circuits. 
   2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98. 
   Wind farms are becoming increasing popular for the generation of electricity. In a wind farm, there are a large number of wind energy generators installed in locations of the country where wind is consistent and substantial. Typically, the wind energy generators will include an array of blades that are coupled to a shaft. The rotation of the shaft caused by the rotation of the blades will produce electrical energy. Electrical lines will connect with the energy generator so as to deliver the energy from a particular wind energy generator to a collection bus. The electrical energy from the various wind energy generators in the wind farm can collectively pass energy to a substation. 
   Typically, these wind turbines can each produce between 500 kW and 3500 kW of power. The outputs of generators in the wind farm are often grouped into several electrical collection circuits. Transformers are used so as to tie the wind turbine output the conductors to the 34.5 kV collection circuits. The transformers serve to step up the output voltage of the wind energy generators to a medium voltage, usually 34.5 kilovolts. The various wind turbines in a wind farm are usually paralleled into collection circuits that can deliver 15 to 30 megawatts of power. In view of the voltage which has been stepped up to the 34.5 kilovolts, each collection circuit will require a circuit breaker rated at a minimum 34.5 kilovolts capacity. The energy will pass through the circuit breaker to the 34.5 kV bus of a substation. The 34.5 kV substation bus will go into one or more main step-up transformers and then tie into a high voltage utility line. As such, a need has developed so as to provide a circuit breaker that can tie collection circuits into the 34.5 kV substation bus. Such a circuit breaker should be of low cost, weatherproof, and able to effectively break the current in the event of a problem condition. 
   Typically, with circuit breakers, the circuit to the substation can be broken upon the application of a manual force to a button or lever of the circuit breaker or by an automatic relay which opens the circuit. Typically, the current is measured to the substation. If any relay senses a problem, then a signal is transmitted to the circuit breaker so as to open the breaker. Typically, the relays will be maintained within the substation. The opening of the circuit breaker will prevent the energy from being continued to be transmitted to the substation. Sometimes, the circuit breaker is open so as to allow users to work on the wind farm system, on the circuit breaker, or on the substation. Typically, the relays will operate if the sensors sense a voltage drop. 
   The interruption of electrical power circuits has always been an essential function, especially in cases of overloads or short circuits, when immediate interruption of the current flow becomes necessary as a protective measure. In earliest times, circuits could be broken only by separation of contacts in air followed by drawing the resulting electric arc out to such a length that it can no longer be maintained. This means of interruption soon became inadequate and special devices, termed “circuit breakers”, were developed. The basic problem is to control and quench the high power arc. This necessarily occurs at the separating contacts of a breaker when opening high current circuits. Since arcs generate a great deal of heat energy which is often destructive to the breaker&#39;s contacts, it is necessary to limit the duration of the arc and to develop contacts that can withstand the effect of the arc time after time. 
   A vacuum circuit breaker uses the rapid dielectric recovery and high dielectric strength of the vacuum. The pair of contacts are hermetically sealed in the vacuum envelope. An actuating motion is transmitted through bellows to the movable contact. When the electrodes are parted, an arc is produced and supported by metallic vapor boiled from the electrodes. Vapor particles expand into the vacuum and condense on solid surfaces. At a natural current zero the vapor particles disappear and the arc is extinguished. 
   In the past, various patents have issued relating to such vacuum circuit breakers. For example, U.S. Pat. No. 5,612,523, issued on Mar. 18, 1997 to Hakamata et al., teaches a vacuum circuit-breaker and electrode assembly. A portion of a highly conductive metal member is infiltrated in voids of a porous high melting point metal member. Both of the metal members are integrally joined to each other. An arc electrode portion is formed of a high melting point area in which the highly conductive metal is infiltrated in voids of the high melting point metal member. A coil electrode portion is formed by hollowing out the interior of a highly conductive metal area composed only of the highly conductive metal and by forming slits thereon. A rod is brazed on the rear surface of the coil electrode portion. 
   U.S. Pat. No. 6,048,216, issued on Apr. 11, 2000 to Komuro, describes a vacuum circuit breaker having a fixed electrode and a movable electrode. An arc electrode support member serves to support the arc electrode. A coil electrode is contiguous to the arc electrode support member. This vacuum circuit breaker is a highly reliable electrode of high strength which will undergoes little change with the lapse of time. 
   U.S. Pat. No. 6,759,617, issued on Jul. 6, 2004 to S. J. Yoon, describes a vacuum circuit breaker having a plurality of switching mechanisms with movable contacts and stationary contacts for connecting/breaking an electrical circuit between an electric source and an electric load. The actuator unit includes at least one rotary shaft for providing the movable contacts with dynamic power so as to move to positions contacting the stationary contacts or positions separating from the stationary contacts. A supporting frame fixes and supports the switching mechanism units and the actuator unit. A transfer link unit is used to transfer the rotating movement of the rotary shaft to a plurality of vertical movements. 
   U.S. Pat. No. 7,223,923, issued on May 28, 2007 to Kobayashi et al., provides a vacuum switchgear. This vacuum switchgear includes an electro-conductive outer vacuum container and a plurality of inner containers disposed in the outer vacuum container. The inner containers and the outer container are electrically isolated from each other. One of the inner vacuum containers accommodates a ground switch for keeping the circuit open while the switchgear is opened. A movable electrode is connected to an operating mechanism and a fixed electrode connected to a fixed electrode rod. Another inner vacuum container accommodates a function switch capable of having at least one of the functions of a circuit breaker, a disconnector and a load switch. 
   In the past, in association with such wind farms, when collect circuit breakers are opened, the collection circuit voltage would be interrupted and a transient overvoltage situation could occur in the collection circuit. In the over voltage situation, the high transient voltage in the collection circuit line will “back up” through the circuit and to the electronics associated with the wind energy generators. As a result, this transient overvoltage could cause damage to the circuitry associated with the wind energy generators and other circuitry throughout the system. As a result, in view of the characteristics of the large energy resident within by the overall wind energy farm, there is an extreme need to hold within acceptable limits any overvoltage which occurs when the circuit breaker is be opened. 
   Typically, to avoid the over voltage situation, grounding transformers have been required to be installed. These grounding transformers would typically have 34.5 kilovolts on the primary winding with a 600 volts open delta secondary winding. The transformer has a core with windings therearound. In view of the core and windings, there was continuous amount of core losses of energy associated with the use of such grounding transformers. Over time, the core losses could amount to a significant dollar amount of lost energy. Additionally, these grounding transformers had a relatively high initial cost, installation cost, and a long lead time of delivery. 
     FIG. 1  is an illustration of a prior art system employing a ground transformer. As can be seen, wind power generators  10 ,  12 ,  14  and  16  are connected respective lines  18 ,  20 ,  22  and  24  to a bus  26  via step-up transformers  17 ,  19 ,  21  and  23 . The bus  26  has a switch  28  located therealong. The grounding transformer  30  is connected forwardly of the switch  28 . When the switch  28  is opened, as illustrated in  FIG. 1 , the energy along the bus  26  is passed to the ground transformer  30  and to ground. When the switch  28  is closed, the energy from the bus  26  is passed along another bus  32  for passage to the circuit breaker  34  and then along line  36  to the substation  38 . When the ground transformer  30  is effectively used, then any over voltages are immediately transferred to ground in an acceptable manner. As can be seen in  FIG. 1 , when the circuit breaker  34  is activated so as to open the circuit, a signal can be passed along line  40  to the switch  28  so as to open the switch  28  and to cause the energy in the bus  26  to pass to the ground transformer  30 . 
   When ground transformers are not used, it is necessary to switch the circuit to ground extremely quickly. If the switch does not occur within a maximum of three cycles, then the overvoltage condition can occur. Ideally, to avoid any potential for an overvoltage situation, it is necessary to close the circuit to ground within one cycle, i.e. 16 milliseconds. Ultimately, experiments in attempting to achieve electrical switching systems indicated that the switching would occur at a level dangerously close to the five cycle limit. Preferably, it is desirable to cause the switching to occur in as close to an instantaneous manner as possible. 
   It is an object of the present invention to provide a vacuum circuit breaker with an integral high speed grounding switch of a relatively low cost. 
   It is another object of the present invention to provide a vacuum circuit breaker with an integral high speed grounding switch that is weatherproof. 
   It is a further object of the present invention to provide a vacuum circuit breaker with an integral high speed grounding switch which eliminates the need for ground transformers. 
   It is a further object of the present invention to provide a vacuum circuit breaker with an integral high speed grounding switch which minimizes energy losses. 
   It is still a further object of the present invention to provide a vacuum circuit breaker with an integral high speed grounding switch that closes the circuit to ground virtually instantaneously. 
   It is still a further object of the present invention to provide a vacuum circuit breaker with an integral high speed grounding switch that can be operated in the range of 34.5 kilovolts. 
   It is still another object of the present invention to provide a vacuum circuit breaker that is effective for use in association with wind farm energy production. 
   These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention is a circuit breaker apparatus that comprises a housing, a first set of bushings extending outwardly of the housing, a second set of bushings extending outwardly of the housing, a first vacuum bottle positioned in the housing and having pairs of contactors therein, a second set of vacuum bottles positioned in the housing and having pairs of contactors therein, and a mechanical linkage movable between a first position and a second position. One of the pair of the contactors of the first vacuum bottle is electrically interconnected to the second bushing. One of the pair of contactors of the second vacuum bottle is electrically interconnected to ground. The first position serves to electrically connect the first bushing to the second bushing. The second position serves to electrically connect the first bushing to ground. 
   An actuator serves to move the mechanical linkage between the first position and the second position. The first vacuum bottle is in longitudinal alignment with the second vacuum bottle. The mechanical linkage is interposed between the first and second vacuum bottles. 
   The mechanical linkage comprises an actuator arm having the other of the pair of contactors of the first vacuum bottle electrically connected thereto. The actuator arm has the other of the pair of contactors of the second vacuum bottle electrically connected thereto. The pair of contactors of the first vacuum bottle being electrically connected together when in the first position. The pair of contactors of the first vacuum bottle are electrically isolated from each other in the second position. The pair of contactors of second vacuum bottle are electrically isolated from each other in the first position. The pair of contactors of the second vacuum bottle are electrically connected together in the second position. 
   The present invention is also a circuit breaker apparatus that comprises a first vacuum bottle having a first contactor and a second contactor therein, a second vacuum bottle having a first contactor and a second contactor therein, an actuator arm connected at one end to the second contactor of the first vacuum bottle and to the first contactor of the second vacuum bottle, and a means for moving the actuator arm between a first position in which the second contactor contacts the first contactor of the first vacuum bottle and a second position in which the first contactor contacts the second contactor of the second vacuum bottle. The second contactor of the second vacuum bottle is connected to ground. The actuator arm is interconnected to a supply of power. In particular, a power supply is connected by a line to the actuator arm. A substation is connected by a line to the first contactor of the first vacuum bottle. Power is passed from the power supply to the substation when the actuator arm is in the first position. The power supply has a three phase current. As such, the first vacuum bottle includes three vacuum bottles and the second vacuum bottle comprises three vacuum bottles. The first contactor in each of the three vacuum bottles is connected to a separate phase of the power supply. The actuator arm is electrically interconnected to a first bushing. The first contactor of the first vacuum bottle is connected to a second bushing. The first bushing is connected to the power supply while the second bushing is connected to the substation. At least one first current transformer extends around the first bushing. A second current transformer extends around the second bushing. The power supply will have a nominal voltage of 34.5 kilovolts or lower. 
   The present invention is also a system for passing energy from a power supply to substation. This system comprises a bus suitable for passing energy from the power supply, a line connected to ground, a circuit suitable for passing energy from the bus to the substation, and a circuit beaker interconnected between a contactor of the bus and a contactor of the line and a contactor of the circuit. The circuit breaker has means for mechanically and selectively connecting the contactor of the bus to the contactor of the circuit and for connecting the contactor of the bus to the contactor for the line. The first vacuum bottle has the contactor for the bus and the contactor for the circuit therein. The second vacuum bottle has the contactor for the line therein. The mechanical interlock extends between the first and second vacuum bottles and is electrically interconnected to the bus. The plurality of wind energy generators are connected to the bus. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       FIG. 1  is a block diagram showing the operation of a prior art circuit breaker system. 
       FIG. 2  is a block diagram showing the circuit breaker system of the present invention. 
       FIG. 3  is a side interior view of the circuit breaker of the preferred embodiment of the present invention. 
       FIG. 4  is a frontal elevation of the circuit breaker of the preferred embodiment present invention. 
       FIG. 5  is an illustration of the mechanical interlock of the present invention in combination of the first and second vacuum bottles with the mechanical interlock in the first position. 
       FIG. 6  is an illustration of the operation of the mechanical interlock of the present invention with the mechanical interlock in a second position. 
       FIG. 7  is a graph showing the switch operation of the circuit breaker of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIG. 2 , there is shown the system  42  of the present invention. The circuit breaker system  42  of the present invention includes the circuit breaker apparatus  44  as used for transferring energy upon the opening of the circuit to ground  46 . A plurality of wind energy generators  48 ,  50 ,  52  and  54  are connected by respective conductors  56 ,  58 ,  60  and  62  to a bus  64 . The wind energy generators  48 ,  50 ,  52  and  54  can be a portion of a wind farm. As such, various busses  64  can also be connected to a main energy transfer bus  66 . Ultimately, the energy is transmitted along line  68  to the circuit breaker  44 . When the circuit breaker  44  is suitably closed, then the energy will be delivered along line  70  to substation  72 . It can be seen in  FIG. 2  that the bus  64  does not include the grounding transformer  30  of the prior art. As such, it is the goal of the circuit breaker  44  (with grounding switch) to switch the energy to ground  46  as quickly as possible, preferably, within one cycle (i.e., within 16 milliseconds). 
     FIG. 3  shows the circuit breaker  44  of the present invention. Circuit breaker  44  includes a housing  74  having a weather proof roof  76  extending thereover. A first bushing  78  and a second bushing  80  extend outwardly of the housing  74  and through the roof  76 . Bushing  78  will extend to the wind farm side of the circuit. Bushing  80  will extend to the substation side of the circuit. A first current transformer  82  is positioned over the bushing  78 . The current transformer  82  is a doughnut-shaped transformer which serves to detect the amount of current passing through the first bushing  78 . As such, the current transformer  82  serves to monitor the power, and the quality of power passing through bushing  78 . The current transformer  82  can be electrically interconnected to a suitable relay for opening and closing the circuit breaker in the event of the detection of a problem with the power transmission, or other requirements of the opening or closing of the circuit breaker. 
   The bushing  80  has another current transformer  84  extending therearound. Current transformer  84  is a configuration similar to that of current transformer  82 . Current transformer  84  serves to sense the power, and the quality of power passing outwardly of the circuit breaker  44  and to the substation. Once again, the current transformer  84  can be suitably interconnected to proper relays so as to open and close the circuit breaker  44  in the event of a problem condition. 
   A busbar  86  connects the bushing  78  to the mechanical interlock  88 . The mechanical interlock  88  is interposed between a first vacuum bottle  90  and a second vacuum bottle  92 . Another busbar  94  is located at the top of the first vacuum bottle  90  and extends in electrical connection to the second bushing  80 . The second vacuum bottle  92  includes a grounding bar  96  suitably connected to ground. Supports  98 ,  100  and  102  will maintain the vacuum bottles  90  and  92 , along with the mechanical interlock  88 , in a longitudinally aligned orientation extending substantially vertically within the interior of the housing  74 . A suitable operating and communication mechanism  104  is cooperative with the mechanical interlock  88 . Control push buttons and indicating lamps  106  are located on a wall of the enclosure  74  so as to provide a humanly perceivable indication of the operation of the circuit breaker  44  and allowing for manual control of the mechanical interlock  88 . There is an auxiliary terminal block compartment  108  located on an opposite wall of the enclosure  74  from the control push buttons  106 . The housing  74  is supported above the earth by legs  110  (or by other means). 
     FIG. 4  shows a frontal view of the housing  74  of the circuit breaker  44 . Importantly, in  FIG. 4 , it can be seen that the bushing  78  actually includes a first bushing  112 , a second bushing  114  and a third bushing  116  extending outwardly of the roof  76  of housing  74 . The bushings  112 ,  114  and  116  will correspond to the three phases of current passing as energy from the wind farm. Similarly, the second bushing  80  will also have an array of three of such bushings such that the three phases can be passed from the circuit breaker. 
   A door  118  is mounted on the housing  74  so as to allow easy access to the interior of the housing  74 . Legs  110  serve to support the housing  74  above the earth. 
     FIG. 5  illustrates the operation of the mechanical interlock  88  of the present invention. As can be seen, the mechanical interlock  88  includes an actuator arm  120  which extends between the first vacuum bottle  90  and the second vacuum bottle  92 . The busbar  86  is electrically interconnected to the actuator arm  120 . 
   The first vacuum bottle  90  is hermetically sealed in a vacuum condition. The first vacuum bottle  90  includes a first contactor  122  and a second contactor  124  within the interior of the vacuum bottle  90 . The first contactor  122  is connected by conductor  126  in electrical interconnection to the second bushing  80 . The second vacuum bottle  92  includes a first contactor  128  and a second contactor  130 . The second contactor  130  is connected by conductor  132  to ground  46 . 
   In  FIG. 5 , the actuator arm  120  is in its first position. In this position, the contactors  122  and  124  are juxtaposed together so as to be in electrical connection. As such, power passing along busbar  86  will be transmitted through the interior of the first vacuum bottle  90  through conductor  126  to the bushing  80 . The circuit to ground through the second vacuum bottle  92  is open. As such,  FIG. 5  illustrates the normal operating condition of the circuit breaker  44  of the present invention in which the power is passed directly therethrough to the substation  72 . 
   In the event of an interruption, a failure, or a problem, the circuit breaker  44  will open the circuit to the substation so that the electrical energy passing through the busbar  86  is passed to ground  46  instantaneously. As can be seen in  FIG. 6 , the first contactor  122  is electrically isolated from the second contactor  124  within the interior of vacuum bottle  90 . As such, the conductor  126  is electrically isolated from power passing from the busbar  86 . The actuator arm  120  instantaneously separates the contactor  124  from the contactor  122  while, at the same time, establishes an electrical connection between the contactor  128  and the contactor  130  in the second vacuum bottle  92 . As such, the power from the busbar  86  is immediately switched to ground  46 . 
   A variety of techniques can be utilized for moving the actuator arm  120  between the first and second position. For example, latches, springs, magnets, or other devices can be employed so as to instantaneously shift the actuator arm  120  between the first and second positions. Importantly, the vertical alignment of the first vacuum bottle  90  with the second vacuum bottle  92  assures that this mechanical connection instantaneously serves to transfer energy. The present invention avoids the need for electrical interconnections. Experiments with the system of the present invention have indicated that the switching can occur in less than one cycle. 
   In  FIG. 7 , the near instantaneous switching can be easily seen. In  FIG. 7 , channel one is the analogical representation of the main breaker contact traveling. Channel two is the logical representation of the contacts position of both the main breaker and the grounding switch, connected in a parallel circuit. The oscillogram of  FIG. 7  shows that the complete switching sequence (i.e. the time duration for opening the main breaker through closing the grounding switch) is accomplished in 14.76 milliseconds. The main breaker contact traveled more than 75% of its total stroke when the grounding switch is closed. The main breaker (i.e. the upper vacuum interrupts) connects the generator collection circuits to the transformer bus. The high speed, mechanically-interlocked grounding switch (i.e. the lower vacuum interrupters) connects the collection circuits automatically to ground. This occurs with a complete switching sequence of less than one cycle (between 12 to 16 milliseconds). As a result, the transient voltage does not rise enough during the one cycle to be above the limits of the arresters or the allowable rise at the wind turbine controllers. 
   The foregoing disclosure and description of the invention is illustrative and explanatory thereof. Various changes in the details of the illustrated construction can be made within the scope of the appended claims without departing from the true spirit of the invention. The present invention should only be limited by the following claims and their legal equivalents.