Abstract:
An actuation and control device for opening and/or closing high- and medium-voltage circuit breakers having at least one fixed contact and at least one moving contact, comprising actuation means which are operatively connected to the moving contact and supply the energy for performing the opening/closure movement, the particularity of which consists of the fact that the actuation means comprise a servomotor, an electronic control and power supply unit, and elements for transmitting motion, and that the actuation means and/or the coupling between the fixed contact and the moving contact are such as to achieve a desired speed of the moving contact at the instant in which it separates from the fixed contact.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application is a continuation of application number PCT/EP99/05363 filed on Jul. 23, 1999.  
         BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to an actuation and control device for opening/closing switchgear, particularly circuit breakers for high- and medium-voltage transmission and/or distribution networks. The device according to the invention is now described with reference to a high-voltage circuit breaker without intending in any way to limit the scope of its application.  
           [0003]    An example of a single pole of a high-voltage circuit breaker provided with a known type of actuation device is shown schematically in FIG. 1. A first post-shaped supporting insulator  2  is arranged on a supporting frame  1  and a second insulator  3  is arranged on the upper end of said first insulator; an interruption chamber is provided inside said second insulator and has circuit breaking mechanisms which comprise fixed contacts and moving contacts. Opening/closure is performed by engaging/disengaging the fixed contacts with respect to the moving contacts. The moving contacts are operatively connected to an actuation rod which runs, inside the supporting insulator  2 , from the moving contacts to the base of the post. The rod is actuated by means of kinematic systems which are located in a housing  4  at the base of the post and are operatively connected to an actuation device  5 . Actuation devices for high-voltage circuit breakers are currently of the mechanical or hydraulic type.  
           [0004]    The mechanical actuation device generally uses two springs, namely a closure spring and an opening spring, a stroke limit damping system, a reloading motor for the closure spring and a mechanism which allows to convert the motion produced by the springs into a translatory motion of the moving contact, to reload the opening spring and to make the opening movement independent of the closure movement.  
           [0005]    According to a known embodiment, the mechanical actuation is provided by means of the device shown in FIG. 2, in which the following elements can be identified: an opening spring  10 , an opening device  11  actuated by an electromagnet, an eccentric element with a lever  12 , a closure device  13  actuated by an electromagnet, a main shaft  14 , an arm  15  rigidly coupled to the shaft  14 , a closure spring  16 , a damping unit  17 , a drum  18  and a gearmotor  19 .  
           [0006]    Another example of known mechanical actuation device is described in U.S. Pat. No. 5,151,567 and is shown schematically in FIG. 3. In this case, the movement of the main shaft  20  during the opening of the circuit breaker (in the direction of the arrow  28  of FIG. 3) is produced by virtue of the action of a spring  21  which is conveniently positioned and connected to the main shaft  20  by means of the crank  22 . The movement of said rod is allowed by a release mechanism  23 . During closure (direction of the arrow  27  of FIG. 3), the main shaft  20  is moved by means of a motor  24  which is directly coupled to the main shaft  20  and is actuated by an electronic unit  25  supplied by the power supply block  26 . The action of said motor also allows to reload the opening spring  21 . Accordingly, the closure spring is eliminated and the spring  21  is used only during opening, the opening speed being preset by selecting the dimensions of the spring.  
           [0007]    However, in the above solution there is no active control of the position and motion of the actuation shaft  20  during the opening and closure of the circuit breaker.  
           [0008]    Many other configurations are available as an alternative to the illustrated ones, but the mechanical actuation devices of the known art generally have a large number of components which require a long and complicated initial calibration. Despite performing the task to which they are dedicated, these devices have several drawbacks in addition to their already-mentioned mechanical complexity. The movement of the moving contact is in fact determined exclusively by the elastic characteristic of the opening and closure springs: the rule of motion of the moving contact cannot be changed by the user but is set during design. Actuation devices of the hydraulic type, in which the movement of the moving contact is ensured by suitable hydraulic actuators, can partially obviate these drawbacks, but they have disadvantages linked to the presence of fluids, especially owing to their temperature-sensitivity.  
           [0009]    The use of springs and the lack of control over the rule of motion of the actuator furthermore require the presence of damping elements or shock-absorbers in order to dissipate the residual kinetic energy at the end of the movement and to avoid uncontrolled impacts against the pole. Moreover, precision in the positioning of the moving contact is limited by a mechanism which is inherently inaccurate owing to the presence of the springs.  
           [0010]    The energy that must be supplied is furthermore greater than the energy strictly necessary to move the moving contact, since it is also necessary to move the various mechanical elements of the actuation device.  
         SUMMARY OF THE INVENTION  
         [0011]    The aim of the present invention is to provide an actuation and control device for high- and medium-voltage circuit breakers (i.e. for voltages greater than 1000 V) which allows to move the moving contact of said circuit breaker according to a predetermined rule of motion.  
           [0012]    Within the scope of this aim, an object of the present invention is to provide an actuation and control device for high- and medium-voltage circuit breakers whose mechanical complexity is reduced.  
           [0013]    Another object of the present invention is to provide an actuation and control device for high- and medium-voltage circuit breakers which allows to preset the positioning precision of the moving contact both during opening and during closure.  
           [0014]    Another object of the present invention is to provide an actuation and control device for high- and medium-voltage circuit breakers which ensures repeatability of the movement, optionally compensating variations due to aging and wear.  
           [0015]    Another object of the present invention is to provide an actuation and control device for components of high- and medium-voltage circuit breakers which has reduced response times.  
           [0016]    Another object of the present invention is to provide an actuation and control device for components of high- and medium-voltage circuit breakers which is highly reliable, relatively easy to manufacture and at competitive costs.  
           [0017]    Thus, the present invention relates to an actuation and control device for opening and closing high- and medium-voltage circuit breakers having at least one fixed contact and at least one moving contact, said device comprising actuation means which are operatively connected to the moving contact and supply the energy for performing the opening/closure movement. The device according to the present invention is characterised in that said actuation means comprise a servomotor, an electronic control and power supply unit for driving said motor, and elements for transmitting motion between the motor and the moving contact, and it is further characterised in that said actuation means and/or the coupling between the fixed contact and the moving contact are such as to achieve a desired speed of the moving contact at the instant in which it separates from the fixed contact during the opening movement.  
           [0018]    The device according to the invention, in addition to ensuring a desired speed of the moving contact at the instant in which the contacts separate, is furthermore capable of controlling the rule of motion during the entire opening and/or closure movement.  
           [0019]    Control of the speed of the moving contact at the instant in which it separates from the fixed contact allows to optimize the quenching times of the electric arc between the contacts.  
           [0020]    Control of the rule of motion of the moving contact allows to ensure the accuracy and repeatability of the movement. The actuation device is furthermore highly simplified with respect to known types of actuation system, since it allows to eliminate springs of the spiral or other type, the motor for reloading the closure spring, and all the mechanisms that allow to perform the movement cycle; accordingly, the space occupation is also reduced. Furthermore, as a consequence of constructive simplicity, the need for maintenance interventions is reduced.  
           [0021]    The elements for transmitting motion between the motor and the moving contact and the coupling between the moving contact and the fixed contact furthermore ensure the movement of said moving contact at a desired speed without this entailing an oversizing of the servomotor. The term servomotor is generally used to define motors having a feedback control system.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]    Further characteristics and advantages of the invention will become apparent from the description of some preferred but not exclusive embodiments of an actuation and control device for opening and/or closing high- and medium-voltage circuit breakers, illustrated only by way of non-limitative example in the accompanying drawings, wherein:  
         [0023]    [0023]FIG. 1 is a schematic view of a pole of a circuit breaker provided with an actuation device of a known type;  
         [0024]    [0024]FIG. 2 is a schematic view of an example of a mechanical actuation device of a known type;  
         [0025]    [0025]FIG. 3 is a schematic view of another example of a mechanical actuation device of a known type;  
         [0026]    [0026]FIG. 4 is a block diagram of an actuation and control device according to the invention;  
         [0027]    [0027]FIG. 5 is a view of an example of a first embodiment, according to the invention, of elements for transmitting motion between the motor and the moving contact;  
         [0028]    [0028]FIG. 6 is a view of another example of an embodiment, according to the invention, of elements for transmitting motion between the motor and the moving contact;  
         [0029]    [0029]FIG. 7 is a view of another example of an embodiment, according to the invention, of elements for transmitting motion between the motor and the moving contact;  
         [0030]    [0030]FIG. 8 is a view of another example of an embodiment, according to the invention, of elements for transmitting motion between the motor and the moving contact;  
         [0031]    [0031]FIG. 9 is a view of another example of an embodiment, according to the invention, of elements for transmitting motion between the motor and the moving contact;  
         [0032]    [0032]FIG. 10 is a view of the same embodiment of FIG. 9 in another movement position;  
         [0033]    [0033]FIG. 11 is a view of another example of an embodiment, according to the invention, of elements for transmitting motion between the motor and the moving contact;  
         [0034]    [0034]FIG. 12 is a schematic view of an example of embodiment of the coupling between the fixed contact and the moving contact of the circuit breaker according to the invention.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0035]    With reference to FIG. 4, the actuation and control device according to the invention comprises a control and power supply unit  30  which, as a consequence of an intervention command  35  (which originates for example from an operator or from a protection system), actuates a servomotor  31  which is operatively connected to a moving contact  33  of the circuit breaker by virtue of suitable motion transmission elements  32 . The moving contact  33  is coupled to a fixed contact  37  by means of a suitable coupling system  36 . The servomotor  31  is driven by the unit  30  so that the moving contact  33  obeys a preset rule of motion. Furthermore, by virtue of the action of the motor and of the structure of the motion transmission elements  32  and/or of the coupling  36 , it is possible to achieve a chosen speed of the moving contact  33  at the instant in which it separates from the fixed contact  37  during the opening movement.  
         [0036]    The control and power supply unit  30  can generally be supplied directly by the network  34 , but it is preferably powered by an energy accumulation system  38 , for example a bank of capacitors, and acts on the servomotor  31 . The use of a servomotor allows to have considerable power available with short delivery times. It is furthermore possible, power levels being equal, to act with two independent control parameters (torque and/or speed), allowing greater flexibility during design.  
         [0037]    Furthermore, the use of motion transmission elements  32  which have an appropriate structure and/or the adoption of a suitable coupling  36  between the moving contact  33  and the fixed contact  37  allow to optimize the scaling of said servomotor, achieving the chosen speed of the moving contact during the opening movement without thereby requiring an excessive power on the part of the servomotor. This allows a further reduction in the manufacturing costs of the device according to the invention.  
         [0038]    Some nonlimitative examples of possible embodiments of said elements for transmitting motion between the servomotor and the moving contact are shown schematically in FIGS.  5  to  9 .  
         [0039]    In a first embodiment of the device according to the invention, the elements for transmitting motion between the servomotor and the moving contact are provided so that for an initial period after the opening command the movement applied by the servomotor  31  is not transmitted to the moving contact  33 .  
         [0040]    With reference to FIG. 5, the guiding rod of the moving contact  402  is constituted at least partially by a sleeve  400  inside which a rod  41  can move freely; said rod is connected to the main actuation shaft. When the opening command occurs, the main actuation shaft, connected to the servomotor  31 , causes the rod  41  to slide in the direction indicated by the arrow  44 . After traveling the distance  45  indicated in the figure, the rod  41 , by virtue of a raised portion  43  formed thereon, engages the rod  402  at the edge  42  of the sleeve  400 . In this manner, the rod  402  and therefore the moving contact  33  of the circuit breaker are moved monolithically in the direction indicated by the arrow  44 .  
         [0041]    During the closure of the circuit breaker, the main actuation shaft, connected to the servomotor  31 , actuates the rod  41  in the direction of the arrow  46  until the raised portion  43  abuts against the rod  402 .  
         [0042]    Suitable damping means can be introduced in order to make the contact between the rod  41  and the rod  402  more gradual. FIG. 5 shows, for the sake of simplicity, an example of said damping means, constituted by a pad  401  which is interposed between the rod  41  and the rod  402 . Alternative embodiments may also provide for the interposition of said damping pad  401  also between the raised portion  44  of the rod  41  and the edge  42  of the sleeve  400 .  
         [0043]    The embodiment of FIG. 5 is advantage in that during the opening of the circuit breaker the moving contact begins its separation from the fixed contact with a nonzero initial speed. If the geometry of the moving contact and of the fixed contact is known, it is possible to set the dimensions of the gap  45  so that the moving contact has a preset speed at the instant in which it separates from the fixed contact.  
         [0044]    Another example of an embodiment of elements for transmitting motion between the servomotor and the moving contact, using the same principle as in FIG. 5, is presented with reference to FIG. 6. In this case, a slot  47  is formed in the guiding rod  40  of the moving contact and a pivot  48  slides therein; said pivot is connected, by means of the support  49 , to the rod  50  which is connected to the main actuation shaft, which is in turn actuated by the servomotor. The slot  47  can be a through slot, as shown in FIG. 6. As an alternative, the coupling between the rod  40  and the pivot  48  can be provided by means of a suitable slot formed on the outer surface of the rod  40 .  
         [0045]    During the opening movement, the main actuation shaft causes the sliding of said pivot  48  in the direction of the arrow  51  over the entire length of the slot  47 . At the end of the stroke along said slot  47 , the pivot  48  engages the rod  40 , causing the moving contact connected to said rod  40  to move with a nonzero initial speed. As in the embodiment described in the preceding case, if the geometry of the moving contact and of the fixed contact is known, it is possible to set the dimensions of the slot  47  so that the moving contact has a preset speed at the instant in which it separates from the fixed contact.  
         [0046]    During the closure movement, the rod  50  is moved by the main shaft in the direction of the arrow  52 , moving the pivot  48  into abutment at the opposite end of the slot  47 . In this manner, the rod  40  moves rigidly with the rod  50  until the circuit breaker closes completely.  
         [0047]    As in the case of FIG. 5, the use of damping systems can be provided for this embodiment also.  
         [0048]    In another embodiment of the device according to the invention, the elements for transmitting motion between the servomotor and the moving contact are provided so as to form a variable motion transmission ratio.  
         [0049]    According to the embodiment shown in FIG. 7, a crank  62  is connected to the main actuation shaft  61 , which is actuated by the servomotor  60 ; said crank is in turn connected to the linkage  64  by means of the pivot  63 . The linkage  64  is in turn connected to the guiding rod of the moving contact  640  by means of an articulation  641 . The crank  62  and the linkage  64  allow to convert the rotary motion of the main shaft  61  into a translatory motion of the guiding rod of the moving contact  640 . During the opening movement, the main shaft rotates in the direction of the arrow  65  and the crank  62  moves from an inactive position  66  to a subsequent position  67 . Owing to the very dynamics of the rotation of the crank  62 , the movement of the guiding rod of the moving contact  640  in the direction of the arrow  69  occurs initially at a reduced speed. Then the translatory speed of the guiding rod of the moving contact  640  increases considerably, again because of the rotational dynamics of the crank  62 . Accordingly, by scaling the crank  62  and the linkage  64  appropriately it is possible to make the moving contact separate from the fixed contact with the chosen speed.  
         [0050]    During the closure movement, the servomotor  60  turns the main actuation shaft  61  in the direction of the arrow  68 , rotating the crank  62  from the position  67  to the position  66  and therefore moving the guiding rod of the moving contact  640  in the direction of the arrow  70 , which is the opposite of the preceding one.  
         [0051]    According to the embodiment shown in FIG. 8, a cam or eccentric element  71  is connected to the main actuation shaft  61 . The guiding rod of the moving contact  640  is connected to the cam  71  by means of a roller  72  which can slide freely in a slot  73  formed proximate to the edge of the cam  71 . During the opening movement of the circuit breaker, the servomotor  60  causes a rotation of the main shaft  61  in the direction of the arrow  74 . By virtue of the presence of the roller  72  and of the cam  71 , the rotary motion of the shaft  61  is converted into a translatory motion of the guiding rod  640  in the direction of the arrow  76 . This movement, by virtue of the very geometry of said cam  71 , occurs initially at a reduced speed and then at an increasing speed. As in the embodiment of FIG. 7, it is possible to scale the cam  71  so that the moving contact of the circuit breaker has a preset translatory speed in the direction of the arrow  76  at the instant in which it separates from the fixed contact. During the closure movement, the servomotor  60  rotates the main shaft  61  in the direction of the arrow  75 . The rotation of the cam  71  and the consequent motion of the roller  72  along the slot  73  causes a translatory motion of the guiding rod  640  in the direction of the arrow  77 .  
         [0052]    According to the embodiment shown in FIGS. 9 and 10, a gear  78  is arranged on a secondary shaft  79 . The gear  78  is connected to the linkage  64  by means of the pivot  80 . The linkage  64  is in turn connected to the guiding rod  640  of the moving contact by means of the articulation  641 . The gear  78  is furthermore connected to the main shaft  61 , actuated by the servomotor  60 , by means of the pinion  81 .  
         [0053]    During the opening of the circuit breaker, the servomotor  60  turns the main shaft  61  in the direction of the arrow  82  shown in FIG. 10; by virtue of the pinion  81 , the gear  78  is turned in the direction of the arrow  83 ; this fact produces the translatory motion of the guiding rod of the moving contact  640  in the direction of the arrow  84 . The gear therefore assumes the position  1000  of FIG. 10. By appropriately scaling the pinion  81  and the gear  78  and appropriately choosing the position of the pivot  80  on the gear  78  it is possible to make the translatory motion of the guiding rod of the moving contact  640  in the direction of the arrow  84  occur with the chosen speed at the instant in which the moving contact separates from the fixed contact. During the closure movement, the servomotor  60  turns the main shaft  61  in the direction of the arrow  85  of FIG. 9. This produces a rotation of the gear  78  in the direction of the arrow  86 , with a consequent translatory motion of the guiding rod  640  of the moving contact in the direction of the arrow  87 . The gear therefore assumes the position  1001  of FIG. 9.  
         [0054]    This embodiment appears to be particularly advantageous, since it has an additional parameter to work on for the overall scaling of the system, namely the transmission ratio between the pinion and the gear.  
         [0055]    [0055]FIG. 11 schematically illustrates another embodiment of elements for transmitting motion between the servomotor and the moving contact. According to this embodiment, the servomotor  60  is arranged along the same directrix of motion as the moving contact of the circuit breaker (for example vertically).  
         [0056]    The servomotor  60  is connected to the main actuation shaft  61 , which has, along a certain portion of its length, one or more surface grooves  610  which are arranged on a helical path in the direction of the axis of the shaft  61  and have a variable pitch. In particular, the pitch of said slots  610  increases in the direction indicated by the arrow  611 . Inside each groove there is a ball  612  which is connected, by means of a carriage  613 , to the actuation rod of the moving contact  614 , which is machined so as to have a cylindrical seat  615  which is suitable to accommodate the actuation shaft  61  over a certain portion of its length.  
         [0057]    During the closure movement, the servomotor  60  turns the actuation shaft  61  in the direction of the arrow  616 . The ball  612  is forced to move along the grooves  610  and by virtue of the carriage  613  it induces a translatory motion of the rod  614  in the direction of the arrow  617 . During the opening movement, the servomotor  60  turns the shaft in the direction  618  and induces a translatory motion of the rod  614  in the direction indicated by the arrow  619 . By virtue of the variable pitch of the groove  610 , this movement occurs at a variable speed. By appropriately scaling said pitch of the groove  610 , the rod  614 , the shaft  61  and the servomotor  60 , the moving contact can be made to have a preset speed at the instant in which it separates from the fixed contact.  
         [0058]    In addition and/or as an alternative to the choice and optimization of the elements for transmitting motion between the servomotor and the moving contact of the circuit breaker, the speed with which the moving contact separates from the fixed contact can be preset by means of an appropriate selection and scaling of the system for coupling the fixed contact and the moving contact. A nonlimitative schematic example of a possible embodiment of the coupling between the fixed contact and the moving contact is shown in FIG. 12. In particular, a coupling between the fixed contact and the moving contact according to a so-called tulip structure is shown.  
         [0059]    During the closure movement, the fixed contact  91  is inserted in a tubular structure  90  (that is to say, the moving contact moves in the direction of the arrow  96 ) which is connected to a guiding rod  92  by means of a flange  95 . The electrical contact between the two structures occurs by virtue of a mechanical interference between the fixed contact  91  and the internal surface of said tubular structure  90 , which is conveniently shaped with a flared guiding portion at one of its ends  93 .  
         [0060]    During the opening movement, the moving contact slides on the surface of the fixed contact in the direction of the arrow  94 , maintaining the continuity of the electrical contact over the entire length  97 .  
         [0061]    By appropriately scaling said length  97  according to the power delivered by the servomotor and to the type of the elements for transmitting motion between the servomotor and the moving contact, it is possible to accelerate the moving contact  90  so that at the end of said stroke  97 , that is to say, at the instant in which said moving contact separates from the fixed contact  91 , said moving contact has the intended speed.  
         [0062]    The speed at contact separation time is calculated so as to optimize the quenching time of the electric arc that forms between the fixed contact  91  and the moving contact  90  after their separation.  
         [0063]    In practice it has been found that the actuation and control device according to the invention fully achieves the intended aim, since it allows to improve the characteristics of the electrical actuation elements by controlling the rule of motion of the moving contact and ensuring that said moving contact has a preset speed at the instant in which it separates from the fixed contact.  
         [0064]    It has furthermore been observed that the transmission elements as described by way of example in FIGS.  5 - 11  and the coupling between the moving contact and the fixed contact as described by way of example in FIG. 12 allow the separation of the moving contact from the fixed contact to occur with the chosen speed during the opening movement without thereby oversizing the servomotor.  
         [0065]    In addition to the above listed advantages, the actuation and control device allows to reduce costs by reducing the parts, by reducing the calibration operations and by eliminating movements and stresses which can lead to impact damage. Maintenance costs are also reduced accordingly.  
         [0066]    The device thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept; all the details may furthermore be replaced with technically equivalent elements. In practice, the materials used, so long as they are compatible with the specific use, as well as the dimensions, may be any according to the requirements and the state of the art.