Patent Publication Number: US-6337452-B1

Title: Gas insulated switchgear with flange-spacer assembly

Description:
This is a continuation application of U.S. Ser. No. 09/366,323, filed Aug. 2, 1999, now U.S. Pat. No. 6,188,034. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a gas insulated switchgear suited to a dismantling operation of a unit. A gas insulated switchgear is superior in size reduction, insulation performance, and safety and widely used in electric plants such as substations. A gas insulated switchgear includes a combination of a plurality of components such as a breaker, disconnecting switches, grounding switches, a potential transformer, and others and a power supply conductor for electrically connecting these devices to each other in a closed enclosure charged with insulating gas. For example, the gas insulating switchgear described in Japanese Patent Application Laid-Open 10-75513 includes a combination of line side units having a bus unit having a bus conductor, breaker unit having a breaker, arrester, potential transformer, and others. 
     The aforementioned units are connected via insulating spacers so as to keep air-tightness between the units. For that purpose, a flange is formed in each unit so as to connect each insulating spacer. For example, in the gas insulating switchgear described in Japanese Patent Application Laid-Open 10-75513, the flange in each unit is formed as an outer flange and when dismantling the units, in the state that the insulating spacer is attached to the flange of one unit, the other unit is separated. In addition to this gas insulating switchgear in which the flange of each unit is formed as an outer flange, there are ones described in Japanese Utility Model Application Laid-Open 62-98420 and Japanese Utility Model Application Laid-Open 63-74011. Particularly in the gas insulating switchgears described in Japanese Patent Application Laid-Open 64-77411 and Japanese Utility Model Application Laid-Open 59-183129, the flange of one unit is formed as an outer flange and the flange of the other unit is formed as an inner flange. 
     SUMMARY OF THE INVENTION 
     In a conventional gas insulating switchgear in which the flange of each unit is formed as an outer flange, the mechanical strength is relatively weak and there are many parts to be used. In a conventional gas insulating switchgear in which the flange of one unit is formed as an outer flange and the flange of the other unit is formed as an inner flange, when dismantling the units, the insulating spacer can be attached only to either one of the outer or inner flanges. 
     The present invention is planned in view of the above situations and an object thereof is to provide a gas insulated switchgear for dismantling units in the state that an insulating spacer can be attached to the both flanges of the units even if an inner flange is used. Another object of the present invention is to improve the dismantling operability of a gas insulated switchgear in which the flange of one unit is formed as an outer flange and the flange of the other unit is formed as an inner flange. 
     The gas insulated switchgear of the first present invention includes a unit having an inner flange, a unit having an outer flange, and insulating spacers existing between the flanges of the units, wherein a closed-end tapped hole is formed in the inner flange, and an idle hole is formed in the outer flange, and a tapped hole with a larger diameter than that of the hole in the inner flange is formed in each insulating spacer. 
     The gas insulated switchgear of the second present invention includes a unit having an inner flange, a unit having an outer flange, and insulating spacers existing between the flanges of the units, wherein when separating the inner flange side in the state that the insulating spacer is attached to the outer flange side, a bolt is screwed into a tapped hole made in the insulating spacer so as to connect the outer flange to the insulating spacer and when separating the outer flange side in the state that the insulating spacer is attached to the inner flange side, a bolt is screwed into a tapped hole made in the inner flange so as to connect the inner flange to the insulating spacer. 
     The gas insulated switchgear of the third present invention includes a unit having an inner flange, a unit having an outer flange, and insulating spacers existing between the flanges of the units, wherein a plurality of first holes with a diameter of D1 are formed in the periphery of the outer flange, and a plurality of second holes with a diameter of D2 are formed in the periphery of each insulating spacer, and a plurality of third holes with a diameter of D3 are formed in the periphery of the inner flange, and the relationship between the diameters of the holes is set to D1≧D2≧D3. 
     In the gas insulated switchgear of the present invention, in the state that the insulating spacer is attached to the flange of one unit, the other unit can be separated or in the state that the insulating spacer is attached to the flange of the other unit, one unit can be separated, so that the maintenance and inspection operation or the trouble recovery operation can be performed for a unit not to be maintained and inspected or a unit free from a trouble unless it is exposed to the air. As a result, the space for gas collection, evacuation, and gas charging can be made smaller, so that the unit dismantling time can be shortened. Furthermore, the space that there is a possibility of mixing of foreign substances causing dielectric breakdown can be made smaller, so that the reliability of the gas insulated switchgear can be improved. 
     In the connection structure that insulating spacers exist between outer flanges of two units, a large space is required, and moreover the mechanical strength is relatively weak, and it takes a lot of time to attach and remove stud bolts, and there are many parts used. However, in the gas insulated switchgear of the present invention, the outer diameter can be made smaller and the mechanical strength can be ensured. Furthermore, there is no need to use stud bolts, and as a result, the operability can be improved and the number of parts can be reduced. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross sectional view showing the structure of a gas insulated switchgear of an embodiment of the present invention. 
     FIG. 2 is a cross sectional view taken along line  11 — 11  shown in FIG.  1 . 
     FIG. 3 is an enlarged cross sectional view showing an enlarged structure of the circular portion  111  shown in FIG.  1 . 
     FIG. 4 is a cross sectional view for explaining separation of the inner flange side of an embodiment of the present invention. 
     FIG. 5 is a cross sectional view for explaining separation of the outer flange side of an embodiment of the present invention. 
     FIG. 6 is a plan view showing the arrangement structure of holes of an outer flange of an embodiment of the present invention. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     The structure of a gas insulated switchgear of an embodiment of the present invention is shown in FIGS. 1 and 2. The gas insulated switchgear of this embodiment has a bus unit  1 , a breaker unit  2 , and a line side unit  3 , and assuming the breaker unit  2  as a vertical axis, two bus units  1  are connected up and down in line with each other on one side of the axis, and the line side unit  3  is attached on the other side. An operating device  4  is arranged below the breaker unit  2 . A control box  5  is arranged on the side of the operating device  4  on the bus unit  1  side. 
     The bus unit  1  houses bus conductors  6  for three phases in a batch in a bus enclosure  7  charged with insulating gas. The bus enclosure  7  is a grounded metal enclosure, which is formed by combining a cylindrical enclosure  7   a  extended in the extending direction to the bus conductors  6  and a cylindrical enclosure  7   b  extended in the orthogonal direction to the cylindrical enclosure  7   a . The bus conductors  6  are arranged so that the three conductors are located at the vertexes of an isosceles triangle respectively and it comprises bus conductors  6   a  and  6   b  arranged in a column on the center line of the cylindrical enclosure  7   a  and a bus conductor  6   c  arranged on the breaker unit  2  side of the bus conductors  6   a  and  6   b  of the cylindrical enclosure  7   a . A flange is provided at both ends of the cylindrical enclosure  7   a  respectively and an expansion joint  8  comprising an expansion bellows is attached to the flange at one end. 
     A branch conductor  9   a  branches from the bus conductor  6   a , a branch conductor  9   b  from the bus conductor  6   b , and a branch conductor  9   c  from the bus conductor  6   c  on the breaker unit  2  side. The branch conductors  9   a ,  9   b , and  9   c  are arranged in a column on the center line of the cylindrical enclosure  7   b  and a movable electrode  10  is provided at each center part of the branch conductors. The movable electrodes  10  are driven by operating devices  11  provided in the space between the upper bus enclosure  7  and the lower bus enclosure  7  and make a reciprocating motion in each conductor. 
     Each of the bus units is attached to the breaker unit  2  via an insulating spacer  12 . The insulating spacers  12  are used to keep air-tightness between each of the bus units  1  and the breaker unit  2 . On the center line of the insulating spacers  12 , conductor connections  13  to one end of which a reciprocating conductor  18  in the breaker unit  2  is attached are horizontally arranged in a line. On the other end of each of the conductor connections  13 , a fixed electrode  15  is provided via a conductor  14 . Each of the fixed electrodes  15  forms a counterpart to each of the movable electrodes  10  so as to form a disconnecting switch and it is arranged opposite to each of the movable electrodes  10  so as to freely connect and disconnect to them. 
     The breaker unit  2  houses breakers  17  for three phases in a batch in a breaker enclosure  16 . The breaker enclosure  16  is formed by combining a cylindrical enclosure  16   a  extended in the perpendicular direction, a cylindrical enclosure  16   b  extended on the side of the bus unit  1  and the line side unit  3  above the cylindrical enclosure  16   a , and a cylindrical enclosure  16   b  extended on the side of the bus unit under the cylindrical enclosure  16   a . On the center line of the cylindrical enclosure  16   a , the breakers  17  are arranged in a line in the same direction as the extending direction to the bus conductors  6 . 
     The conductor connection  13  provided in the upper insulating spacer  12  and the conductor connection  13  provided in the lower insulating spacer  12  are connected by the reciprocating conductor  18 . To the lower part of the reciprocating conductor  18 , a conductor  19  connected to the lower part of the breaking section of the breaker  17  is attached. At the bottom of the reciprocating conductor  18 , a fixed electrode  20  is provided. The fixed electrode  20  forms a grounding device by forming a counterpart to a movable electrode  21  driven by an operation unit (not shown in the drawing) provided outside the enclosure of the breaker unit  2  and it is arranged opposite to the movable electrode  21  so as to freely connect and disconnect to them. 
     The breaker unit  2  and the line side unit  3  are connected to each other via an insulating spacer  22 . The insulating spacer  22  is used to keep air-tightness between the breaker unit  2  and the line side unit  3 . On the center line of the insulating spacer  22 , a conductor connection  23  to one end of which a conductor  30  in the line side unit  3  is attached is horizontally arranged in a line. At the other end of the conductor connection  23 , a connection conductor  24  connected to the upper part of the breaker  17  is attached. The connection conductor  24  has a branch section branching on the breaking section side and at its end, a fixed electrode  25  is provided. The fixed electrode  25  forms a grounding device by forming a counterpart to a movable electrode  26  driven by an operation unit (not shown in the drawing) provided outside the enclosure of the breaker unit  2  and it is arranged opposite to the movable electrode  26  so as to freely connect and disconnect to them. 
     The breaker positioned at the center of the breakers  17  is arranged on a straight line connecting the one positioned at the center of the conductor connections  13  provided in the insulating spacers  12  and the one positioned at the center of the conductor connections  23  provided in the insulating spacers  22 . The breakers positioned on both sides of the breaker positioned at the center of the breakers  17  are arranged outside the straight line connecting the respective corresponding conductor connections  13  and  23  so as to ensure the insulation distance. Therefore, the conductors positioned on both sides of the conductor positioned at the center of the conductors  19  extend outside the reciprocating conductor  18  and they are connected to the breakers  17 . The breakers  17  are formed cylindrically. However, in this case, each surface in the arrangement direction is made flat so as to reduce the size in the arrangement direction. 
     The line side unit  3  houses line side devices such as an arrester  28  and a potential transformer  29  in a line side enclosure  27 . The line side enclosure  27  is formed by combining a cylindrical enclosure  27   a  extended in the perpendicular direction, a cylindrical enclosure  27   b  extended on the side of the breaker unit  2  above the cylindrical enclosure  27   a , and a cylindrical enclosure  27   b  extended on the opposite side of the breaker unit  2  almost at the center of the cylindrical enclosure  27   a.    
     At the center of a conductor  30  connected to the conductor connection  23 , a movable electrode  31  is provided. The movable electrode  31  is driven by an operating device  32  provided outside the enclosure of the line side unit  3  and makes the reciprocating motion vertically in the conductor  30 . In the area opposite to the movable electrode  31 , a fixed electrode  33  is provided. The movable electrode  31  and the fixed electrode  33  form a disconnecting switch by making a pair. 
     On the lower part in the cylindrical enclosure  27   a , cable heads  34  for three phases are arranged so as to locate at the vertexes of an isosceles triangle respectively. To the cable heads  34 , one end of a conductor  35  is attached. To the other end of the conductor  35 , the fixed electrode  31  is attached. On the side of the cable heads  34  on the side of the breaker unit  2 , the arresters  28  for three phases are arranged so as to locate at the vertexes of an isosceles triangle respectively. The arresters  28  are also connected to the conductor  35 . 
     The arresters  28  and the cable heads  34  are arranged so that the bases of the isosceles triangles formed by them respectively are opposite to each other. Furthermore, they are arranged so that the vertexes of the isosceles triangles are located almost on a concentric circle of the cylindrical enclosure  27   a . By realizing this arrangement, the efficiency of the mounting operation of a current transformer  36  at the time of installation at site can be improved. By realizing this arrangement, the outer diameter of the cylindrical enclosure  27   a  of the line side unit  3  can be made smaller. Furthermore, by realizing this arrangement, the cable heads  34  and the arresters  28  at least for two phases, moreover for the same phase can be arranged close to each other, so that the charging rate of the arresters  28  can be reduced and the life of the arresters  28  can be lengthened. 
     The disconnecting switches comprising a pair of the movable electrode  31  and the fixed electrode  33  are arranged in a line in the same direction as the arrangement direction to the breakers  17  at almost the same position as that of the ones for two phases at a long distance from the breaking unit  2  among the arresters  28 . The potential transformer  29  is arranged above the cable heads  34 . The potential transformer  29  can be attached to or disconnected from the conductor  35  via a separation device  37 . In the conductor  35 , a fixed electrode  38  different from the fixed electrode  33  is provided. The fixed electrode  38  forms a grounding device by forming a counterpart to a movable electrode  40  driven by an operation unit  39  provided outside the enclosure of the line side unit  3  and it is arranged opposite to the movable electrode  40  so as to freely connect and disconnect to them. 
     Under the line side unit  3 , a frame  41  for mounting the line side unit  3  is provided. At the bottom of the enclosure of the line side unit  3 , a base plate  42  is provided and connections  43  of the cable heads  34  are pulled out outside the enclosure of the line side unit  3  via the seal portion of this base plate  42 . Cables  44  are connected to the connections  43 . The current transformers  36  are attached to the cables  44 . 
     On the side of the box for housing the breaker operating device  4  under the line side unit  3 , a monitoring device  45  is attached. To the monitoring device  45 , grounding cables  46  pulled out outside the enclosure of the line side unit  3  from the bottom of each arrester  28  are connected. When the grounding cables  46  are pulled out from the bottoms of the arresters  28  like this, the grounding cables can be shortened, so that the potential superimposed on the operating potential of the arresters  28  is made smaller and the arresters  28  can be precisely operated at the operating potential. 
     The connection structure between the units is shown in FIG.  3 . In this embodiment, an example of the connection structure of the bus unit  1  and the breaker unit  2  will be explained. The arrangement structure of holes of an outer flange is shown in FIG.  6 . At the connection of the bus enclosure  7  of the bus unit  1 , an outer flange  47  is formed. In the outer flange  47 , a plurality of idle holes  48  and  49  are made in the peripheral direction and an O-ring groove  50  is provided outside the idle holes  48  and  49 . An outer flange means a flange in which the idle holes  48  and  49  are located, is outside the outer diameter of the enclosure. 
     At the connection of the breaker enclosure  16  of the breaker unit  2 , an inner flange  51  is formed. In the inner flange  51 , a plurality of tapped holes  52  are made in the peripheral direction and an O-ring groove  50  is provided outside the tapped holes  52 . An inner flange means a flange in which the tapped holes  52  are located is inside the outer diameter of the enclosure. 
     In the O-ring grooves  50  made in the outer flange  47  and the inner flange  51 , O-rings for keeping an airtight seal between the units are mounted. On both sides of the insulating spacer  12  existing between the outer flange  47  and the inner flange  51 , an O-ring groove  53  is made inside the idle holes  48  and  49  made in the outer flange  47  or the tapped holes  52  made in the inner flange  51 . 
     Explaining more concretely, M20 idle holes  48  are provided in 45° -equal arrangement positions, 8 positions in total, on the periphery of the outer flange  47  including the horizontal and vertical directions and M16 idle holes  49  are provided in the other 8 positions. In the  4  horizontal and vertical positions of the insulating spacer  12 , M20 tapped holes  54  are provided and M16 idle holes  55  are provided in the other  12  positions. M16 closed-end tapped holes  52  are provided in the 22.5° -equal arrangement positions, 16 positions in total, on the periphery of the inner flange  51  including the horizontal and vertical directions. In this embodiment, 4 or more holes with the same diameter are not continuously arranged in the peripheral direction and the bolt clamping force is evenly applied. 
     When a gas insulated switchgear is to be assembled, the insulating spacer  12  is provided between the outer flange  47  and the inner flange  51  and M16 closed-end bolts  56  are screwed into the tapped holes  52  made in  16  positions on the periphery of the inner flange  51  from the side of the outer flange  47 . By this procedure, it is possible to provide the insulating spacer  12  between the outer flange  47  and the inner flange  51  and connect the bus unit  1  to the breaker unit  2 . 
     The unit dismantling procedure at the time of maintenance and inspection or trouble recovery is shown in FIGS. 4 and 5. FIG. 4 shows a case that the units are dismantled in the state that the insulating spacer  12  is attached to the outer flange  47  of the bus enclosure  7  and FIG. 5 shows a case that the units are dismantled in the state that the insulating spacer  12  is attached to the inner flange  51  of the breaker enclosure  16 . Before starting dismantling of the units, the insulating gas in the unit to which the insulating spacer  12  is not to be attached is collected and the pressure of insulating gas in the unit to which the insulating spacer  12  is to be attached is reduced. 
     When dismantling the units in the state that the insulating spacer  12  is attached to the outer flange  47  of the bus enclosure  7 , the M16 closed-end bolts  56  clamped in the horizontal and vertical 4 positions are removed first. Next, assuming the thickness of the outer flange  47  as L1 and the thickness of the insulating spacer  12  as L2, M20 closed-end bolts  57  about L1+½×L2 in length are screwed into the portions where the M16 closed-end bolts  56  are removed from the side of the outer flange  47  and the insulating spacer  12  is attached to the outer flange  47 . 
     In this case, depending on the position of the M20 closed-end bolts  57  for connecting the outer flange  47  to the insulating spacer  12 , the position of M20 tapped holes  54  to be provided in the insulating spacer  12  and the position of idle holes  48  for M20 bolts to be provided in the outer flange  47  are decided. However, in this case, the horizontal and vertical positions are set as an example. Next, the M16 closed-end bolts  56  in the 12 positions other than the aforementioned 4 positions are removed. By this series of procedures, the bus unit  1  and the breaker unit  2  can be separated in the state that the insulating spacer  12  is attached to the outer flange  47 . 
     When dismantling the units in the state that the insulating spacer  12  is attached to the inner flange  51  of the breaker enclosure  16 , the M16 closed-end bolts  56  in the 4 positions at 45° from the horizontal and vertical directions are removed first. Next, a bolt  58  having a step  59  in which an M16 tapped part is formed at one end and a part of the column is machined flat at the other end is screwed into the portion where the M16 closed-end bolt  56  is removed from the side of the outer flange  47 . In this case, the insulating spacer  12  is attached to the inner flange  51  by the step  59 . Next, the M16 closed-end bolts  56  in the  12  positions other than the aforementioned 4 positions are removed. By this series of procedures, the bus unit  1  and the breaker unit  2  can be separated in the state that the insulating spacer  12  is attached to the inner flange  51 .