Abstract:
In a gas-insulated switching device capable of reducing the physical installation space while suppressing the installation height of the device, busbar connecting lines are disposed perpendicularly to and between as pair of main busbars to connect the main busbars. Three sets (one set per phase) of three serially connected horizontal broker units are placed in parallel, and each of the main busbars has three busbar units along a portion extending vertically from the end of the busbar connecting line.

Description:
FIELD OF INVENTION 
     The present invention relates to a gas-insulated switching device for an electric station such as a power plant and a switching station. 
     BACKGROUND OF THE INVENTION 
     A well-known conventional gas-insulated switching apparatus is disclosed by Japanese Utility Model Right Publication No. H 03-39310 (1991). This gas-insulated switching apparatus is of a 1+½-switch arrangement in which oppositely-disposed parallel busbar connecting lines are arranged perpendicularly to the busbars. Busbar units of three phases constituting the main busbars are arranged almost in parallel in the side outer than the ends of the connecting lines. 
     To reduce the installation space of said gas-insulated switching device, for example, Japanese Application Patent Laid-Open Publication No. Hei 08-47125 discloses a vertically-placed breaker units which constitute the connecting lines. However, this configuration makes the gas-insulated switching device taller but less earthquake-resistant. Therefore, the gas-insulated switching device of this type may not be installed in a height-limited location. In other words, the gas-insulated switching device of this type is not available to an indoor plant or an underground substation. 
     SUMMARY OF THE INVENTION 
     A representative object of the present invention is to reduce the installation space without increasing its height. 
     The basic features of the present invention are that three horizontal breaker units are connected in series by the connecting lines each of which is disposed perpendicularly to the main oppositely-disposed busbars and that each of the mains has busbar units of three phases along a portion (stud) rising from the end of each busbar connecting line. 
     In the description of the present invention, the end of each busbar connecting line means the end of a circuit block near the main busbar in the breaker units which are located at both ends of the busbar connecting line. More concretely, it means the end of the enclosure of an airtight container constituting the power breaker block towards the main busbar. The horizontal power breaker unit is a power breaker unit whose airtight container constituting the power breaker block is placed horizontally, that is, the central axis of the airtight container is horizontal and electric contacts in the airtight container are horizontally separated. 
     The stud rising from the end of the busbar connecting line comprises a busbar connecting unit and is connected to the enclosure of the airtight container facing to the busbar. The busbar unit constituting the main busbar is placed oppositely to the main busbar of the busbar connecting unit or in the side of the main busbar connecting unit. A plurality of busbar connecting lines can be placed along the main busbar. 
     The present invention can suppress the physical height of the gas-insulated switching device as the busbar connecting lines are constituted by horizontal power breaker units. Further, the disposition of the busbar units along the studs which rise from the end of the busbar connecting lines can reduce the dimensions perpendicular to the main busbars of the gas-insulated switching device and consequently the installation space of the gas-insulated switching device. 
     For connection of the adjacent power breaker units, parts stand upright from the ends of the power breaker units. In other words, power breaker units are connected by a breaker connecting unit which comprises two vertical parts rising from the ends of the adjacent power breaker units and a horizontal part connecting these vertical parts. “The end of a power breaker unit” means the end of the enclosure of the airtight container constituting the breaker block of the power breaker unit. Further, “the adjacent power breaker units” means the adjoining two of three power breaker units which are connected in series. 
     In accordance with the present invention, the power breaker units are connected by means which rise upright from the end of the breaker units. In other words, the power breaker units are connected by a breaker connecting unit comprising vertical and horizontal units. Therefore, the distance between the adjacent power breaker units can be reduced. This can further reduce the installation space of the gas-insulated switching device. 
     Basically, a line leader line is vertically connected to a part (or a breaker connecting unit) between the adjacent power breaker units. Only one leader line is connected to one breaker connecting unit. In some cases (particularly when the leader line comprises a main and auxiliary lines), two leader lines can be connected thereto. In such a case, one of the vertically drawn-out leader lines is drawn out horizontally so as to be perpendicular to the other leader line. Or one of two leader lines is drawn out between respective busbar connecting lines. For example, one of the leader lines  35  for the first phase is drawn to a place between the first and second phases and one of the leader lines for the second and third phases are drawn to places between the second and third phases. There are two ways of drawing one of two leader lines away from the other leader line: drawing the leader line slantwise along the main busbar and drawing the leader line in parallel to the man busbar and then towards (perpendicular to) the main busbar. 
     In accordance with the present invention, when two leader lines are simultaneously drawn from the adjacent power breaker units or a breaker connecting unit, one of two vertically-drawn leader lines is drawn horizontally away from the other leader line or horizontally to a place between phases of the busbar connecting lines. Therefore, two leader lines can be simultaneously drawn from between the adjacent power breaker units. This can reduce the distance between two opposite busbars of the gas-insulated switching device. 
     Further, a transformer unit is connected to a portion between the adjacent power breaker units, or the stud of the breaker connecting units. To suppress the power breaker unit from increasing the physical height of the gas-insulated switching device, this invention disposes the transformer unit in a space between two studs on the ends of the enclosure of the airtight container which constitutes the breaker unit of the power breaker unit. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a plan view of the layout of components of a gas-insulated switching device which is a first embodiment of the present invention. 
     FIG. 2 is a plan view taken on line II—II of FIG.  1 . 
     FIG. 3 is a plan view taken on line III—III of FIG.  1 . 
     FIG. 4 is a plan view taken on line IV—IV of FIG.  1 . 
     FIG. 5 is a single connection diagram of a gas-insulated switching device of FIG.  1 . 
     FIG. 6 is a plan view of the component layout of a gas-insulated switching device which is a second embodiment of the present invention. 
     FIG. 7 is a plan view taken on line VII—VII of FIG.  6 . 
     FIG. 8 is a plan view taken on line VIII—VIII of FIG.  6 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     (Embodiment 1) 
     Referring to FIG. 1 to FIG. 5, the first embodiment of the present invention will be explained below. FIG. 5 shows a schematic diagram of a gas-insulated switching device which is a first embodiment of the present invention. This embodiment is of a 1+½-switch arrangement. The main busbars  1  and  2  dual busbars are connected with busbar connecting lines  3   a  to  3   c . These lines  3   a  to  3   c  consist of serially-connected unit lines  4   a  to  4   c.    
     The unit line  4   a  comprises a breaker  5   a  having a transformer  6   a , a disconnecting switch  8   a , and a rounding switch  9   a  at one end of the breaker  5   a  and a current transformer  7   a , a disconnecting switch  10   a , and a grounding switch  11   a  at the other end of the breaker  5   a . The unit line  4   b  comprises a breaker  5   b  having a transformer  6   b , a disconnecting switch  8   b , and a grounding switch  9   b  at one end of the breaker  5   b  and a current transformer  7   b , a disconnecting switch  10   b , and a rounding switch  11   b  at the other end of the breaker  5   b.    
     The unit line  4   c  comprises a breaker  5   c  having a transformer  6   c , a disconnecting switch  8   c , and a grounding switch  9   c  at one end of the breaker  5   c  and a current transformer  7   c , a disconnecting switch  10   c , and a rounding switch  11   c  at the other end of the breaker  5   c . A leader line  12  and a transformer  15  are connected between the unit lines  4   a  and  4   b . A leader line  13  and a transformer  16  are connected between the unit lines  4   b  and  4   c . Further a leader line  14  is connected between the unit lines  4   b  and  4   c  of the busbar connecting line  3   b . Leader lines  13  and  14  connected between the unit lines  4   b  and  4   c  for the busbar connecting line  3   b  constitute main and auxiliary lines. 
     The leader line  12  comprises a breaker  17   a , a grounding switch  18   a , a current transformer  19   a  and a cable head  20   a.    
     The leader line  13  comprises a breaker  17   b , a grounding switch  18   b , a current transformer  19   b  and a cable head  20   b . The leader line  14  comprises a breaker  17   c , a grounding switch  18   c , a current transformer  19   c  and a cable head  20   c.    
     A power receiving line  21   a  and the busbar partitioning line  29   a  are connected to the main busbar  1 . The power receiving line  21   a  comprises a power breaker  22   a , a set of a current transformer  23   a , a disconnecting switch  25   a , and a grounding switch  26   a  which are connected to one end of the power breaker  22   a , a set of a current transformer  24   a , a disconnecting switch  27   a , and a grounding switch  28   a  which are connected to the other end of the power breaker  22   a . The busbar partitioning line  29   a  comprises a power breaker  30   a , a set of a current transformer  31   a , a disconnecting switch  33   a , a grounding switch  34   a , a grounding switch  37   a  and a transformer  38   a  which are connected to one end of the power breaker  30   a , a set of a current transformer  32   a , a disconnecting switch  35   a , and a grounding switch  36   a  which are connected to the other end of the power breaker  30   a.    
     A power receiving line  21   b  and the busbar partitioning line  29   b  are connected to the main busbar  2 . The power receiving line  21   b  comprises a power breaker  22   b , a set of a current transformer  23   b , a disconnecting switch  25   b , and a grounding switch  26   b  which are connected to one end of the power breaker  22   b , a set of a current transformer  24   b , a disconnecting switch  27   b , and a grounding switch  28   b  which are connected to the other end of the power breaker  22   b . The busbar partitioning line  29   b  comprises a power breaker  30   b , a set of a current transformer  31   b , a disconnecting switch  33   b , a grounding switch  34   b , a grounding switch  37   b  and a transformer  38   b  which are connected to one end of the power breaker  30   b , a set of a current transformer  32   b , a disconnecting switch  35   b , and a grounding switch  36   b  which are connected to the other end of the power breaker  30   b.    
     The power receiving lines  21   a  and  21   b  receive power from an upstream power system or an adjoining gas-insulated switching device, send it to the busbar connecting lines  3   a  to  3   c  via the main busbars  1  and  2 , then to a downstream power system via the line leader lines  12  to  14 . 
     Further, power is sent to the busbar partitioning lines  29   a  and  29   b  via the main busbars  1  and  2 , and then to the adjoining gas-insulated switching device. 
     FIG. 1 to FIG. 4 show the layout of components of an actual gas-insulated switching device to which the circuit configuration of FIG. 5 is applied. The gas-insulated switching device of this embodiment is designed to be installed in an indoor substation and supply power to a downstream power system via cables. The indoor substation is made up with a ground section and an underground section. The ground section comprises major components constituting the gas-insulated switching device and the underground section contains a cable section for supplying power to a downstream power system. 
     The main busbars  1  and  2  are oppositely disposed in parallel to each other. The busbar connecting lines  3   a  to  3   c  which connect the busbars  1  and  2  are disposed in parallel to each other and perpendicularly to the busbars  1  and  2  therebetween. The busbar connecting lines  3   a  to  3   c  comprise single-phase lines  50   a  to  50   c  which are disposed in parallel to each other along the main busbars  1  and  2 . The single-phase lines  50   a  to  50   c  are composed of breaker units  51   a  to  51   c.    
     The power breaker units  51   a  and  51   b  are connected to each other with a breaker connecting unit  52   a  and the breaker units  51   b  and  51   c  are connected to each other with a breaker connecting unit  52   b . In other words, the breaker units  51   a ,  51   b , and  51   c  are connected in series by means of the breaker connecting units  52   a  and  52   b . The breaker connecting unit  51   a  is a power breaker  5   a  and comprises a breaker section  53   a  and an operator  54   a . The breaker connecting unit  51   b  is a power breaker  5   b  and comprises a breaker section  53   b  and an operator  54   b . The breaker connecting unit  51   c  is a power breaker  5   c  and comprises a breaker section  53   c  and on operator  54   c.    
     The breaker sections  53   a  to  53   c  houses electric contacts in a cylindrical tank in which sulfur hexafluoride SF 6  (insulating medium) is hermetically sealed. These electric contacts are mechanically connected to the corresponding operators  54   a  to  54   c  by means of link mechanisms to be horizontally opened by the operators  54   a  to  54   c . The operators  54   a  to  54   c  are respectively located on the lower left ends of the corresponding breaker sections  53   a  to  53   c . Each of the cylindrical tanks of the breaker sections  53   a  to  53   c  is a horizontal grounded metallic airtight container whose longitudinal central axis is in parallel to the ground. The cylindrical tanks of the breaker sections  53   a  to  53   c  are placed in a plane so that their longitudinal central axes may be aligned. This embodiment suppresses the height of each breaker unit by using a horizontal cylindrical tank. The tank to be hereinafter explained is what is explained above, that is, the tank is a horizontal grounded metallic airtight container filled with SF 6 . 
     The breaker connecting units  52   a  and  52   b  stand upright from the adjoining breaker units to connect the breaker units. The breaker connecting unit  52   a  comprises upright sections  55   a  and  56   a  and a horizontal section  57   a  which connects these upright sections  55   a  and  56   a  to level. The breaker connecting unit  52   b  comprises upright sections  55   b  and  56   b  and a horizontal section  57   b  which connects these upright sections  55   b  and  56   b  to level. 
     The upright section  55   a  consists of a cross-shaped branch type tank which contains a disconnecting switch  10   a  and a grounding switch  11   a ) and is mounted on the further end (with respect to the main busbar  1   a ) of the tank enclosure of the breaker section  53   a  by means of a current transformer unit  59  which is a cylindrical tank containing a current transformer  7   a.    
     A current transfer unit  64  is connected to the upright section  55   a  at the side closer to the main busbar and has a transformer  15  in a cylindrical tank. The current transfer unit  64  is placed in a space between the upright section  55   a  and the busbar connecting units  66   a  to  66   c . The upright section  56   a  is a T-shaped branch type tank which contains a disconnecting switch  8   b  and a grounding switch  9   b  and is mounted on the tank enclosure of the breaker  53   b  at the end closer to the breaker  53   a  by means of a current transformer unit  60 . The current transformer unit  60  is a cylindrical tank containing a current transformer  6   b . The horizontal section  57   a  comprises a cross-shaped branch tank which contains a disconnecting switch  17   a  and a grounding switch  18   a  and a cylindrical tank which contains a connecting busbar. 
     The upright section  55   b  is a T-shaped branch type tank which contains a disconnecting switch  8   c  and a grounding switch  9   c  and is mounted on the tank enclosure of the breaker  53   c  at the further end (with respect to the main busbar  1   b  by means of a current transformer unit  62 . The current transformer unit  62  is a cylindrical tank containing a current transformer  6   c . The current transformer unit  65  is connected to the upright section  55   b  at the side closer to the main busbar  1   b . The transformer unit  65  comprises a cylindrical tank containing a transformer  16  and is placed in a place between the upright section  55   b  and the busbar connecting units  67   a  to  67   c  to be explained later. The upright section  56   b  is a T-shaped branch type tank which contains a disconnecting switch  10   b  and a grounding switch  11   b  and is mounted on the tank enclosure of the breaker  53   b  at the end closer to the breaker  53   c  by means of a current transformer unit  61 . The current transformer unit  61  is a cylindrical tank containing a current transformer  7   b.    
     As for the busbar connecting lines  3   a  and  3   c , the horizontal section  57   b  comprises a cross-shaped branch tank which contains a disconnecting switch  17   b  and a grounding switch  18   b  and a cylindrical tank which contains a connecting busbar. As for the busbar connecting lines  3   b , the horizontal section  57   b  comprises a cross-shaped branch tank which contains a disconnecting switch  17   b  and a grounding switch  18   b  and a cross-shaped branch tank which contains a disconnecting switch  17   c  and a grounding switch  18   c . The horizontal sections  57   a  and  57   b  are disposed on a plane. 
     A busbar connecting unit  66   a  is mounted on the tank enclosure of the breaker section  53   a  which constitutes the breaker unit  51   a  of the single-phase line  50   a  at the end closer to the main busbar  1   a  by means of the current transformer  58 . A busbar connecting unit  66   b  is mounted on the tank enclosure of the breaker section  53   a  which constitutes the breaker unit  51   a  of the single-phase line  50   b  at the end closer to the main busbar  1   a  by means of the current transformer  58 . A busbar connecting unit  66   c  is mounted on the tank enclosure of the breaker section  53   a  which constitutes the breaker unit  51   a  of the single-phase line  50   c  at the end closer to the main busbar  1   a  by means of the current transformer  58 . Each of the busbar connecting units  66   a  to  66   c  accommodates a disconnecting switch  8   a , a grounding switch  9   a , and a connecting busbar in a cylindrical tank standing upright from the end of the tank enclosure. 
     A busbar connecting unit  67   a  is mounted by means of the current transformer unit  63  on the tank enclosure of the breaker section  53   c  (which constitutes the breaker unit  51   c  of the single-phase line  50   a ) at the end closer to the main busbar  1   b . The current transformer unit  63  has a current transformer  7   c  in a cylindrical tank. A busbar connecting unit  67   b  is mounted by means of the current transformer unit  63  on the tank enclosure of the breaker section  53   c  (which constitutes the breaker unit  51   c  of the single-phase line  50   b ) at the end closer to the main busbar  1   b . A busbar connecting unit  67   c  is mounted by means of the current transformer unit  63  on the tank enclosure of the breaker section  53   c  (which constitutes the breaker unit  51   c  of the single-phase line  50   c ) at the end closer to the main busbar  1   b . Each of the busbar connecting units  67   a  to  67   c  accommodates a disconnecting switch  10   c , a grounding switch  11   c , and a connecting busbar in a cylindrical tank standing upright from the end of the tank enclosure. 
     The main busbar  1  comprises basbar units  68   a  to  68   c  each of which has a busbar conductor in a cylindrical tank and is placed in the outside of the main busbar  1  and  2  (opposite to the busbar connecting units  66   a  to  66   c ). The busbar units  68   a  to  68   c  are vertically disposed along the busbar connecting units  66   a  to  66   c . The busbar unit  68   a  is connected to the busbar connecting unit  66   a . The busbar unit  68   b  is connected to the busbar connecting unit  66   b . The busbar unit  68   c  is connected to the busbar connecting unit  66   c.    
     The main busbar  2  comprises basbar units  698   a  to  69   c  each of which has a busbar conductor in a cylindrical tank and is placed in the outside of the main busbar  1  and  2  (opposite to the busbar connecting units  67   a  to  67   c ). The busbar units  69   a  to  69   c  are vertically disposed along the busbar connecting units  67   a  to  67   c . The busbar unit  69   a  is connected to the busbar connecting unit  67   a . The busbar unit  69   b  is connected to the busbar connecting unit  67   b . The busbar unit  69   c  is connected to the busbar connecting unit  67   c.    
     This embodiment disposes the busbar connecting units  66   a  to  66   c  ( 67   a  to  67   c ) and the busbar units  68   a  to  68   c  ( 69   a  to  69   c ) across the main busbar  1  and  2 , but they can be in the same side with respect to the main busbar  1  and  2 . 
     The leader line  12  consists of a connecting busbar unit  70   a , a current transformer unit  71   a , and a cable head unit  72   a . The connecting busbar unit  70   a  has a connecting busbar in a cylindrical tank, is connected to the cross-shaped branch tank which constitutes the horizontal section  57   a  of the breaker connection unit  52   a , and goes down vertically. 
     The current transformer unit  71   a  has a current transformer  19   a  in a cylindrical tank. The cable head unit  72   a  has a cable head  20   a  which is connected to the cable  73   a  in a cylindrical tank. 
     The leader line  13  consists of a connecting busbar unit  70   b , a current transformer unit  71   b , and a cable head unit  72   b . The connecting busbar unit  70   b  has a connecting busbar in a cylindrical tank, is connected to the cross-shaped branch tank which constitutes the horizontal section  57   b  of the breaker connection unit  52   b , and goes down vertically. The current transformer unit  71   b  has a current transformer  19   b  in a cylindrical tank. The cable head unit  72   b  has a cable head  20   a  which is connected to the cable  73   b  in a cylindrical tank. 
     The leader line  14  consists of a connecting busbar unit  70   c , a current transformer unit  71   c , and a cable head unit  72   c . The connecting busbar unit  70   c  has a current transformer  19   c  in a cylindrical tank and is connected to the cross-shaped branch tank (different from the cross-shaped branch tank to which the connecting busbar unit  70   b  is connected) which constitutes the horizontal section  57   b  of the breaker connection unit  52   b  of the busbar connecting line  3   b . The current transformer unit  71   c  has a current transformer  19   c  in a cylindrical tank. The cable head unit  72   c  has a cable head  20   c  which is connected to the cable  73   c  in a cylindrical tank. 
     The connecting busbar unit  70   c  cannot go down vertically because the operator  54   b  of the breaker unit  51   b  which constitutes the busbar connecting line  3   b  is in its way. Even if the connecting busbar unit  70   c  is vertically drawn down, the cable  73   c  cannot be drawn out because the leader line  13  is in its way. 
     To solve this problem, this embodiment horizontally to the side of the connecting busbar unit  70   c  slantwise along the main busbar  2 , and then vertically draws the connecting busbar unit  70   c  along the connecting bus unit  70   b.    
     If the cable head unit  72   c  of the leader line  14  is disposed next to the cable head unit  72   b  of the leader line  13  in an identical position, the phase-to-phase distance of respective single-phase lines  50   a  to  50   c  which constitutes the busbar connecting line  3   b  must be made greater to secure an insulating distance between the cable head units  72   b  and  72   c . However, this increases the physical installation space of the gas-insulated switching device. 
     To secure an insulating distance between the cable head units  72   b  and  72   c  without increasing the phase-to-phase distance of respective single-phase lines  50   a  to  50   c , this embodiment horizontally draws the vertical connecting busbar unit  70   c  apart from the leader line  12  and places the cable head unit  72   c  above the cable head unit  72   b  and away from the leader line  12  before the cable head unit  72   b.    
     The power receiving line  21   a  comprises breaker units  74   a  to  74   c  which are disposed between the main busbars  1  and  2  to be perpendicular to the main busbar  1  and horizontally along the main busbar  1 . The breaker units  74   a  to  74   c  are provided along with a breaker unit  51   a  of the busbar connecting line  3   a  and horizontally as the breaker unit  51   a  is provided. The breaker units  74   a  to  74   c  comprise a breaker section  76   a  and an operator  77   a . The breaker section  76   a  and the operator  77   a  are built up in the same manner as those of the breaker units  51   a  to  51   c.    
     The enclosure of a cylindrical tank constituting the breaker section  76   a  of the breaker unit  74   a  has a busbar connecting unit  78   a  on one end of the enclosure by means of a current transformer unit  80  and a busbar connecting unit  79   a  on the other end of the enclosure by means of a current transformer unit  81 . The current transformer unit  80  accommodates a current transformer  23   a  in the cylindrical tank and the current transformer unit  81  accommodates a current transformer  24   a  in the cylindrical tank. 
     The enclosure of a cylindrical tank constituting the breaker section  76   a  of the breaker unit  74   b  has a busbar connecting unit  78   b  on one end of the enclosure by means of a current transformer unit  80  and a busbar connecting unit  79   b  on the other end of the enclosure by means of a current transformer unit  81 . The enclosure of a cylindrical tank constituting the breaker section  76   a  of the breaker unit  74   c  has a busbar connecting unit  78   c  on one end of the enclosure by means of a current transformer unit  80  and a busbar connecting unit  79   c  on the other end of the enclosure by means of a current transformer unit  81 . 
     Each of the busbar connecting units  78   a  to  78   c  has a disconnecting switch  25   a , a grounding switch  26   a , and a connecting busbar in a cylindrical tank and stands upright on one end of the enclosure of the tank. The busbar units  68   a  to  68   c  constituting the main bus bar  1  and the busbar connecting units  78   a  to  78   c  are across the busbar connecting units  78   a  to  78   c . The busbar units  68   a  to  68   c  are disposed vertically along the busbar connecting units  78   a  to  78   c . The busbar connecting units  78   a  is connected to the busbar unit  68   a . The busbar connecting units  78   b  is connected to the busbar unit  68   b . Similarly, the busbar connecting units  78   c  is connected to the busbar unit  68   c.    
     Each of the busbar connecting units  79   a  to  79   c  has a disconnecting switch  27   a , a grounding switch  28   a , and a connecting busbar in a cylindrical tank and stands upright on the other end of the enclosure of the tank. 
     The busbar units  68   a  to  68   c  constituting the main bus bar  1  and the busbar connecting units  79   a  to  79   c  are across the busbar connecting units  78   a  to  78   c . The busbar units  68   a  to  68   c  are disposed vertically along the busbar connecting units  79   a  to  79   c . The busbar connecting units  79   a  is connected to the busbar unit  68   a . The busbar connecting units  79   b  is connected to the busbar unit  68   b . Similarly, the busbar connecting units  79   c  is connected to the busbar unit  68   c.    
     The power receiving line  21   b  comprises the breaker units  75   a  to  75   c  which are disposed between the main busbars  1  and  2  so as to be perpendicular to the main busbar  2  and horizontally along the main busbar  2 . The breaker units  75   a  to  75   c  are provided along with the breaker unit  51   c  of the busbar connecting line  3   a  and horizontally as the breaker unit  51   c  does. The breaker units  75   a  to  75   c  are respectively composed of a breaker section  76   b  and the operator  77   b  which are the same as those of the breaker units  51   a  to  51   c.    
     The enclosure of the cylindrical tank constituting the breaker section  76   b  of the breaker unit  75   a  has a busbar connecting unit  82   a  on one end of the tank enclosure by means of the current transformer  84  and a busbar connecting unit  83   a  on the other end of the tank enclosure by means of the current transformer  85 . The current transformer  84  has a current transformer  23   b  in the cylindrical tank and the current transformer  85  has a current transformer  24   b  in the cylindrical tank. The enclosure of the cylindrical tank constituting the breaker section  76   b  of the breaker unit  75   b  has a busbar connecting unit  82   b  on one end of the tank enclosure by means of the current transformer  84  and a busbar connecting unit  83   b  on the other end of the tank enclosure by means of the current transformer  85 . 
     The enclosure of the cylindrical tank constituting the breaker section  76   b  of the breaker unit  75   c  has a busbar connecting unit  82   c  on one end of the tank enclosure by means of the current transformer  84  and a busbar connecting unit  83   c  on the other end of the tank enclosure by means of the current transformer  85 . 
     Each of the busbar connecting units  82   a  to  82   c  has a disconnecting switch  25   b , a grounding switch  26   b , and a connecting busbar in a cylindrical tank and stands upright on one end of the enclosure of the tank. The busbar units  69   a  to  69   c  constituting the main bus bar  2  and the busbar connecting units  82   a  to  82   c  are across the busbar connecting units  83   a  to  83   c . The busbar units  69   a  to  69   c  are disposed vertically along the busbar connecting units  82   a  to  82   c . The busbar connecting units  82   a  is connected to the busbar unit  69   a . The busbar connecting units  82   b  is connected to the busbar unit  69   b . Similarly, the busbar connecting units  82   c  is connected to the busbar unit  69   c.    
     Each of the busbar connecting units  83   a  to  83   c  has a disconnecting switch  27   b , a grounding switch  28   b , and a connecting busbar in a cylindrical tank and stands upright on the other end of the enclosure of the tank. The busbar units  69   a  to  69   c  constituting the main bus bar  2  and the busbar connecting units  82   a  to  82   c  are across the busbar connecting units  83   a  to  83   c . The busbar units  69   a  to  69   c  are disposed vertically along the busbar connecting units  83   a  to  83   c . The busbar connecting units  83   a  is connected to the busbar unit  69   a . The busbar connecting units  83   b  is connected to the busbar unit  69   b . Similarly, the busbar connecting units  83   c  is connected to the busbar unit  69   c.    
     The busbar partitioning lines  29   a  and  29   b  are connected to the main busbars of an adjoining gas-insulated switching device and built up almost in the same manner as the power receiving lines  21   a  and  21   b . Therefore, identical reference numerals are assigned to units constituting the busbar partitioning lines  29   a  and  29   b  and to units constituting the power receiving lines  21   a  and  21   b  in the drawings and part of the description is omitted. 
     A cylindrical tank constituting each of the connecting busbar units  78   a  to  78   c  of the busbar partitioning line  29   a  contains a disconnecting switch  35   a , a grounding switch  36   a , and a connecting busbar in it. The cylindrical tank constituting the current transformer unit  80  of the busbar partitioning line  29   a  contains a current transformer  32   a . A cross-shaped branch type tank constituting each of the connecting busbar unit  79   a  to  79   c  of the busbar partitioning line  29   a  contains a disconnecting switch  33   a , grounding switches  34   a  and  37   a , and a connecting busbar in it. A transformer unit  86  containing a transformer  38   a  in a cylindrical tank is connected to the cross-shaped branch type tank constituting the connecting busbar units  79   a  to  79   c  of the busbar partitioning line  29   a  at the side opposite to the side on which the connecting busbar units  78   a  to  78   c  exist. The current transformer unit  81  of the busbar partitioning line  29   a  contains a current transformer  32   a  in a cylindrical tank. 
     A cylindrical tank constituting each of the connecting busbar units  82   a  to  82   c  of the busbar partitioning line  29   b  contains a disconnecting switch  35   b , a grounding switch  36   b , and a connecting busbar in it. The cylindrical tank constituting the current transformer unit  84  of the busbar partitioning line  29   b  contains a current transformer  32   b . A cross-shaped branch type tank constituting each of the connecting busbar unit  83   a  to  83   c  of the busbar partitioning line  29   b  contains a disconnecting switch  33   b , grounding switches  34   b  and  37   b , and a connecting busbar in it. A transformer unit  87  containing a transformer  38   b  in a cylindrical tank is connected to the cross-shaped branch type tank constituting the connecting busbar units  82   a  to  82   c  of the busbar partitioning line  29   b  at the side opposite to the side on which the connecting busbar units  82   a  to  82   c  exist. The current transformer unit  85  of the busbar partitioning line  29   b  contains a current transformer  31   b  in a cylindrical tank. 
     Judging from the above description, this embodiment builds up the busbar connecting lines  3   a  to  3   c  with horizontal breaker units  51   a  to  51   c  and consequently can reduce the physical installation height of the gas-insulated switching device. 
     Further, this embodiment can reduce the distance between the main busbars  1  and  2  of the gas-insulated switching device as the busbar units  68   a  to  68   c  constituting the main busbar  1  are vertically disposed along the busbar connecting units  66   a  to  66   c  and the busbar units  69   a  to  69   c  constituting the main busbar  2  are vertically disposed along the busbar connecting units  67   a  to  67   c . Therefore, this embodiment reduces the installation space while suppressing the installation height of the gas-insulated switching device. 
     Further, this embodiment connects the breaker units  51   a  and  51   b  with the breaker connecting units  52   a  having the upright sections  55   a  and  56   a  and the breaker units  51   b  and  51   c  with the breaker connecting units  52   b  having the upright sections  55   b  and  56   b  and consequently can reduce the lengths of the horizontal sections  57   a  and  57   b  which constitute the breaker connecting units  52   a  and  42   b  and the lengths between the main busbars  1  and  2  of the gas-insulated switching device. Therefore, this embodiment can reduce the dimensions between the main busbars of the gas-insulated switching device and consequently reduce the physical installation area of the gas-insulated switching device. 
     Furthermore, this embodiment draws out leader lines  13  and  14  from a single point on the horizontal section  57   b  of the breaker connecting unit  52   b  and draws out the connecting busbar unit  70   c  of the leader line  14  slantwise along the main busbar  2  and horizontally apart from the connecting busbar unit  70   b  of the leader line  13 . As the result, this embodiment can draws out the leader lines  13  and  14  from a single point on the horizontal section  57   b  of the horizontal section  52   b  without increasing the dimensions of the horizontal section  57   b  which constitutes the breaker connecting unit  52   b . Therefore, even when two leader lines are drawn from a single point on the horizontal section of the breaker connecting unit, it never happens that the distance between the main busbars  1  and  2  of the gas-insulated switching device increases and that the physical installation space of the gas-insulated switching device increases. 
     Although, in the above description, this embodiment draws out the connecting busbar unit  70   c  of the leader line  14  slantwise along the main busbar  2  and apart from the connecting busbar unit  70   b  of the leader line  13 , it is possible that the connecting busbar unit  70   c  is first drawn out in parallel to the main busbar  2 , and then at right angles to the main bus bars  1  and  2 . In this case, the connecting busbars can be made shorter when drawn out slantwise. Further, it is possible to draw out the connecting busbar unit  70   c  of the leader line  14  (which is connected to the single phase lines  50   a  to  50   c ) between phases of the busbar connecting lines  3   a  to  3   c  (or between the single-phase lines  50   a  and  50   b  and between the single-phase lines  50   b  and  50   c ). For example, the connecting busbar unit  70   c  of the leader line  14  which is connected to the single phase line  50   a  can be drawn between the single-phase lines  50   a  and  50   b  and the connecting busbar unit  70   c  of the leader line  14  which is connected to the single phase lines  50   b  and  50   c  can be drawn between the single-phase lines  50   b  and  50   c.    
     Further, this embodiment disposes the transformer unit  64  connected to the upright section  55   a  of the breaker connecting unit  52   a  in a space between the upright section  55   a  and the busbar connecting units  66   a  to  66   c  and the transformer unit  65  connected to the upright section  55   b  of the breaker connecting unit  52   b  in a space between the upright section  55   b  and the busbar connecting units  67   a  to  67   c . Consequently, this embodiment can suppress the transformer units  64  and  65  from increasing the installation height of the gas-insulated switching device. 
     (Embodiment 2) 
     Referring to FIG. 6 to FIG. 8, a second embodiment of the present invention will be explained below. FIG. 6 to FIG. 8 show the component layouts of a gas-insulated switching device which is a second embodiment of the present invention. This embodiment is an improvement of the first embodiment. 
     The main busbars  1  and  2 , the busbar connecting lines  3   a  to  3   c , the power receiving lines  21   a  and  21   b  and the busbar partitioning lines  29   a  and  29   b  of this embodiment are built up in the same manner as those of the first embodiment. Therefore, identical reference numerals are assigned to them in the drawings and part of the description is omitted. The gas-insulated switching device of the second embodiment is installed in an outdoor substation and sends power to a downstream power system through bushings. Therefore, the configuration of the leader lines  12  to  14  of this embodiment is different from that of the first embodiment. 
     The leader line  12  comprises a connecting busbar unit  70   a , a current transformer unit  71   a , and a bushing  88   a . The connecting busbar unit  70   a  is connected to a cross-shaped branch type tank which constitutes the horizontal section  57   a  of the breaker connecting unit  52   a  via the current transformer unit  71   a , stands upright, bends at right angle towards the busbar  1 , extends horizontally, and reaches to the bushing  88   a  on a steel tower at the main busbar  1  side. 
     The leader line  13  comprises a connecting busbar unit  70   b , a current transformer unit  71   b , and a bushing  88   b . The connecting busbar unit  70   b  is connected to a cross-shaped branch type tank which constitutes the horizontal section  57   b  of the breaker connecting unit  52   b  via the current transformer unit  71   b , stands upright, bends at right angle towards the busbar  2 , extends horizontally, and reaches to the bushing  88   a  on a steel tower at the main busbar  2  side. 
     The leader line  14  comprises a connecting busbar unit  70   c , a current transformer unit  71   c , and a bushing  88   c . The connecting busbar unit  70   c  is connected to the cross-shaped branch tank (different from the cross-shaped branch tank to which the connecting busbar unit  70   b  is connected via a current transformer unit  71   b ) which constitutes the horizontal section  57   b  of the breaker connection unit  52   b  of the busbar connecting line  3   b . The connecting busbar unit  70   c  is drawn slantwise along the main busbar  2  and horizontally to the side of the connecting busbar unit  70   b  and rises upright along the connecting busbar unit  70   b.    
     In this case, the connecting busbar unit  70   c  is above the connecting busbar unit  70   b . Then the connecting busbar unit  70   c  bends at right angle towards the busbar  2 , extends horizontally, and reaches the bushing  88   c  on a steel tower at the main busbar  2  side. 
     As explained above, the second embodiment draws out the connecting busbar unit  70   c  slantwise along the main busbar  2  and horizontally to the side of the connecting busbar unit  70   b  and rises it upright along the connecting busbar unit  70   b . Consequently, even when both the leader lines  13  and  14  are drawn out from a single point on the horizontal section  57   b  of the breaker connecting unit  52   b , the leader lines  13  and  14  can be drawn in the same direction. It is also possible to horizontally draw the connecting busbar unit  70   c  in parallel to the main busbar  2  and to horizontally draw it perpendicularly to the line connecting the ain busbars  1  and  2 . 
     Further, this embodiment places the connecting busbar unit  70   c  above the connecting busbar unit  70   b , bends it at a right angle towards the main busbar  2 , and extends it horizontally. When the connecting busbar units  70   b  and  70   c  are placed side by side horizontally, it is necessary to widen the phase-to-phase distances of the single-phase lines  50   a  to  50   c  which constitutes the busbar connecting line  3   b  to secure the insulating distance between the connecting busbar units  70   b  and  70   c . This unwontedly increases the installation space of the gas-insulated switching device. However, as the connecting busbar unit  70   c  is placed above the connecting busbar unit  70   b , this embodiment can secure the insulating distance between the connecting busbar units  70   b  and  70   c  without increasing the phase-to-phase distances of the single-phase lines  50   a  to  50   c  constituting the busbar connecting line  3   b . The other parts of this embodiment equivalent to those of the first embodiment have the same effects as those of the first embodiment. 
     FIELD OF THE INVENTION 
     The present invention is applicable to a gas-insulated switching device whose installation height and space are limited, particularly to a gas-insulated switching device to be installed in an electric station such as an indoor substation or an underground substation where the physical spaces for installation are limited.