Abstract:
A three-phase vacuum interrupter switch assembly for power distribution systems comprises an outer case having at least one window and containing a plurality of component assemblies. The case interior is preferably free of oil and/or SF 6  gas. Each component assembly comprises three internal disconnect switch assemblies, three vacuum interrupter bottle switch assemblies and three ground switch assemblies. Each vacuum interrupter bottle switch is coupled in electrical series with a corresponding internal disconnect switch assembly. Because the open/closed state of a bottle switch is not directly observable owing to its sealed interior, a direct visible indication of the state of the three-phase vacuum interrupter switch assembly is provided by a visually detectable contact rod of the corresponding internal disconnect switch that is visible through the case window. To prevent potentially serious damage caused by arcing between the contacts of the internal disconnect switch, the internal disconnect switch is prevented from opening or closing when the bottle switches are closed. 
     When the component assembly is deactivated, some residual current may still remain. The ground switch assembly associated with the component assembly grounds such residual current as part of the deactivation process so that it is safe to have maintenance work performed. An interlocking mechanism ensures that the disconnect switch assembly, vacuum interrupter bottle switch assembly and ground switch assembly of each component assembly are opened and closed in a sequence that ensures proper and safe operation.

Description:
FIELD OF THE INVENTION 
     The present invention pertains to current interrupting switchgear for power distribution systems. More particularly, the present invention relates to a three-phase, four-way, submersible loadbreak vacuum interrupter switchgear with internal ground switches for power distribution systems. More particularly, the present invention relates to a design that can be utilized to make three-phase, multi-way vacuum interrupter switchgear with internal ground switches for power distribution systems. 
     BACKGROUND 
     Electric utility power distribution systems are frequently constructed underground for a variety of reasons ranging from objections to the above-ground aesthetics, the premium of above-ground space in dense urban locations, and safety concerns. Accordingly, power distribution systems heretofore constructed of poles, wires, and pole-mounted switches and transformers are being superseded and even replaced by underground systems in underground “vaults”. 
     In an electric utility power distribution system, switchgear is the combination of electrical disconnect switches, fuses or circuit breakers used to control, protect and isolate electrical equipment. Switchgear is used both to de-energize equipment to allow work to be done and to clear faults down the line. Switchgear is also used to distribute power to different areas within the system. Thus, this type of equipment is important to the distribution of reliable electricity within a power system. 
     The size and weight of three-phase switchgear govern their installation to on-surface or underground locations. While overhead space is relatively open and unrestricted, surface space is somewhat restricted and space in underground installations is more so and at a higher premium. Thus, switchgear have dimensional restrictions imposed on them, especially for underground installations. The size of a regular switchgear using only air as an insulating medium is quite large. In order to reduce size, oil or SF 6  gas was, and is, currently used in many switchgear. However, current environmental concerns discourage the use of these insulating medium. Oil and SF 6  gas can be flammable and/or explosive, and present environmental problems when leakage occurs and when emissions are created. 
     Three-phase, two-way, vacuum interrupter switchgear have been manufactured for use in power distribution systems. The common design of these switchgear is to entirely encapsulate the vacuum bottles in a polymeric material. This design does not allow an operator to visually confirm that the switchgear is in an “open” state and may not safely contain an explosion if the switchgear closes into a fault. These safety hazards were addressed in published U.S. Patent Application No. US-2011-0253675-A1 (the content of which is hereby incorporated by reference) by adding a disconnect switch with viewing window and by encasing the vacuum bottle assemblies within a sturdy stainless steel case. The addition of a viewing window and disconnect switch to the encapsulated design does not, however, address the potential explosion hazard if the switchgear were to close into a fault. 
     SUMMARY OF THE INVENTION 
     The present invention pertains to three-phase, multi-way submersible loadbreak vacuum interrupter switchgear designed to replace oil-insulated and SF 6  gas-insulated switchgear used in three-phase power distribution systems. Aside from the environmental safety aspects addressed by the elimination of oil and SF 6  gas, switchgear constructed in accordance with the present invention also address operational safety aspects by integrating ground switches and using interlocking operating mechanisms to ensure proper operating procedures. Moreover, the preferred component arrangement within switchgear thus constructed embodies a design that can be utilized to easily provide three-phase, multi-way (i.e., 2-way, 3-way, 4-way, 5-way, etc.) vacuum interrupter switchgear with internal ground switches. 
     Accordingly, a three-phase, multi-way submersible loadbreak vacuum interrupter switchgear is described which provides an internal ground switch and meets the dimensional constraints imposed by utility demands while providing the safety and ecological benefits of a vacuum interrupting switch. 
     When switchgear is “turned off”, some residual current may still remain. Vacuum interrupter switch gear herein employs ground switch assemblies associated with the disconnect switch assembly and the vacuum bottle assembly to ground such residual current as part of the deactivation process so that it is safe to have maintenance work performed. 
     A ground can be external or made internal to the switchgear. When a ground switch assembly is built into the switchgear, an interlocking mechanism ensures that the deactivated disconnect switch assembly, deactivated vacuum interrupter bottle switch assembly and the corresponding ground switch assembly are switched in a sequence that ensures proper and safe operation. Conversely, the interlocking mechanism ensures that an activated disconnect switch assembly, activated vacuum interrupter bottle switch assembly and the corresponding ground switch assembly are switched in a sequence that ensures proper and safe operation. an interlocking mechanism can be used to force proper and safe operation. 
     By way of example, a 4-way submersible loadbreak vacuum interrupter switchgear is described and illustrated, but those of ordinary skill in the art will recognize that the number of “ways” may be more or less than 4 without departing from the scope of the invention; the preferred component configuration can in fact simply be repeated sufficiently to make three-phase multi-way switchgear with internal ground switches serving the desired number of branches. Switchgear constructed in accordance with the invention minimizes potential hazards such as oil and gas leakage and explosion in a populated surface location and/or within the confined space of an underground power distribution vault. 
     Other objects, advantages and significant features of the invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the invention. 
     It will be understood that orientations described in this specification, such as “up”, “down”, “top”, “side” and the like, are relative and are used for the purpose of describing the invention with respect to the drawings. Those of ordinary skill in the art will recognize that the orientation of the disclosed device can be varied in practice, and that the orientation used herein has been chosen for explanatory purposes only. Similarly, it will be recognized by those skilled in the art that the materials referred to herein, and particularly those identified by trademark, are examples of materials that meet the requirements and specifications mandated by safety concerns and by the use of the invention with electric power lines. Accordingly, other acceptable materials are within the scope of the invention whether known by generic names and/or other trademarks, or comprising other functionally equivalent material. 
    
    
     
       DESCRIPTION OF THE DRAWING 
       In the drawing, 
         FIG. 1  is a right front perspective view of a preferred three-phase, four-way submersible loadbreak vacuum interrupter switchgear with internal ground switch constructed in accordance with the invention; 
         FIG. 2  is a right front perspective view of the three-phase, four-way submersible loadbreak vacuum interrupter switchgear with internal ground switch of  FIG. 1 , partially broken away to illustrate some internal components; 
         FIG. 3  is a cut-away front elevation view, in schematic, illustrating the internal layout of the ground switch, disconnect switch, and vacuum interrupter bottle switch assemblies in the preferred building block design of the invention; 
         FIG. 4  is a top view, in schematic, of a single-phase building block of  FIG. 3 ; 
         FIG. 5  is a top view, in schematic, of the three-phase building block design of  FIG. 3 ; 
         FIG. 6  is a cut-away right side elevation view, in schematic, of the building block design of  FIG. 3 , illustrating the internal layout of the ground switch assembly components; 
         FIG. 7  is a cut-away right side elevation view, in schematic, of the building block design of  FIG. 3 , illustrating the internal layout of the disconnect switch assembly components; 
         FIG. 8  is a cut-away right side elevation view, in schematic, of the building block design of  FIG. 3 , illustrating the internal layout of the vacuum interrupter bottle assembly components; 
         FIG. 9  is a front elevation view, in schematic, illustrating a preferred design of a three-phase, two-way submersible loadbreak vacuum interrupter switchgear with internal ground switch; 
         FIG. 10  is a cut-away front elevation view, in schematic, of a three-phase, three-way submersible loadbreak vacuum interrupter switchgear with internal ground switch based on  FIGS. 3 and 8 , illustrating the internal layout of components for the ground switch, disconnect switch and vacuum interrupter bottle switch assemblies; 
         FIG. 11  is a cut-away top plan view, in schematic, of a three-phase, three-way submersible loadbreak vacuum interrupter switchgear with internal ground switch of  FIG. 10 , illustrating the internal layout of components for the ground switch, disconnect switch and vacuum interrupter bottle switch assemblies; 
         FIG. 12  is a cut-away front elevation view, in schematic, of the three-phase, four-way submersible loadbreak vacuum interrupter switchgear with internal ground switch of  FIG. 1 , illustrating the internal layout of components for the ground switch, disconnect switch and vacuum interrupter bottle switch assemblies; 
         FIG. 13  is a cut-away top view, in schematic, of the three-phase, four-way submersible loadbreak vacuum interrupter switchgear with internal ground switch of  FIG. 12 , illustrating the internal layout of connection buses to the ground switch, disconnect switch and vacuum interrupter bottle switch assemblies; 
         FIG. 14  is a front elevation view, in schematic, of the three-phase, four-way submersible loadbreak vacuum interrupter switchgear with internal ground switch of  FIG. 12 , illustrating the viewing windows and positions of the handles and rods for the ground and disconnect switches; 
         FIG. 15  is a top elevation view, in schematic, of the three-phase, four-way submersible loadbreak vacuum interrupter switchgear with internal ground switch of  FIG. 14 , illustrating the switch status indicators; 
         FIG. 16  is a front elevation view, in schematic, of the three-phase, four-way submersible loadbreak vacuum interrupter switchgear with internal ground switch of  FIG. 14 , illustrating the attachment of power cables; 
         FIG. 17  is a top elevation view, in schematic, of the three-phase, four-way submersible loadbreak vacuum interrupter switchgear with internal ground switch of  FIG. 15 , illustrating the attachment of power cables; 
         FIGS. 18A-H  are schematic illustrations of the operating handles&#39; preferred interlocking mechanism for ensuring proper opening and closing of the switch assemblies within the switchgear. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     For the sake of brevity, it will be understood that a description of a component having an “a” suffix following its reference numeral will also serve as a description of a corresponding component having a “b”, “c”, “d”, etc. suffix service unless otherwise stated in the specification or as evident from the Figures. Likewise, a set of three corresponding components may be referred to with the suffix “a-c”, “d-f”, “g-i”, and “j-l” following the reference numeral. All corresponding components may be referred to, when appropriate, with the suffix denoting all the corresponding components following the reference numeral: e.g., “a-l”. 
     The currently preferred vacuum interrupter bottle switch assemblies used in the preferred switchgear described herein are the same as the ones in published International Patent Application PCT WO 2009-108729 and the disconnect switch assemblies used are the same as the ones in published U.S. Patent Application No. US-2011-0253675-A1. The content of the foregoing two patent applications are hereby incorporated by reference and, thus, these assemblies will not be discussed in detail here for the sake of brevity. 
     Referring to  FIGS. 1 and 2 , a currently preferred three-phase, four-way, submersible loadbreak vacuum interrupter switchgear with internal ground switch  5  constructed in accordance with the invention is illustrated. The switchgear comprises an outer case  10  formed from a sturdy, corrosive-resistant material. The preferred material is stainless steel. Switchgear case  10  is filled with dry air or nitrogen. Neither oil nor SF 6  gas is used. Case  10  preferably has left side  11   a  (not illustrated), front side  11   b , right side  11   c , and back side  11   d  (not illustrated), bottom  13 , and cover  12  welded together along the abutting edges. Front side  11   b  has operating handles  521   a - d ,  522   a - d , and  523   a - d . Front side  11   b  also has viewing windows  55   a ,  55   b ,  55   c , and  55   d . As will become clear later, the viewing window permits personnel to view power interruption switches inside the sealed case in order to determine if the switches are open or closed. Four sets of three power bushings ( 302   a - c ,  302   d - f ,  302   g - i  and  302   j - l ) extend out from cover  12 . Power bushings  302   a - c  extend up from the far left region of the cover, power bushings  302   d - f  extend from the near left region of the cover, power bushings  302   g - i  extend from the near right region of the cover, and power bushings  302   j - l  extend from the far right region of the cover. Bushing wells can be used in place of power bushings; however, power bushings are the preferred component for this invention. For ease of discussion, this description will refer to each of the foregoing “regions” as a “set”. For example, one can see that there are four sets of power bushings: a first set of bushings  302   a - c , a second set of bushings  302   d - f , a third set of bushings  302   g - i  and a fourth set of bushings  302   j - l . It will be understood that the sets could be defined by other combinations of bushings without departing from the scope of the invention. It will also be understood that outer case  10  is illustrated in  FIGS. 1 and 2  with lines of demarcation visually separating adjacent “sets” of components, that each set is preferably identical in content and layout, and that the following description will be of the preferred arrangement. The lines of demarcation may or may not be present (in whole or in part) on switchgear constructed in accordance with the invention, and the sets may or may not be identical in content or layout, without departing from the scope of the invention. 
       FIG. 3  is a cut-away front elevation view illustrating the preferred layout of a single-phase building block module  600   a  which is composed of a ground switch assembly  200   a , a disconnect switch assembly  300   a , and a vacuum interrupter bottle switch assembly  100   a . For ease of discussion, assemblies  200 ,  300 ,  100  and their components with suffixes “a”, “d”, “g”, or “j” are considered “A Phase”. Assemblies  200 ,  300 ,  100  and its components with suffixes “b”, “e”, “h”, or “k” are considered “B Phase”. Assemblies  200 ,  300 ,  100  and its components with suffixes “c”, “f”, “i”, or “l” are considered “C Phase”. 
     As used herein, the terms “building block” and “building block module” will be used as a convenient short-hand expression to denote a group of components whose configuration is repeated a number of times to form the preferred ground switch assembly. Those of ordinary skill in the art will recognize that the term does not necessarily connote the need for a separate housing for each building block, or the need for a visually identical subassembly from block to block, since the term is used in its conceptual sense only. As will be seen, the preferred embodiment of the invention uses visually identical building blocks within a single housing, but it should be noted that the invention is not limited to that preferred configuration. 
       FIG. 4  is a top view of single-phase building block  600  which illustrates the mechanical and electrical coupling between ground switch assembly  200   a  and disconnect switch assembly  300   a  via connection bus  240   a .  FIG. 4  also illustrates the mechanical and electrical coupling between disconnect assembly  300   a  and vacuum interrupter bottle switch assembly  100   a  via connection bus  140   a.    
     To construct a three-phase building block module  900 , a single-phase building block module  600   b  extends vertically upward and out of cover  12  behind single-phase building block module  600   a  and generally parallel thereto. A single-phase building block module  600   c  extends vertically upward and out of cover  12  behind single-phase building block module  600   b  and generally parallel thereto. This is best illustrated in  FIG. 5  which is a cut-building away top view illustrating the preferred layout of the building blocks  600   a - c  for a three-phase block  900   a . A front elevation view for a three-phase building block  900   a  would be the same as illustrated in  FIG. 3 . For ease of discussion, when two or more three-phase building blocks  900  are referenced in the design, the one designated  900   a  will be considered the “input power” block or “feeder” block and the remaining will be considered as distribution blocks. 
       FIG. 6  is a cut-away right side elevation view of the three-phase building block design  900   a  of  FIG. 3 , illustrating the preferred internal layout of the ground switch assemblies  200   a - c . As illustrated in  FIGS. 3 and 6 , ground switch assembly  200   a - c  is generally comprised of an insulator  202   a - c , an insulating shield  204   a - c , a connector  220   a - c , a top contact  206   a - c , a bottom contact  212   a - c , and a contact rod  208   a - c . Ground switch assembly  200   a  extends vertically upward and out of cover  12 . Ground switch assembly  200   b  extends vertically upward and out of cover  12  behind ground switch assembly  200   a  and generally parallel thereto. Ground switch assembly  200   c  extends vertically upward and out of cover  12  behind ground switch assembly  200   b  and generally parallel thereto. The ground switch assemblies  200   a - c  are connected to a ground bus which in turn is connected to a ground terminal where a ground cable/wire is attached to the switchgear during installation. Grounding occurs when contact rods  208   a - c  are pushed up and into top contacts  206   a - c . Ground switch assemblies  200   a - c  are mechanically and electrically coupled to disconnect switch assemblies  300   a - c  via connection buses  240   a - c  and function to ground the electrical components within the building block design  900   a  so that no residual current remains. 
       FIG. 7  is a cut-away right side elevation view of the three-phase building block design  900   a  of  FIG. 3 , illustrating the preferred internal layout of the disconnect switch assemblies  300   a - c . As illustrated in  FIGS. 3 and 7 , disconnect switch assembly  300   a - c  is generally comprised of a power bushing  302   a - c , an insulating shield  304   a - c , a transparent insulating shield  318   a - c , a connector  320   a - c , top contact  306   a - c  and bottom contact  312   a - c , a contact rod  308   a - c , an insulating shield  314   a - c , and a push-pull insulator  316   a - c . Disconnect switch assembly  300   a  extends vertically upward and out of cover  12 . Although, for reasons that will be understood by those of ordinary skill in the art, the disconnect switch can be made without a transparent insulating shield, the preferred embodiment utilizes one for increased safety purposes. 
     Disconnect switch assembly  300   b  extends vertically upward and out of cover  12  behind disconnect switch assembly  300   a  and generally parallel thereto. Disconnect switch assembly  300   c  extends vertically upward and out of cover  12  behind disconnect switch assembly  300   b  and generally parallel thereto. Disconnect switch assemblies  300   a - c  function to allow power to either enter or exit each building block design  900   a . Besides being connected to ground switch assemblies  200   a - c , disconnect switch assemblies  300   a - c  are also mechanically and electrically coupled to vacuum interrupter bottle switch assemblies  100   a - c  via connection buses  140   a - c . 
       FIG. 8  is a cut-away right side elevation view of the three-phase building block design  900   a  of  FIG. 3 , illustrating the preferred internal layout of the preferred vacuum interrupter bottle switch assemblies  100   a - c . As illustrated in  FIGS. 3 and 8 , vacuum interrupter bottle switch assembly  100   a - c  is generally comprised of a mounting insulator  102   a - c , an insulation shield  104   a - c , a top connector  130   a - c , a vacuum interrupter bottle switch  108   a - c , a common bus connector  110   a - c , an insulation shield  134   a - c , a push-pull insulator  116   a - c , and an operating mechanism assembly  150   a - c . Vacuum interrupter bottle switch assembly  100   a  extends vertically upward and out of cover  12 . Vacuum interrupter bottle switch assembly  100   b  extends vertically upward and out of cover  12 , behind vacuum interrupter bottle switch assembly  100   a  and generally parallel thereto. Vacuum interrupter bottle switch assembly  100   c  extends vertically upward and out of cover  12 , behind vacuum interrupter bottle switch assembly  100   b  and generally parallel thereto. Vacuum interrupter bottle switch assemblies  100   a - c  function to connect power to or break load from three-phase building block designs  900  which are connected to  900   a  via connection buses  145 . 
       FIG. 9  is a cut-away front elevation view of a preferred design for a three-phase, two-way submersible loadbreak vacuum interrupter switchgear with internal ground switch based on the current invention. This preferred design uses only one three-phase building block  900   a  comprised of ground switch assembly  200   a - c , disconnect switch assembly  300   a - c , and vacuum interrupter bottle switch assembly  100   a - c . Mounting insulator  102   a - c  of vacuum interrupter bottle switch assembly  100   a - c  is replaced with a power bushing  103   a - c . This is the preferred design and results in a compact switchgear. A three-phase, two-way submersible loadbreak vacuum interrupter switchgear can be constructed using two three-phase building blocks  900 , but would be twice the size of the preferred design. Bushing wells can also be used instead of power bushings; however, the preferred modification is to use power bushings. 
     When expanding to a three-phase, three-way submersible loadbreak vacuum interrupter switchgear with internal ground switch as illustrated in  FIG. 10 , building block modules  900   a ,  900   b , and  900   c  are positioned staggered to one another as best illustrated in  FIG. 11 . Referring to  FIGS. 10 and 11 , each phase (A, B, and C) is electrically coupled in series with connection buses  145 . A-Phase building block  600   a  is coupled mechanically and electrically to A-Phase building block  600   d  with connection bus  145   a  at vacuum interrupter bottle assembly connector  130   a  and  130   d , respectively. A-Phase building block  600   d  is coupled mechanically and electrically to A-Phase building block  600   g  with connection bus  145   d  at vacuum interrupter bottle assembly connector  130   d  and  130   g , respectively. The same connections are made for B-Phase building blocks  600   beh  via connection buses  145   b  and  145   e  and C-Phase building blocks  600   cfi  via connection buses  145   c  and  145   f.    
       FIG. 12  is a cut-away front elevation view, in schematic, of the preferred switchgear of  FIG. 1 . As illustrated in  FIG. 12 , disconnect switch assemblies  300   a - l  are mechanically and electrically coupled to ground switch assemblies  200   a - l  through connection buses  240   a - l  at connectors  320   a - l  and  220   a - l , respectively. Vacuum interrupter bottle switch assemblies  100   a - l  are mechanically and electrically coupled to disconnect switch assemblies  300   a - l  through connection buses  140   a - l.    
       FIG. 13  is a cut-away top elevation view of the preferred switchgear of  FIG. 1 , in schematic, and best illustrates the internal layout of connection buses  140   a - l ,  240   a - l , and  145   a - i  to the ground switch assemblies  200   a - l , disconnect switch assemblies  300   a - l , and vacuum interrupter bottle switch assemblies  100   a - l . Disconnect switch assemblies  300   a - l  are mechanically and electrically coupled to ground switch assemblies  200   a - l  through connection buses  240   a - l  at connectors  320   a - l  and  220   a - l , respectively. Vacuum interrupter bottle switch assembly  100   a  is mechanically and electrically coupled to vacuum interrupter bottle switch assembly  100   d  through connection buses  145   a  at connectors  130   a  and  130   d , respectively. Vacuum interrupter bottle switch assembly  100   d  is mechanically and electrically coupled to vacuum interrupter bottle switch assembly  100   g  through connection buses  145   d  at connectors  130   d  and  130   g , respectively. Vacuum interrupter bottle switch assembly  100   g  is mechanically and electrically coupled to vacuum interrupter bottle switch assembly  100   j  through connection buses  145   g  at connectors  130   g  and  130   j , respectively. The same connection method is repeated for vacuum interrupter bottle switch assemblies  100   b  to  100   e  to  100   h  to  100   k  at connectors  130   b ,  130   e ,  130   h , and  130   k , respectively, via connection buses  145   b ,  145   e , and  145   h . This connection method is also repeated for vacuum interrupter bottle switch assemblies  100   c  to  100   f  to  100   i  to  100   l  at connectors  130   c ,  130   f ,  130   i , and  130   l , respectively, via connection buses  145   c ,  145   f , and  145   i.    
       FIG. 14  is a front elevation view of the preferred switchgear of  FIG. 1  in schematic, illustrating the viewing windows  55   a - d  and positions of the operating handles of the ground switch, disconnect switch, and vacuum interrupter switch assemblies. All operating handles have “open” and “closed” positions. In the preferred design, the open positions have the operating handles pointed in a downward “8 o&#39;clock” direction. The closed positions have the operating handles pointed in a “10 o&#39;clock” direction. The operating handles rotate in a clockwise direction to change from the open to closed position. The operating handles rotate in a counterclockwise direction to change from the closed to open position. As illustrated in  FIG. 14 , operating handles  521   a - c ,  522   d , and  523   a - c  are in the closed position. Operating handles  521   d ,  522   a - c , and  523   d  are in the open position. As illustrated, when disconnect switch handles  523   a - c  are in the closed position, disconnect contact rods  308   a - c ,  308   d - f ,  308   g - i  can be seen through viewing windows  55   a ,  55   b , and  55   c , respectively. With disconnect switch handle  523   d  in the open position, disconnect contact rods  308   j - l  are not seen in viewing window  55   d . As illustrated, when ground switch handles  522   a - c  are in the open position, ground contact rods  208   a - c ,  208   d - f ,  208   g - i  cannot be seen through viewing windows  55   a ,  55   b , and  55   c , respectively. With ground switch handle  522   d  in the closed position, ground contact rods  208   j - l  are seen in viewing window  55   d . With the handles in the positions illustrated, three-phase building blocks  900   a ,  900   b , and  900   c  are in the closed position and ready for operation. Three-phase building block  900   d  is in the open position, grounded, and not in operation. 
       FIG. 15  is a top elevation view of the described invention and best illustrates the positions of power bushings  302   a - l  of disconnect switch assemblies  300   a - l  and switch status indicators  85   a - l  on cover  12 . Switch status indicators  85   a ,  85   d ,  85   g , and  85   j  show the open or closed status for ground switch assemblies  200   a - c ,  200   d - f ,  200   g - i , and  200   j - l , respectively. Switch status indicators  85   b ,  85   e ,  85   h , and  85   k  show the open or closed status for disconnect switch assemblies  300   a - c ,  300   d - f ,  300   g - i , and  300   j - l , respectively. Switch status indicators  85   c ,  85   f ,  85   i , and  85   l  show the open or closed status for vacuum interrupter bottle switch assemblies  100   a - c ,  100   d - f ,  100   g - i , and  100   j - l , respectively. These indicators show switch status to an operator who is viewing the switchgear from above. 
       FIGS. 16 and 17  are front and top elevation view, respectively, in schematic, of the three-phase, four-way submersible loadbreak vacuum interrupter switchgear with internal ground switch of  FIG. 14 , illustrating the attachment of power cables onto power bushings  302   a - l  which provide power to the switchgear and out to branch circuits. Any ABC set of power cables can be used as the incoming three-phase power feeder with the remaining sets used to distribute three-phase power to branch circuits. 
     Referencing  FIGS. 12 and 13 , the electrical flow will be described using three-phase building block  900   a  as the power input and three-phase building blocks  900   b ,  900   c , and  900   d  as the power outputs for distribution to the branch circuits. As shown in  FIGS. 12 ,  900   a ,  900   b , and  900   c  are in the closed position and  900   d  is in the open position. Electricity enters  900   a  through power bushings  302   a - c  and into vacuum interrupter bottle assemblies  100   a - c  though connection bus  145   a - c . The electricity travels to  900   b ,  900   c , and then  900   d  through connection buses  145   a - c ,  145   d - f , and  145   g - i , respectively. In  900   b  and  900   c , electricity passes through vacuum interrupter bottles  108   d - f  and  108   g - i  and out through disconnect switch assemblies  302   d - f  and  302   g - i  via connection buses  145   d - f  and  145   g - i , respectively. Electricity does not pass through  900   d  since vacuum interrupter bottles  108   j - l  are open. 
     Interlocking operating mechanisms are utilized to ensure proper operating procedures when switch assemblies within the switchgear are opened or closed. Referring initially to  FIG. 1 , operating handles  521   a ,  522   a  and  523   a  have previously been described as having “open” and “closed” positions wherein the open positions preferably have the operating handles pointed in a downward “8 o&#39;clock” direction, while the closed positions have the operating handles pointed in a “10 o&#39;clock” direction, with the operating handles being rotated in a clockwise direction to change from the open to closed position and in a counterclockwise direction to change from the closed to open position. 
     Operating handles  522   a ,  523   a  and  521   a  are operatively coupled to the ground switch assembly, vacuum bottle switch assembly, disconnect switch assembly and vacuum bottle switch assembly, respectively, of block  900   a . Likewise,  522   b ,  523   b  and  521   b  are operatively coupled to the ground switch assembly, vacuum bottle switch assembly, disconnect switch assembly and vacuum bottle switch assembly, respectively, of block  900   b , etc.  FIG. 18A  schematically illustrates the positions of the operating handles at the front  11   b  of the switchgear case  10  when the block  900   a ,  900   b ,  900   c ,  900   d  is non-conducting, as it would be prior to access for maintenance or during installation and set-up. Since the position and operation of corresponding operating handles is the same from block to block, the letter suffix of each numeric identifier is omitted for brevity. 
     With the handle  522  in its “closed” 10 o&#39;clock position, the ground switch assembly is closed in order to shunt any residual current to ground. Disconnect switch handle  523  and vacuum bottle switch handle  521  are both in the “open” 8 o&#39;clock position, and the switch assemblies to which they are linked are accordingly in their open-circuit positions. 
       FIG. 18B  schematically illustrates the relevant linkages behind the front  11   b  of the switchgear case  10  for the handle positions of  FIG. 18A . Ground switch handle  522  rotates about axis  524  as illustrated in  FIG. 18A , and  FIG. 18B  illustrates a clevis  525  that rotates about axis  524  on the back side of front surface  11   b  in response to the handle rotation. 
     Likewise, a clevis  527  ( FIG. 18B ) rotates about axis  526  when the disconnect switch handle  523  ( FIG. 18A ) rotates about axis  526 . A pin  527   a , however, extends from disconnect switch clevis  527  to contact ground switch clevis  525  in such a way, when the handles are in the illustrated position, that disconnect switch handle  523  is prevented from rotating into its “closed” position when the ground switch handle is in its closed position and the ground switch assemble is thereby closed. Similarly, a pin  529   a  extends from a clevis  529  coupled to the vacuum bottle switch handle  521  for rotation therewith around axis  528 , so as to contact disconnect switch clevis  527  and prevent the vacuum switch handle  521  from being rotated to its “closed” position (to thereby close the vacuum bottle switch) when the disconnect switch handle is in its “open” position. Thus, it is not possible to close the disconnect switch or the vacuum bottle switch when the ground switch is closed, and no current can accidentally be permitted to flow into and through the block and be short-circuited to ground. Such a short circuit could result in a huge and dangerous current flow. Similarly, it is not possible to close the disconnect switch assemblies after the vacuum switch assemblies have been closed, or to open the disconnect switch assemblies while the vacuum switch assemblies are closed, thereby preventing arcing across the electrical contacts of the disconnect switches that might occur if the disconnect switch assemblies were switching power current on or off in an otherwise completed circuit. Consequently, such switching occurs within the relatively safe confines of the vacuum bottle switch assemblies. 
     Turning to  FIGS. 18C and 18D , the ground circuit handle  522  has been moved to its “open” 8 o&#39;clock position, thereby rotating clevis  524  away from pin  527   a . With the ground switch assembly now open, the disconnect assembly switch can be safely closed, as illustrated next in  FIGS. 18E-F . With disconnect switch handle rotated into its “closed” 10 o&#39;clock position, disconnect switch clevis  527  is rotated away from pin  529   a  to thereby permit rotation of vacuum bottle switch clevis. 
     As next illustrated in  FIGS. 18H-G , the rotation of the vacuum bottle switch handle to its “closed” 10 o&#39;clock position, and the consequential rotation of its clevis  529 , causes pin  529   a  to once again contact disconnect switch clevis  527  in such a way that the disconnect switch handle cannot be rotated to its “open” position while the vacuum bottle switch is closed. 
     As a result of all of the foregoing, the only way the block  900  can be open circuited is the safest way: its vacuum bottle switch, followed by its disconnect switch, followed by the closing of its ground switch. Conversely, the block can only be activated the safest way: opening the ground switch, followed by closing the disconnect switch, followed by closing the vacuum bottle switch. In addition, the rods of the ground switch and disconnect switch are visible through the viewing window  55  when the respective switch is closed for visual confirmation of same. 
     Because the state of the vacuum bottle switch assembly prevents the disconnect switch assembly from making or breaking an active circuit, no arcing can occur across the electrical contacts of the disconnect switch; accordingly, the transparent shield is not mandatory, but is highly preferred as a safety precaution in any event. The ground switch assemblies, on the other hand, do not need transparent insulating shields in the preferred embodiment because the contact rod is permanently connected to ground. 
     Those skilled in the art will recognize that other type of shaft movement may be utilized besides shaft rotation as described above. For example, the mechanisms can be configured to permit one or more of the handles of each building block to be pushed or pulled to thereby selectively engage more than one driven clevis with a single handle-driven shaft. Similarly, structures other than a clevis can be used, and a structure other than a pin can provide blocking. This is all within the knowledge and ability of mechanical designers, and within the scope of the invention. 
     Further, it may be desirable to replace each of the illustrated viewing windows  55  with two smaller windows that are each sized and positioned to permit the view of only a respective one of the two rods. This alternative configuration may better focus the attention of installation and maintenance personnel on the presence or absence of an expected rod since the presence or absence of the rod will be more apparent with a narrowed more targeted view for a single item. 
     Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention defined by the appended claims.