Patent Publication Number: US-9892875-B2

Title: Gas circuit breaker

Description:
TECHNICAL FIELD 
     The present invention relates to a gas circuit breaker for the power having an extinguishing gas, and particularly relates to an exhaust structure on a movable side of a circuit breaker part. 
     BACKGROUND ART 
     In recent years, the capacity of a circuit breaker is increased as voltage/current of a power system is increased, but a request for reducing cost and space by optimizing the structure of the circuit breaker part is increased, and it is required to secure excellent circuit-breaking performance with a lower operating force. 
     Gas circuit breakers including a thermal puffer type circuit breaker generally includes a puffer shaft connecting a movable-side circuit breaker part formed of a puffer cylinder, an insulating nozzle, a movable main contact and a movable arc contact to an insulating rod, and a gas passage is provided inside the puffer shaft. 
     The gas passage is provided for the purpose of spraying an extinguishing gas compressed in the puffer cylinder on the arc generated between the movable arc contact and a stationary arc contact, then, exhausting the gas to the movable side of the circuit breaker part. 
     The extinguishing gas passing through the gas passage of the puffer shaft is heated by the arc and contacts particles of a nozzle material and an electrode material melted by the arc, therefore, the gas has a high temperature and is contaminated. Due to the extinguishing gas with the high temperature (hereinafter referred to as a hot gas), the surface of the insulating rod or the inside of an insulation cylinder may be burned and carbonized, or conductive foreign substances may stick, which may drastically reduce the insulation performance and may cause a ground fault. 
     In Patent Literature 1, there is disclosed a gas circuit breaker including a puffer shaft coupled to an insulation rod side through a shaft guide and an exhaust cylinder provided inside a movable-side main circuit conductor so as to surround the insulation rod, in which a piston ring provided in an outer periphery of the shaft guide slides inside the exhaust cylinder. The invention contributes to the improvement in insulation performance of the gas circuit breaker by blocking a flow path through which the hot gas flows toward the insulation rod and the insulation cylinder. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP-A 2013-125720 
     SUMMARY OF INVENTION 
     Technical Problem 
     As a gap between the exhaust cylinder and the shaft guide is completely blocked with the piston ring in the gas circuit breaker disclosed in Patent Literature 1, the piston ring slides while directly contacting an inner surface of the exhaust cylinder, therefore, slight sliding resistance is generated. Moreover, as the shaft guide has an outer diameter which is approximately equal to an inner diameter of the exhaust cylinder, a certain degree of size and rigidity may be necessary. An object of the present invention is to provide a gas circuit breaker capable of protecting the insulation rod and the insulation cylinder from the hot gas, improving the insulation performance and realizing smooth breaking operation with a lighter and simpler structure. 
     Solution to Problem 
     According to an embodiment of the present invention, there is provided a gas circuit breaker having an insulation tank filled with an extinguishing gas, a pair of a stationary-side main circuit conductor and a movable-side main circuit conductor provided in insulation tank, a stationary-side contact and a movable-side contact provided between the stationary-side main circuit conductor and the movable-side main circuit conductor so as to be separated, a puffer cylinder having the movable-side contact at one end, a puffer chamber formed in the puffer cylinder, an insulation nozzle forming a flow path for leading the extinguishing gas in the puffer chamber to arc generated between the movable-side contact and the stationary-side contact, a puffer shaft having a gas passage for leading the extinguishing gas led to the arc to the movable side of a circuit breaker part and exhausting the gas, and an insulation rod coupled to the puffer shaft, which includes a hot gas blocking member at a joint between the puffer shaft and the insulation rod. 
     Advantageous Effects of Invention 
     According to the present invention, the improvement in insulation performance and circuit-breaking performance of the gas circuit breaker can be realized with a simple structure 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a cross-sectional view of an input state of a gas circuit breaker to which a movable-side exhaust structure according to Example 1 is applied. 
         FIG. 2  is an enlarge view of an insulation rod cover portion according to Example 1. 
         FIG. 3  is a cross-sectional view of a circuit-breaking process (intermediate position) of the gas circuit breaker to which the movable-side exhaust structure according to Example 1 is applied. 
         FIG. 4  is a cross-sectional view of a circuit-breaking process (circuit-breaking position) to which the movable-side exhaust structure according to Example 1 is applied. 
         FIG. 5  is a cross-sectional view of a gas circuit breaker to which a movable-side exhaust structure according to Example 2 is applied. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be explained with reference to the drawings. The following are lust examples and do not intend to limit the contents of the invention to the following specific examples. The invention itself may be achieved in various manners in conformity with the contents described in claims. 
     Example 1 
       FIG. 1  is a schematic view of an inside of a gas circuit breaker formed by using an exhaust structure according to the present invention. Structures other than the exhaust structure are the same as structures of a related-art puffer-type gas circuit breaker. 
     An extinguishing gas such as an SF 6  gas is sealed in an insulation tank  1 , and a stationary-side live conductor  11  and a movable-side live conductor  21  are drawn into the tank. 
     The stationary-side live conductor  11  is electrically connected to a stationary-side main circuit conductor  12 , a stationary arc contact base  13 , a stationary arc contact  14  and a stationary main contact  15  which configure a stationary-side circuit breaker part  10 . 
     The movable-side live conductor  21  is electrically connected to a circuit-breaker part movable portion  30  through a movable-side main circuit conductor  22 , a sliding contact  23  and a puffer cylinder  31 . 
     A stationary piston is disposed inside the movable-side main circuit conductor  22 , and an inner cylinder surface of the puffer cylinder  31  is supported by a puffer cylinder supporting sliding guide  25  attached to an outer periphery of the stationary piston  24 . The sliding contact  23  is provided in an inner periphery of the movable-side main circuit conductor  22 , which contact an outer cylinder surface of the puffer cylinder  31 . According to the structure, the puffer cylinder  31  can move in an axial direction while maintaining electrical connection through the movable-side main circuit conductor  22  and the sliding contact  23 . 
     A through hole is provided in the center of the stationary piston  24 , and a puffer shaft  32  having a gas passage  41  thereinside is disposed inside the stationary piston  24  so as to slide freely. The puffer shaft  32  is supported by a puffer-shaft supporting sliding guide  26  attached in an inner periphery of the stationary piston  24 . 
     One end of the puffer shaft  32  is fixed to the puffer cylinder  31  and the other end of the puffer shaft  32  is coupled to one end of an insulation rod  34  through a circuit-breaker side coupling pin  33 . The other side of the insulation rod  34  is coupled to a lever  36  housed in a mechanism case  2  provided adjacent to the insulation tank  1  through a lever-side coupling pin  35 . 
     A shaft  37  of the lever  36  is supported by the mechanism case  2  so as to rotate freely. The lever  36  is connected to an actuator (not shown) on the outside of the mechanism case  2  through the shaft  37 . The lever  36  rotates by a drive force of the actuator, and the circuit breaker part movable portion  30  moves in the axial direction. 
     A movable arc contact  51  is provided in the center of a tip portion of the puffer cylinder  31 . An insulation cover  52 , an insulation nozzle  53  and a movable main contact  54  are respectively arranged in a concentric manner so as to surround an outer periphery of the movable arc contact  51 . 
     The movable arc contact.  51  has a through hole, which is connected to the gas passage  41  inside the puffer shaft  32  through the puffer cylinder  31 . The gas passage  41  of the puffer shaft  32  extends to the vicinity of a joint between the puffer shaft  32  and the insulation rod  34 , opening at an opening A  42  on a cylinder surface of the puffer shaft  32  in a radial direction. 
     The movable-side main circuit conductor  22  is supported by an insulation cylinder  27  fixed to the insulation tank  1 . The movable-side main circuit conductor  22  has an opening B  43  on a side surface, which communicates into the insulation tank  1 . The movable-side main circuit conductor  22  has a guard cylinder  29  thereinside close to the insulating cylinder  27  and an exhaust cylinder  28  close to the stationary piston  24 . The guard cylinder  29  and the exhaust cylinder  28  are fixed to an inner wall of the movable-side main circuit conductor  22  and the stationary piston  24  by means of, for example, bolt fastening. 
     The insulation rod  34  is disposed inside the exhaust cylinder  28 , the guard cylinder  29  and the insulation cylinder  27  so as to move freely in the axial direction. The joint between the puffer shaft  32  and the insulation rod  34  housed inside the exhaust cylinder  28  is covered with an insulation rod cover  38 . 
       FIG. 2  shows a structure of the joint between the puffer shaft  32  and the insulation rod  34 . 
     A pin portion  61  of the circuit-breaker side coupling pin  33  penetrates through a pin hole of the puffer shaft  32  and a pin hole of the insulation rod  34 , and the puffer shaft  32  and the insulation rod  34  are coupled so as to rotate freely around an axis of the circuit-breaker side coupling pin  33 . 
     The circuit-breaker side coupling pin  33  is formed of a female screw component  63  and a male screw component  64 . The female screw component  63  includes an insulation rod cover support portion A  62  and the pin portion  61  having a female screw portion. The male screw component  64  includes an insulation rod cover support portion B  65  and a male screw portion. The circuit-breaker side coupling pin  33  has a structure in which the female screw component  63  is combined with the males screw component  64  by screwing and so on, which can be assembled and disassembled from both sides of the pin hole. In the description, the combined structure is referred to as a divided structure. 
     The insulation rod cover  38  is a cylindrical member having a size to be housed inside the exhaust cylinder  28  and the guard cylinder  29 , which is made of PTFE (polytetrafluoroethylene). Materials other than PTFE may be used as long as materials have excellent heat durability and mechanical strength and are light in weight. 
     An end portion of the puffer shaft  32  is fitted to the insulating rod cover  38 . On an outer cylinder surface of insulating rod cover  38 , there is formed a through hole a diameter of which is slightly larger than the insulation rod cover support portion A  62  and the insulation rod cover support portion B  65  of the circuit-breaker side coupling pin  33 . As the insulation rod cover support portion A  62  and the insulation rod cover support portion B  65  of the circuit-breaker side coupling pin  33  are fitted to the through hole, the insulating rod cover  38  is held by the circuit-breaker side coupling pin  33 . That is, the insulating rod cover  38  is held by the end portion of the puffer shaft  32  and the circuit-breaker side coupling pin  33  so as to cover the joint between the puffer shaft  32  and the insulation rod  34 . 
     As the structure of covering the joint is adopted as described above, it is possible to prevent foreign substances carried by a hot gas from sticking to the joint between the puffer shaft  32  and the insulation rod  34 , therefore, a later-described vertical motion of the insulation rod  34  can be maintained to be smooth. 
     Moreover, as the structure of holding the insulation rod cover is adopted as described above, it is possible to prevent the insulation rod cover from falling off due to an impact of a circuit-breaking operation. Therefore, the reliability of the circuit breaker can be improved. 
     The structure of the insulation rod cover  38  is an example of the member for blocking the hot gas. The structure in which foreign substances carried by the hot gas can be prevented from sticking to the joint between the puffer shaft  32  and the insulation rod  34  as well as the insulation rod cover can be prevented from falling off can be applied to the circuit breaker according to the present invention, not being limited to the above insulation rod cover  38 . 
     The insulation rod cover  38  moves along inner surfaces of the exhaust cylinder  28  and the guard cylinder  29  with the circuit-breaker side coupling pin  33  when the circuit breaker part movable portion  30  moves. When the drive force of the actuator (not shown) is transmitted to the lever  36  through the shaft  37  and the lever  36  moves in an arc, the insulation rod  34  vertically moves slightly with the circuit-breaker side coupling pin  33  as a fulcrum. An inner diameter of the opening of the insulation rod cover  38  on the side not fitted to the puffer shaft  32  is formed to be a size not interfering with the exhaust cylinder  28  and the guard cylinder  29  even when the insulation rod  34  vertically moves. 
     It is preferable to form the fitted portion between the insulation rod cover  38  and the puffer shaft  32  with a gap as small as possible for preventing the infiltration of the hot gas from the circuit breaker part. 
     The structure of the embodiment will be explained based on the circuit-breaking operation.  FIG. 1  shows an input state of the gas circuit breaker, in which the movable main contact  54  is inserted into the stationary main contact  15 , and the circuit breaker part movable portion  30  and the stationary-side circuit breaker part  10  are electrically connected completely. 
     In this state, the inside of a throat portion  45  as the minimum diameter portion of the insulation nozzle  53  and the movable arc contact  51  is almost blocked by the stationary arc contact  14 , and the opening A  42  of the puffer shaft  32  is closed as it is positioned inside the stationary piston  24 . The insulation rod cover  38  is also housed inside the exhaust cylinder  28 . 
     When the circuit breaker part movable portion  30  moves to the movable side by the circuit-breaking operation from the state shown in  FIG. 1 , the movable arc contact  51  is separated from the stationary arc contact  14 . In the case where a large electric current flows between the circuit breaker part movable portion  30  and the stationary-side circuit breaker part  10  in the above state, the electric current is not interrupted even when the movable arc contact  51  is separated from the stationary arc contact  14 , and the arc is generated between the movable arc contact  51  and the stationary arc contact  14 , therefore, the electric current continues flowing. 
     When the circuit-breaking operation proceeds after the movable arc contact  51  and the stationary arc contact  14  are separated to be a state shown in  FIG. 3 , the throat portion  45  is almost blocked by the stationary arc contact  14 , but the end portion of the circuit breaker part movable portion  30  on the actuator&#39;s side is opened as the opening A  42  moves to a space D  46  formed between the exhaust cylinder  28  and the insulation rod cover  38 . Accordingly, the flow of the hot gas exhausted to the movable-side main circuit conductor  22  through the gas passage  41  inside the puffer shaft  32  is formed. 
     In the structure of the embodiment, the hot gas exhausted from the opening A  42  of the puffer shaft  32  is first released to the space D  46  formed by the exhaust cylinder  28  and the insulation rod cover  38 . The hot gas exhausted from the opening A  42  has a high temperature and contains particles of a nozzle material or an electrode material melted by the arc. 
     The insulation rod  34  is generally formed of a GFRP (glass fiber reinforced plastic) coated with an extinguishing-gas resistance film. When the hot gas is directly sprayed on the insulation rod  34 , the coating on the surface may be burned and the insulation performance may be reduced. Moreover, when particles of the electrode material and so on contained in the hot gas are fused into a slight gap existing between the circuit-breaker side coupling pin  33  and the insulation rod  34  as well as between the lever-side coupling pin  35  and the insulation rod  34 , the smooth circuit-breaking operation may be inhibited. 
     The gas circuit breaker according to the embodiment can prevent the reduction of the insulation performance in the insulation rod  34  as it is possible to prevent the hot gas from being directly sprayed onto the insulation rod  34  due to the insulation rod cover  38 . It is also possible to prevent the above-described particles from sticking to the joint portion between the insulation rod  34  and the puffer shaft  32 , therefore, the smooth circuit-breaking operation can be realized. 
     On the other hand, the structure of the present invention including the exhaust cylinder  28 , the insulation rod cover  38  and the guard cylinder  29  also contributes to the improvement in circuit-breaking performance as described below. 
     As shown in  FIG. 3 , the hot gas released to the space  46  passes through a gap E  47  between the exhaust cylinder  28  and the insulation rod cover  38  and flows to the downstream side of the circuit breaker part, namely, to the outside of the exhaust cylinder  28 . When the cross-sectional area of the gap F  47  is sufficiently small with respect to the cross-sectional area of the space D  46 , there are advantages that the exhaust of the hot gas from the gas passage  41  is suppressed and the pressure inside the puffer cylinder  31  is increased. The increase of the pressure inside the puffer cylinder  31  at the time of staring the circuit-breaking operation leads to the improvement in circuit-breaking performance. 
     As the circuit-breaking operation further proceeds and the stationary arc contact  14  comes off from the throat portion  45 , or the gap E  47  becomes sufficiently large as shown in  FIG. 4 , the hot gas passes through the throat portion  45  and flows to the stationary arc contact  14 , therefore, two flow paths of the hot gas divided into the stationary side and the movable side are formed. 
     In the state shown in  FIG. 4 , the gas released from the opening A  42  is released into the movable-side main circuit conductor  22  and is exhausted from the opening B  43  of the movable-side main circuit conductor  22 . The flow of the extinguishing gas which is not suppressed is formed as an exit of the space D  46  is not blocked by the insulation rod cover  38 , therefore, the hot gas generated by arc is smoothly exhausted and the cooling of the movable arc contact  51  is also promoted. 
     In the structure of the embodiment, the insulation rod cover  38  moves to the inside of the guard cylinder  29  in a last half of the circuit-breaking operation. As the area of a gap F  48  between the guard cylinder  29  and the insulation rod cover  38  is sufficiently smaller than the area of the opening B  43 , she flow path resistance is high and the flowing of the hot gas into the insulation cylinder  27  can be suppressed. Accordingly, it is possible to prevent the insulation rod  34  and the insulation cylinder  27  from being contaminated by the hot gas, therefore, the reduction in the insulation performance can be prevented. 
     In the description, while the stationary arc contact  14  moves in the throat portion  45  of the insulation nozzle  53  from the start of the circuit-breaking operation (namely, a period of the circuit-breaking operation in which the pressure of the extinguishing gas inside the puffer cylinder  31  is increased) is defined as a first half of a circuit-breaking operation. A period in which the circuit-breaking operation is completed after the stationary arc contact  14  comes off from the throat portion  45  of the insulation nozzle  53  is defined as a last half of a circuit-breaking operation. 
     Example 2 
     Another embodiment of the present invention will be explained with reference to  FIG. 5 . The same numerals are given to the same components as those of Example 1 and the explanation is omitted. 
     In Example 2, the exhaust cylinder  28  is extended so that a length of a gap between the exhaust cylinder  28  and the guard cylinder  29  is approximately equal to a length of the insulation rod cover  38  in the axial direction, and an exhaust hole C  44  is provided on a side surface of the exhaust cylinder  28 . 
     In the structure in which the exhaust cylinder  28  is extended as shown in  FIG. 5 , the insulation rod cover  38  enters the inside of the guard cylinder  29  just after the insulating rod cover  38  comes off from the exhaust cylinder  28 , therefore, the flow of the hot gas toward the insulation cylinder  27  can be blocked. Accordingly, the reduction in the insulation performance of the insulation cylinder  27  and the insulation rod  34  can be prevented. 
     When the exhaust cylinder  28  is simply extended, the hot gas accumulated in the space D  46  inside the exhaust cylinder  28  is not released and there is a risk that the temperature inside the exhaust cylinder  28  is drastically increased and the circuit-breaking performance is reduced. In response to this, the exhaust hole C  44  is provided on the side surface of the exhaust cylinder  28  and the hot gas accumulated in the space D  46  inside the exhaust cylinder  28  is released from the exhaust hole C  44  on the side surface during the circuit breaking operation, thereby preventing the reduction of the circuit-breaking performance. 
     The above explanation has been made by citing the machine-puffer type as circuit breaker as an example, however, the present invention can be naturally applied to dual-chamber puffer type gas circuit breaker, and the above advantages can be obtained also when the present invention is applied to the dual-chamber puffer type gas circuit breaker. 
     REFERENCE SIGNS LIST 
     
         
           1  insulation tank 
           2  mechanism case 
           10  stationary-side circuit breaker part 
           11  stationary-side live conductor 
           12  stationary-side main circuit conductor 
           13  stationary arc contact base 
           14  stationary arc contact 
           15  stationary main contact 
           21  movable-side live conductor 
           22  movable-side main circuit conductor 
           23  sliding contact 
           24  stationary piston 
           25  puffer cylinder supporting sliding guide 
           26  puffer-shaft supporting sliding guide 
           27  insulation cylinder 
           28  exhaust cylinder 
           29  guard cylinder 
           30  circuit breaker part movable portion 
           31  puffer cylinder 
           32  puffer shaft 
           33  circuit-breaker side coupling pin. 
           34  insulation rod 
           35  lever-side coupling pin 
           36  lever 
           37  shaft 
           38  insulation rod cover 
           41  gas passage 
           42  opening A 
           43  opening B 
           44  exhaust hole C 
           45  throat portion 
           46  space D 
           47  gap  3   
           48  gap F 
           51  movable arc contact 
           52  insulation cover 
           53  insulation nozzle 
           54  movable main contact 
           61  pin portion 
           62  insulation rod cover support portion A 
           63  female screw component 
           64  male screw component 
           65  insulation rod cover support portion B