Patent Publication Number: US-2009230090-A1

Title: Vacuum switch

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/036,793, filed Mar. 14, 2008, the entire contents of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to a vacuum switch assembly that may be used for initiating or interrupting current flow. More particularly, the present invention is directed to a high voltage vacuum switch comprising two or more vacuum interrupters connected in series and furthermore having a ground position. 
     BACKGROUND OF THE INVENTION 
     Switch assemblies and circuit breakers for initiating or interrupting current flow, such as solid dielectric insulated vacuum loadbreak switches, are known in the art. Such switches are typically designed with an operating handle that is permanently affixed to an actuator, which is then permanently affixed to a movable contact of a vacuum loadbreak bottle. The movable contact engages a fixed contact within the vacuum bottle, thereby creating or breaking an electrical circuit for conducting electricity. This prior art configuration, however, can produce undesirable risk to the lineman working on the switch because it is not possible to determine if the vacuum loadbreak bottle contacts are actually separated when the operating handle indicates that the switch is open. The lineman may mistakenly believe that the switch is open and come into contact with a live circuit. 
     Some prior art switches attempt to resolve this and other issues. For example, many switches use air or SF 6  as the dielectric and switching medium and provide a viewing window, allowing the lineman to see when the switch is in the OPEN or CLOSED positions. These switches have drawbacks, however. The air dielectric switches are substantially large in size and the SF 6  insulated switch can fail if the SF 6  leaks out, which can create environmental problems as well. 
     A vacuum loadbreak switch also carries the risk of leakage, which creates another hazardous condition. If there is a leak in the vacuum loadbreak bottle, the dielectric strength would be lost between the contacts in the loadbreak bottle and a full circuit voltage can develop on the open circuit side of the bottle. Another inherent drawback is that the contacts within the bottle can weld together during a fault-close operation. If the contacts are welded together sufficiently, the contacts may remain in contact with each other even when the switch is moved to the OPEN position, thus maintaining the full circuit voltage. The lineman would be unaware of the circuit voltage and instead would expect the load side to be de-energized when opening the switch. 
     In light of the prior art discussed herein, it is desirable to provide a vacuum switch that provides the lineman with a backup contingency to the single vacuum load break bottle. It is also desirable to provide a vacuum switch that is not substantially large in size and which reduces the risk of voltage appearing on the LOAD side when the switch is in the OPEN position. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a novel vacuum switch assembly. An embodiment of the vacuum switch described herein comprises two vacuum bottles connected in series, constructed and arranged such that if one vacuum bottle fails such as by leaking or if the contacts become permanently welded together, the other vacuum bottle can act as a redundant back-up. Preferably, a visual indicator is provided to alert the user, such as the lineman, of the status of the mechanism operating each vacuum bottle (e.g.; mechanism OPEN or mechanism CLOSED). The visual indicator can take many forms, such as a lever, a button, a sign, etc. The vacuum switch preferably has a first position wherein the two vacuum bottles are closed, and a second position wherein the two vacuum bottles are open. 
     Preferably, the invention further comprises a GROUND position wherein one of the current carrying elements, such as the load-side, is grounded, thereby providing further safety. A third vacuum bottle can be provided, preferably also in series with the load-side vacuum bottle, wherein the third bottle can preferably be for grounding the vacuum switch. Preferably, the vacuum switch includes a GROUND position wherein the line-side vacuum bottle is in the open position. 
     Each vacuum bottle can include, by way of non-limiting example, a fixed contact and a movable contact therein for opening and closing the vacuum bottle. Accordingly, when a vacuum bottle is in the open position, the two contacts are physically separated without a current flow therebetween thus insulating the terminals connected to the switch. A vacuum bottle in a closed position can include two contacts that are electrically connected, more preferably in physical contact with each other, thus electrically connecting the terminals. 
     Thus, it is an object of the present invention to provide a method and apparatus for initiating or interrupting current flow that substantially reduces and/or eliminates the risk of current flowing in the apparatus when current interruption is indicated. 
     Also, it is an object of the present invention to provide a method and apparatus for initiating or interrupting current flow that provides for a terminal to be grounded. 
     Other objects, features, and characteristics of the present invention, as well as the methods of operation and functions of the related elements of the structure, and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following detailed description with reference to the accompanying drawings, all of which form a part of this specification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A further understanding of the present invention can be obtained by reference to a preferred embodiment set forth in the illustrations of the accompanying drawings. Although the illustrated embodiment is merely exemplary of systems for carrying out the present invention, both the organization and method of operation of the invention, in general, together with further objectives and advantages thereof, may be more easily understood by reference to the drawings and the following description. The drawings are not intended to limit the scope of this invention, which is set forth with particularity in the claims as appended or as subsequently amended, but merely to clarify and exemplify the invention. 
       For a more complete understanding of the present invention, reference is now made to the following drawings in which: 
         FIG. 1  is a perspective view of a switch according to an embodiment of the present invention; 
         FIG. 2  is an alternate perspective view of the switch of  FIG. 1 ; 
         FIG. 3  is a schematic view of the switch of  FIG. 1  in the CLOSED position; 
         FIG. 4  is a schematic view of the switch of  FIG. 1  in a first OPEN position; 
         FIG. 5  is a schematic view of the switch of  FIG. 1  in a second OPEN position; 
         FIG. 6  is a schematic view of the switch of  FIG. 1  in the GROUND position; and 
         FIG. 7  is a front view of a switch according to an embodiment of the present invention in the GROUND position. 
     
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
     Referring generally to  FIGS. 1-6 , a switch  1  in accordance with an embodiment of the present invention is shown. In general terms, switch  1  comprises a housing  600  having a line bushing, generally indicated as  10 , and a load bushing, generally indicated as  20 , that are substantially consistent with bushings known in the art. In accordance with an embodiment of the invention, switch  1  includes a first vacuum bottle  100  and a second vacuum bottle  200  electrically connected in series within housing  600 . An embodiment of the switch  1  preferably also includes a ground pad, generally indicated as  30  and a third vacuum bottle referred to herein as ground bottle  300  electrically connected in series with second vacuum bottle  200  but in an OPEN position when switch  1  is in the CLOSED or OPEN positions. 
     In general terms, a lever  501  is connected to an actuating assembly  400  which can be used to electrically connect and disconnect line bushing  10  and load bushing  20 , or to ground switch  1 . Preferably, first vacuum bottle  100 , second vacuum bottle  200 , and ground bottle  300  each include a movable contact ( 122 ,  222 ,  322 , respectively), which is selectively displaceable toward and away from a fixed contact ( 121 ,  221 ,  321 , respectively). Preferably, movable contact  122 ,  222 ,  322  can be displaced away from fixed contact  121 ,  221 ,  321  until movable contact  122 ,  222 ,  322  is electrically disconnected from fixed contact  121 ,  221 ,  321 , wherein the vacuum bottle  100 ,  200 ,  300  is in the OPEN position. Preferably, a gap  123 ,  223 ,  323  exists between movable contact  122 ,  222 ,  322  and fixed contact  121 ,  221 ,  321  when in the OPEN position. In accordance with an embodiment of switch  1 , gap  123 ,  223 ,  323  is between approximately 0.10 and 0.70 in, more preferably between approximately 0.25 and 0.50 in, and most preferably approximately 0.25 in. 
     In the embodiment shown, fixed contacts  121 ,  221 ,  321  are connected to line bushing  10 , load bushing  20 , and ground pad  30 , respectively, and movable contacts  122 ,  222 ,  322  are connected to actuating assembly  400 . Furthermore, movable contact  122 ,  222 ,  322  can be displaced toward fixed contact  121 ,  221 ,  321  until movable contact  122 ,  222 ,  322  is electrically connected to fixed contact  121 ,  221 ,  321 . Preferably, air gap  123 ,  223 ,  323  is reduced until movable contact  122 ,  222 ,  322  is physically in contact with fixed contact  121 ,  221 ,  321 , thus eliminating gap  123 ,  223 ,  323 . 
     In accordance with an embodiment of switch  1 , lever  501  can be placed in a CLOSED position (as seen in  FIG. 3 ) wherein first vacuum bottle  100  and second vacuum bottle  200  are in the CLOSED condition, thus electrically connecting line bushing  10  and load bushing  20  while ground bottle  300  remains in the open condition. As shown, movable contact  122 ,  222  and fixed contact  121 ,  221  are physically in contact with each other within vacuum bottles  100 ,  200 , thus permitting electricity to flow therebetween and thus between line bushing  10  to load bushing  20 . Ground bottle  300  preferably remains in the OPEN condition. 
       FIG. 4  illustrates an embodiment of switch  1  in a first OPEN position. In the embodiment shown, as lever  501  is moved to the first OPEN position, initially, first vacuum bottle  100  moves to an OPEN condition whereas second vacuum bottle  200  remains in a CLOSED condition. Ground bottle  300  preferably remains in an OPEN condition. As shown, a first gap  123  is present between first movable contact  122  and first fixed contact  121 , thus electrically disconnecting first movable contact  122  from first fixed contact  121 . Therefore, line bushing  10  and load bushing  20  are preferably electrically disconnected. 
     As lever  501  continues to a second OPEN position, as shown in  FIG. 5 , wherein the second vacuum bottle  200  is moved to an OPEN condition. Thus when lever  501  is in the second OPEN position, both first vacuum bottle  100  and second vacuum bottle  200  are in the OPEN condition. As shown, a second gap  223  can be present between second movable contact  222  and second fixed contact  221 , thus electrically disconnecting second movable contact  222  from second fixed contact  221 . In the embodiment shown, first vacuum bottle  100  remains in the OPEN position. Therefore, two air gaps  123 ,  223  can be present, thus providing two breaks in the circuit in switch  1 . Accordingly, should there be a leak in first vacuum bottle  100 , wherein first movable contact  122  is electrically connected to first fixed contact  121  notwithstanding the presence of first gap  123 , switch  1  can remain electrically disconnected because second vacuum bottle  200  can remain in an OPEN condition and prevent electric flow. This substantially eliminates the risk of a lineman accidentally coming into contact with a live circuit because of a mistaken belief that the switch is open as indicated, which is a hazard posed by the prior art switches. 
     As shown in  FIG. 6 , an embodiment of switch  1  provides for an additional position, the GROUND position. As lever  501  is moved to the GROUND position, bottle  200  and bottle  300  can each move to a closed condition. Preferably, switch  1  is already in the second OPEN position when entering the GROUND position, and therefore first vacuum bottle  100  is already in an open condition thus preventing the grounding of the cable circuit connected to line bushing  10 . As shown, vacuum bottles  200 ,  300  are in a closed position, thus electrically connecting the electric circuit connected to load bushing  20  and ground pad  30 . Alternatively, second vacuum bottle  200  may remain in the OPEN position, by way of non-limiting example, by internal wiring between second bottle  200  and ground bottle  300  while providing the connection of load bushing  20  to ground pad  30 . 
     In general terms, actuating assembly  400  preferably comprises a first shaft  401  connected to a first cam  410 , which is preferably connected to first movable contact  122  of first vacuum bottle  100 . A second shaft  402  can also be provided in actuating assembly  400 , wherein second shaft  402  is connected to a second cam  420 , which is preferably connected to second movable contact  222  of second vacuum bottle  200 , and a third cam  430  connected to third movable contact  322  of ground bottle  300 . Accordingly, as lever  501  is moved between the different positions, shafts  401 ,  402  can be displaced, thus selectively moving movable contacts  122 ,  222 ,  322  toward or away from fixed contacts  121 ,  221 ,  321 . By way of non-limiting example, actuating assembly  400  can include a third shaft  403  connected to lever  501  and shafts  401 ,  402  such that as lever  501  pivots between the various positions (CLOSED, first OPEN, second OPEN, GROUND), third shaft  403  can rotate to selectively displace first shaft  401  and/or second shaft  402 . First shaft  401  and second shaft  402  can engage third shaft  403  via a cam mechanism or any other suitable mechanism as a matter of application specific design choice. Preferably, actuating assembly  400  includes a plurality of springs  412 ,  422 ,  432  connected to movable contacts  122 ,  222 ,  322  to urge movable contacts  122 ,  222 ,  322  toward fixed contacts  121 ,  221 ,  321 , respectively. Springs  412 ,  422 ,  432  can be extended and contracted by controlling the pressure applied thereon, such pressure being controlled by the respective shaft  410 ,  420 . 
     In accordance with an embodiment of switch  1  illustrated in  FIG. 7 , housing  600  can include a plurality of indicators, such as signs indicating the status of switch  1 . For example, when lever  501  is positioned such that switch  1  is in the CLOSED position, represented by the dashed lines indicated generally as  501   a , a sign indicating the same can be provided on housing proximate lever  501 , as shown. A second sign indicating that switch  1  is in the first OPEN position can also be provided proximate the corresponding position of lever  501 , represented by the dashed lines indicated generally as  501   b . A third sign indicating that switch  1  is in the second OPEN position can also be provided proximate the corresponding position of lever  501  indicated generally as  501   c . Therefore the lineman has an effective visible confirmation that switch  1  is indeed open, and that no electric current is flowing therewithin. A sign indicating ground, preferably a fourth sign, can also be provided on housing  600  proximate the corresponding position of lever  501 , indicated in dashed lines at  501   d , when switch  1  is in the GROUND position. 
     In accordance with an embodiment of switch  1 , lever  501  can pivot between the various positions to open, close or ground switch  1 . By way of non-limiting example, lever  501  can be horizontal when switch  1  is CLOSED, at an angle of about 120° when switch  1  is in the second OPEN position, and at an angle of about 140° when switch  1  is in the GROUND position. The signs can be provided on housing  600  accordingly. 
     Preferably, an additional indicator of GROUND position is provided. For example, lever  501  can be obstructed by a mechanical button  620  or other obstruction, which must be cleared before switch  1  can be grounded. In the embodiment shown, mechanical button  620  extends outward from housing  600  such that lever  501  cannot be moved past mechanical  620  unless mechanical button  620  is depressed. Therefore, the embodiment of switch  1  can ensure that the lineman is aware and intends to ground switch  1  and substantially prevents inadvertent grounding of switch  1 . 
     Whereas the embodiments illustrated in  FIGS. 1-7  comprises a manual lever  501  that actuates actuating assembly  400 , for example, by causing shaft  440  to rotate, it is to be understood that alternate embodiments of the actuating assembly  400  can be used, as a matter of application specific design choice. For example, an automated system such as a computer-controlled motor may be used to change the status of the switch instead of a manual handle without departing from the spirit and the principles of the invention. Alternatively, a motorized bolt can be used, which is preferably controlled remotely, thus providing additional safety for the lineman. Multiple levers  501  can be used, for example, a lever for each vacuum bottle  100 ,  200 ,  300 , or a first lever for first vacuum bottle  100  and a second lever for second vacuum bottle  200  and ground bottle  300 , or any combination thereof, without deviating from the scope of the invention. 
     Switch  1  is preferably capable of operating to 15 kV of electricity, more preferably between 4 kV to 15 kV, most preferably either 4 kV or 15 kV. 
     While the present invention has been described with reference to one or more embodiments set forth in considerable detail for the purposes of making a complete disclosure of the invention, such embodiments are merely exemplary, and are not intended to limit or represent an exhaustive enumeration of all aspects of the invention. Further, it will be apparent to those of skill in the art that numerous changes, for example, the layout or positioning of the vacuum bottles, line, load, ground, shaft, cams, movable contacts, fixed contacts, the type of actuating assembly used, angles of operation between each of the positions, etc. may be made without departing from the spirit and the principles of the invention. The scope of the invention, therefore, shall be defined solely by the following claims.