Patent Publication Number: US-8541702-B2

Title: Folding high voltage electric power switch

Description:
TECHNICAL FIELD 
     The present invention relates to electric switchgear and, more particularly, relates to folding high voltage electric power switch that allows assembly, testing and adjustment of all major components at the factory, folding of the switch for transportation, and minimal assembly in the field largely limited to folding out and securing supports beams and struts with a small number of bolts. 
     BACKGROUND OF THE INVENTION 
     High voltage electric power line switches are used for a variety of purposes, such as interrupting current to loads and other circuit devices. Higher voltage switches are physically larger than lower voltage switches due to the required insulating distances. While switches generally rated for sub-transmission voltages (e.g., approximately 25 kV and below) are physically small enough to be assembled at a factory and transported on a road truck fully assembled, higher voltage transmission switches (e.g., above 25 kV) are generally too large to be transported on a road truck when fully assembled. As a result, higher voltage transmission switches are conventionally shipped as disassembled components, which have to be assembled, adjusted and tested in the field at the line installation site. Of course, field locations are generally outdoors while the factory provides a convenient indoor assembly and testing location. As electric power lines run in all types of terrain, assembly, adjustment and testing of the switch in the field can be difficult. Although assembly, adjustment and testing in the factory would be preferable, this approach has not been available for higher voltage transmission switches. 
     There is, therefore, a continuing need for improved assembly, adjustment and testing techniques for high voltage transmission switches that minimize field assembly while still allowing the switches to be transported by road truck. 
     SUMMARY OF THE INVENTION 
     The present invention meets the needs described above in a folding high voltage electric power switch that can be fully assembled, adjusted and tested at the factory and then folded for shipping on a road truck with minimal disassembly. The platform includes structural beams and struts that easily fold for transportation and unfold for installation in the field while the beams, struts, insulators and blade arms remain attached together. This allows for complete assembly, testing and adjustment of the switch at the factory while limiting the field assembly to simple unfolding and securing together the structural components of the switch platform. 
     The folding electric power switch includes a number of phase insulators (typically two for a two-way switch and three for a three-way switch), a central switch insulator, and a number of blade arms, each selectively connecting an electric power tap at the central insulator to an electric power tap at a respective phase insulator. The insulators are supported by a platform that includes one or more structural beams and one or more struts. The platform folds for transportation with the insulators, power taps, blade arms, structural beams and struts remaining attached to each other. The platform then easily unfolds for installation in the field having been previously assembled, adjusted and tested back at the factory. 
     More specifically, the platform may fold and unfold through pivotal articulation of the structural beams and struts. A two-way switch includes two phase insulators and a three-way switch includes three phase insulators. For the three-way switch, the platform includes a central structural beam and two lateral structural beams pivotally connected to the central beam. The central beam supports the central switch insulator and one of the phase insulators while each lateral beam supports a respective phase insulator. A first strut pivotally is connected to the central beam and removably connected to one lateral beam. Similarly, a second strut is pivotally connected to the central beam and removably connected to the second lateral beam. Each strut typically includes an upper rail and a lower rail allowing the strut to straddle its associated lateral beam when folded. 
     A method for reading the switch for installation includes assembling, adjusting and testing the switch at the factory. A few bolts are then removed and the switch is folded, loaded on a road truck, and transported to the installation site. The switch is unloaded in the field, unfolded and secured in the unfolded configuration through installation of the bolts. This readies the switch for installation in the with minimal field assembly, having been fully assembled, adjusted and tested back at the factory. 
     In view of the foregoing, it will be appreciated that the present invention provides an improved high voltage line switch and method for readying the switch for installation that minimizes field assembly while still allowing the switch to be transported by road truck. The specific structures and techniques for accomplishing the advantages described above will become apparent from the following detailed description of the embodiments and the appended drawings and claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of the folding high voltage line switch. 
         FIG. 2  is a perspective view of the folding high voltage line switch with two of the blade arms placed in position for folding the switch. 
         FIG. 3  is a perspective view of the folding high voltage line switch folded for transportation by road truck. 
         FIG. 4  is a top view of the folding high voltage line switch folded for transportation by road truck. 
         FIG. 5  is a top view of the folding high voltage line switch with the blade arm for a first phase shown in the open position. 
         FIG. 6  is a top view of the folding high voltage line switch with the blade arm for a second phase shown in the open position. 
         FIG. 7  is a top view of the folding high voltage line switch with the blade arm for a third phase shown in the open position. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The present invention may be embodied in a folding high voltage electric power switch that can be fully assembled, tested and adjusted in the factory and then folded for shipping on a road truck with minimal disassembly. The platform includes structural beams and struts that easily fold for transportation and unfold for installation in the field with minimal field assembly largely limited to folding out and securing of support beams and struts. 
     More specifically, the foldable switch includes a number of phase insulators (e.g., two phase insulators for a 2-way switch and three phase insulators for a three-way switch), a central switch insulator and a number of blade arms, each selectively connecting an electric power tap at the central insulator to an electric power tap at a respective phase insulator. The platform that supports the insulators folds with the insulators, power taps, blade arms, structural beams and struts of the platform remaining attached to each other for transportation. This allows the platform to be unfolded and readied for installation through pivotal articulation and securing together the attached structural beams and struts. 
     The switch is typically configured as a two-way switch or a three-way switch. The two-way switch includes two phase insulators and a central switch insulator, while a three-way switch includes three phase insulators and the central switch insulator. Each insulator has an associated power tap for forming switched connections through the blade arms of the switch. The three-way switch therefore includes the central insulator, three phase insulators and three blade arms. The platform for the three-way switch includes a central structural beam and two lateral structural beams pivotally connected to the central beam. The central beam supports the central switch insulator and one of the phase insulators while each lateral beam supports a respective phase insulator. A first strut is pivotally connected to the central beam and removably connected to the first lateral beam. Similarly, a second strut is pivotally connected to the central beam and removably connected to the second lateral beam. Each strut typically includes an upper rail and a lower rail allowing the strut to straddle the lateral beam when folded. 
     The switch can be easily folded by removing the bolts connecting the struts to the lateral beams, articulating the blade arms to be substantially in line with the central beam, articulating the struts to be substantially in line with the central beam, and articulating the lateral beams to be substantially in line with the central beam. This folds the switch into a linear configuration that can be carried on a road truck. Once the switch has been delivered to this installation site, it is easily unfolded by articulating the blade arms, lateral beams and struts into place, bolting the lateral beams to a fulcrum at the central beam, and bolting the struts to the central beam. This readies the switch for installation without the need for additional assembly, adjustment or testing in the field prior to connecting the switch to the grid. 
     Turning now to the figures,  FIG. 1  is a perspective view of the folding electric power switch  10 , which is shown in the unfolded position ready for installation.  FIG. 2  shows the switch partially folded and  FIGS. 3 and 4  show the switch fully folded for transportation. The switch is fully assembled in the factory, where all of the mechanism are fully tested and adjusted. Once the switch has been fully tested and adjusted, it is folded, loaded on a road truck, and delivered to the installation location. There the switch is unloaded and unfolded to ready the switch for installation without having to adjust the switch mechanism or test the switch in the field. This is a significant advantage over conventional high voltage switch installation because it is much easier to assemble, test and adjust the switch at the factory as opposed to in the field. 
     In this particular example, the switch  10  includes electric switchgear forming a three-way switch supported by a folding platform  20 . The electric switchgear includes three phase insulators  12   a - c , each having an associated power tap  14   a - c  and blade arm  16   a - c . Each blade arms selectively connects a power line connected to its associate power tap to a corresponding central power tap  17   a - c  at a central insulator  18  to selectively form switched electrical connections between the insulator power taps and central power taps. The invention may be practiced with any type of suitable switch action. For example, a manual, motor or spring driven actuator can be used to drive each blade arm from the closed position in electrical connection with its associated central power tap (to close the switch leg) to an open position in which the blade arm is not in electrical connection with the associated central power tap (to open the switch leg). In the example switch shown in the figures, the blade arms are rotated approximately 90 degrees clockwise in the horizontal plane to open the switch (i.e., side swing switch operation), although vertical switch action and different amounts of blade arm swing can be implemented if desired. 
     The folding platform  20  includes structural beams and struts. A central structural beam  22  supports the central insulator  18  and one of the phase insulators (phase insulator  12   c  in this example). A first lateral beam  24  supports another phase insulator (phase insulator  12   a  in this example) and a second lateral beam  26  supports the third phase insulator (phase insulator  12   b  in this example). A fulcrum  28  pivotally attaches the lateral beams to the central beam. The fulcrum allows each lateral beam to articulate between an unfolded position transverse to the central beam and a folded position in line with the central beam. 
     A first strut  30  is pivotally attached to the central beam  22  and removably attached to first lateral beam  24 , while a second strut  34  is pivotally attached to the central beam  22  and removably attached to second lateral beam  26 . This allows each strut to articulate between a diagonal unfolded position supporting an associated lateral beam in the transverse position and a folded position in line with the central beam. In addition, the first strut  30  has a split configuration including an upper rail  31  and a lower rail  32  allowing the strut to straddle the first lateral beam  24  when the strut is articulated from the unfolded position (shown in  FIG. 1 ) to the folded position (shown in  FIG. 2 ). Similarly, the second strut  34  includes an upper rail  35  and a lower rail  36  allowing the strut to straddle the second lateral beam  26  when the strut is articulated from the unfolded position (shown in  FIG. 1 ) to the folded position (shown in  FIG. 2 ). 
     The folding operation of the switch  10  is illustrated in the transitions from  FIG. 1  to  FIG. 2  and  FIG. 3 .  FIG. 1  shows the switch in the unfolded position, in which the lateral beams  24  and  26  are transverse to the central beam  22  and held in place by the struts  30  and  34 . That is, the first lateral beam  24  is held in the transverse position by the first strut  30 , which extends diagonally from the distal end of the central beam to the distal end of the first lateral beam. Similarly the second lateral beam  26  is held in the transverse position by the second strut  34 , which extends diagonally from the distal end of the central beam to the distal end of the second lateral beam. In this particular switch, only a few bolts are removed to allow the platform to be folded. There are two bolds fastening the fulcrum  28  to the first lateral beam  24 , one bolt fastening the first strut  30  to the central beam  22  and one bolt fastening the first strut  30  to the first lateral beam  24 . Similarly, there are two bolds fastening the fulcrum  28  to the second lateral beam  26 , one bolt fastening the second strut  34  to the central beam  22  and one bolt fastening the second strut  34  to the second lateral beam  26 . 
     The transition from  FIG. 1  to  FIG. 2  illustrates the first steps in folding the platform. The blade arms  16   a  and  16   b  are articulated from their closed positions (shown in  FIG. 1 ) to open positions (shown in  FIG. 2 ), in which the blade arms  16   a  and  16   b  are substantially in line with the central beam  22 . The bolt securing the first strut  30  to the first lateral beam  24  is removed allowing the first strut  30  to be articulated from its unfolded position (shown in  FIG. 1 ) to its folded position (shown in  FIG. 2 ), in which the first strut  30  is substantially in line with the central beam  22 . The split configuration of the first strut  30  into an upper rail  31  and a lower rail  32  allows the first strut to straddle the first lateral beam as it is articulated from the unfolded position to the folded position. Similarly, The bolt securing the second strut  34  to the second lateral beam  26  is removed allowing the second strut  34  to be articulated from its unfolded position (shown in  FIG. 1 ) to its folded position (shown in  FIG. 2 ), in which the second strut  34  is substantially in line with the central beam  22 . Again, the split configuration of the second strut  34  into an upper rail  35  and a lower rail  36  allows the second strut to straddle the second lateral beam as it is articulated from the unfolded position to the folded position. This places the switch in the partially folded configuration shown in  FIG. 2 . It should be noted that the blade arms are not connected to their actuators at this point, which allows the blade arms to be freely rotated to the desired positions shown in  FIGS. 2 and 3 . 
     To complete the folding operation, one of the bolts fastening the first lateral beam  24  to the fulcrum  28  is removed and the first lateral beam  24  is articulated from its unfolded position (shown in  FIG. 2 ) to its folded position (shown in  FIG. 3 ), in which the first lateral beam  24  is substantially in line with the central beam  22 . The first blade arm  16   a  may be articulated further, as necessary, until the first blade arm  16   a  is substantially in line with the central beam  22  when the first lateral beam  24  is substantially in line with the central beam  22 . Similarly, one of the bolts fastening the second lateral beam  26  to the fulcrum  28  is removed and the second lateral beam  26  is articulated from its unfolded position (shown in  FIG. 2 ) to its folded position (shown in  FIG. 3 ), in which the second lateral beam  26  is substantially in line with the central beam  22 . Again, the second blade arm  16   b  may be articulated further, as necessary, until the second blade arm  16   b  is substantially in line with the central beam  22  when the second lateral beam  26  is substantially in line with the central beam  22 . This places the switch in the fully folded configuration shown in  FIG. 3  allowing the switch to be loaded onto a road truck for transportation. A strap tightened around the folded platform between the phase insulators  12   a - b  and the fulcrum  28  will hold the switch firmly in the folded position.  FIG. 4  shows the folded switch from above. 
     After the switch has been delivered to the installation destination, it is unloaded from the truck and unfolded through a reverse procedure, which involves minimal assembly in the field. Importantly, the switch is readied for installation with very minimal assembly largely limited to swinging the beams and struts into place and installing a few bolts without having to test to adjust the switch mechanisms in the field. 
     The unfolding procedure includes articulation of the first lateral beam  24  from the folded position shown in  FIG. 3  to the unfolded position shown in  FIG. 2 . A bolt is then installed through the fulcrum  28  and the first lateral beam  24  to secure the first lateral beam  24  transverse to the central beam  22  as shown in  FIG. 2 . Similarly, the second lateral beam  26  is articulated from the folded position shown in  FIG. 3  to the unfolded position shown in  FIG. 2 . A bolt is then installed through the fulcrum  28  and the second lateral beam  26  to secure the second lateral beam  26  transverse to the central beam  22  as shown in  FIG. 2 . The first strut  30  is articulated from the folded position shown in  FIG. 2  to the unfolded position shown in  FIG. 1 . A bolt is then installed through the first strut  30  and the first lateral beam  24  to secure the first lateral beam in the transverse position shown in  FIG. 1 . Similarly, the second strut  34  is articulated from the folded position shown in  FIG. 2  to the unfolded position shown in  FIG. 1 . A bolt is then installed through the second strut  34  and the second lateral beam  26  to secure the second lateral beam in the transverse position shown in  FIG. 1 . The blade arms  16   a  and  16   b  are then articulated from their folded positions shown in  FIG. 3  to their unfolded positions shown in  FIG. 1  to ready the switch for installation. 
       FIGS. 5-7  illustrate operation of the switch  10 . For this illustration, the power “line in” is shown attached to the first power tap  14   a , the load is shown attached to the second power tap  14   b , and the “line out” is shown attached to the third power tap  14   c .  FIG. 5  shows the switch  10  with the first blade arm  16   a  open, which disconnects the line in from the load and the line out. This switch operation is useful for isolating the load and the line out from the line in, for example when the line in experiences a short or maintenance outage.  FIG. 6  shows the switch  10  with the second blade arm  16   b  open, which disconnects the load from the line in and the line out. This switch operation is useful for disconnecting the load while keeping the line in connected to the line out to bypass the load. This switch operation is useful for isolating the load from the line, for example when the load experiences a short or maintenance outage.  FIG. 7  shows the switch  10  with the third blade arm  16   c  open, which disconnects the line out from the load and the line in. This switch operation is useful for isolating the load from the line out, for example when the line out experiences a short or maintenance outage. 
     Those skilled in the art will appreciate that additional bolts or different types of fasteners may be used in the switch. It will also be apparent how to configure a two-way switch using the similar techniques. It will be further understood that the foregoing describes a preferred embodiment of the invention and that many adjustments and alterations will be apparent to those skilled in the art within the spirit and scope of the invention as defined by the appended claims.