Switchgear

Abstract

To provide a switchgear capable of suppressing destruction of an insulation mold.SOLUTION: A switchgear 1 comprises: a housing 2 in which an insulation gas is encapsulated; a switch 5 which is stored in the housing 2; a primary-side cable head which is electrically connected to a primary side of the switch 5 via a primary-side lead wire and to which a power receiving side bus is connected; a secondary-side cable head 42 which is electrically connected to a secondary side of the switch 5 via a secondary-side lead wire 62 and to which a transformer side bus 102 is connected; a tapered insulation mold 72 which is provided in a connection part of the secondary-side lead wire 62 and the secondary-side cable head 42 and is formed of an insulation material, and whose outer diameter is increased gradually toward the secondary-side cable head 42; and a shield part 8 which is provided at a side separated from the secondary-side cable head 42 with respect to the insulation mold 72 and is formed of a conductive material, and whose diameter is expanded radially outside from an outer peripheral surface of the secondary-side lead wire 62.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a switching device. [Background technology]

[0002] A gas-insulated switchgear installed in a substation or the like is disclosed that includes a circuit breaker (see, for example, Patent Document 1). The circuit breaker cuts off an electric circuit between the power receiving side (primary side) and the transformer side (secondary side) when lightning strikes or the like. The circuit breaker is filled with insulating gas such as sulfur hexafluoride (SF6) and is housed in a circuit breaker unit made of a conductive material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-112661 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a gas-insulated switchgear as disclosed in Patent Document 1, the circuit breaker unit itself is made of metal and is electrically grounded to a grounding device buried in the ground or the like. The primary and secondary busbars are each connected to a cable head outside the circuit breaker unit. The cable head and the circuit breaker are connected via a conductor that penetrates a part of the circuit breaker unit. An insulating mold is provided at the connection between the cable head and the conductor. The insulating mold electrically insulates the cable head and the conductor from the circuit breaker unit. The insulating mold is formed in a tapered shape whose outer diameter gradually increases as it approaches the cable head in the extension direction of the conductor.

[0005] When a circuit breaker cuts off the path of an excessively large fault current caused by a lightning strike or other event between the primary and secondary sides, an arc may occur inside the circuit breaker unit. This arc causes a chemical reaction in the insulating gas inside the circuit breaker unit, generating decomposition gases containing substances such as hydrogen fluoride (HF) and sulfur dioxide (SO2) inside the circuit breaker unit. If the generated decomposition gas comes into contact with the insulating mold, it may cause the insulating material (resin material) that makes up the insulating mold to deteriorate, leading to a decrease in insulating performance.

[0006] Furthermore, when a high voltage is applied to an insulating mold in which the insulating material has deteriorated in this way, such as during a lightning strike, the boundary between the insulating mold, the conductor, and the insulating gas in the circuit breaker unit becomes an electrically weak point. Then, when a high voltage is applied, such as during a lightning strike, an electrical short circuit (flashover) occurs along the surface of the insulating mold between the conductor on the high voltage side and the circuit breaker unit on the ground side, starting from the boundary between the insulating mold, the conductor, and the insulating gas, which may lead to the destruction of the insulating mold.

[0007] In view of the above circumstances, an object of the present invention is to provide a switchgear capable of suppressing damage to an insulating mold even when the insulating mold is deteriorated. [Means for solving the problem]

[0008] A switchgear according to an embodiment of the present invention includes a housing filled with insulating gas and formed of a conductive material, a switch accommodated in the housing, a primary side cable head electrically connected to the primary side of the switch via a primary side conductor and to which a receiving side busbar is connected, a secondary side cable head electrically connected to the secondary side of the switch via a secondary side conductor and to which a transformer side busbar is connected, a tapered insulating mold provided at the connection between the secondary side conductor and the secondary side cable head, formed of an insulating material and having an outer diameter gradually increasing as it approaches the secondary side cable head in the extension direction of the secondary side conductor, and a shield portion provided on the side of the insulating mold away from the secondary side cable head in the extension direction of the secondary side conductor, formed of a conductive material, and expanding radially outward from the outer circumferential surface of the secondary side conductor.

[0009] The shielding portion may have a first plane facing the secondary cable head side in the extension direction of the secondary conductor and intersecting with the extension direction of the secondary conductor, and a second plane facing a side away from the secondary cable head in the extension direction of the secondary conductor and intersecting with the extension direction of the secondary conductor, and the thickness in the extension direction of the secondary conductor may be constant in the radial direction. The shielding portion may be formed in a circular shape when viewed from the extension direction of the secondary conductor. The outer peripheral edge portion of the shielding portion may have an arc-shaped cross-sectional shape that is convex outward in the radial direction.

[0010] The shielding portion may have a convex curved surface that protrudes toward the secondary cable head in the extension direction of the secondary conductor. The shielding portion may have an outer diameter larger than a minimum diameter portion of the insulating mold. The shielding portion may have an outer diameter larger than a maximum diameter portion of the insulating mold.

[0011] The secondary cable head may be connectable to an end of the transformer busbar. A plurality of sets of secondary conductors, insulating molds, and shielding parts may be provided, and the shielding parts of the plurality of sets may be arranged at intervals in the radial direction. The switch may be a circuit breaker. The inside of the housing may be divided into a plurality of chambers, and the shielding part may be provided in one of the plurality of chambers that houses the circuit breaker. Effect of the Invention

[0012] In the switchgear according to the embodiment of the present invention, the shield portion provided on the side of the insulating mold away from the secondary cable head is made of a conductive material and expands radially outward from the outer circumferential surface of the secondary conductor, so that in the event of a lightning strike, an electrical short circuit occurs between the shield portion that expands radially outward and the maximum diameter portion of the insulating mold. As a result, the occurrence of an electrical short circuit along the surface of the insulating mold can be suppressed, and the insulating mold can be prevented from being destroyed.

[0013] In addition, in a configuration in which the thickness of the shielding portion is constant in the radial direction, the distance between the second plane and the insulating mold in the extension direction of the secondary conductor is ensured, and electrical short circuits along the surface of the insulating mold can be effectively suppressed. In a configuration in which the shielding portion is formed in a circular shape, electrical short circuits along the surface of the insulating mold can be effectively suppressed at any position in the circumferential direction of the shielding portion. In a configuration in which the outer peripheral edge of the shielding portion has an arc-shaped cross-sectional shape that is convex outward in the radial direction, the presence of acute-angled protruding portions on the outer peripheral edge of the shield can be suppressed, and electrical short circuits along the surface of the insulating mold can be suppressed.

[0014] Also, even in a configuration in which the shield portion has a convex curved surface that protrudes toward the secondary cable head, electrical short circuits along the surface of the insulating mold can be effectively suppressed. Furthermore, in a configuration in which the shield portion has an outer diameter larger than the minimum diameter portion of the insulating mold, a gap between the shield portion and the insulating mold can be secured, making it difficult for electrical short circuits to occur along the surface of the insulating mold. Furthermore, in a configuration in which the shield portion has an outer diameter larger than the maximum diameter portion of the insulating mold, a larger gap between the shield portion and the insulating mold can be secured, making it even more difficult for electrical short circuits to occur along the surface of the insulating mold.

[0015] In addition, in a configuration in which the secondary cable head can be connected to an end of a transformer busbar, an insulating mold provided between a secondary cable head to which an end of the transformer busbar is connected and a connection portion with a secondary conductor can be prevented from causing an electrical short circuit along the surface of the insulating mold, thereby preventing the insulating mold from being destroyed. In addition, in a configuration in which a plurality of sets of secondary conductors, insulating molds, and shielding portions are provided, the plurality of sets of shields are arranged at intervals in the radial direction, thereby preventing an electrical short circuit between the plurality of sets of shields. In addition, in a configuration in which the switch is a circuit breaker, an arc generated when the circuit breaker cuts off the path generates decomposition gas from the insulating gas in the unit, which easily deteriorates the molded resin of the insulating mold. By preventing an electrical short circuit along the surface of the insulating mold, it is possible to prevent the insulating mold from being destroyed due to deterioration of the molded resin. In addition, in a configuration in which the shielding portion is provided in the chamber that houses the circuit breaker among the multiple chambers in the housing, the shielding portion is provided in the chamber in which a large amount of decomposition gas is generated by the arc that occurs when the circuit breaker breaks the electric path between the primary side and the secondary side. As a result, even if the insulation mold is deteriorated by the decomposition gas, the shielding portion can prevent electrical short circuits from occurring along the surface of the insulation mold and prevent destruction of the insulation mold. [Brief description of the drawings]

[0016] [Figure 1] FIG. 2 is a diagram showing the appearance of a switching device according to an embodiment, as viewed from a secondary-side cable head side. [Diagram 2] 2 is a cross-sectional view of the internal structure of the switchgear of FIG. 1, seen from the opposite side to the secondary cable head. [Diagram 3] FIG. 3 is a cross-sectional view taken along the line II in FIG. 2. [Figure 4] 3 is a cross-sectional view of the first unit as viewed from the right side of FIG. 2. [Diagram 5] 13 is a perspective view showing a secondary insulating mold and a shield portion provided at a connection portion between a secondary conductor and a secondary cable head. FIG. [Figure 6]4 is a cross-sectional view showing a secondary insulating mold and a shield portion provided at a connection portion between a secondary conductor and a secondary cable head. FIG. [Figure 7] FIG. 13 is a diagram showing an electric field distribution during a lightning strike or the like in a configuration that does not include a shield portion for comparison. [Figure 8] FIG. 13 is a diagram showing a predicted flashover path in a configuration that does not include a shield portion for comparison. [Figure 9] 4A to 4C are diagrams illustrating electric field distribution during a lightning strike or the like in the switching device of the present embodiment. [Figure 10] FIG. 2 is a diagram showing a predicted flashover path in the switchgear of the present embodiment. [Figure 11] 13 is a cross-sectional view showing a secondary insulating mold and a shield portion provided at a connection portion between a secondary conductor and a secondary cable head according to a modified example of the embodiment. FIG. [Figure 12] 13A and 13B are diagrams illustrating an electric field distribution during a lightning strike or the like in a switching device according to a modified example of the embodiment. [Figure 13] FIG. 11 is a diagram showing a predicted flashover path in a switching device according to a modified example of the embodiment. [Figure 14] FIG. 13 is a diagram showing the results of checking whether or not a secondary insulating mold is broken when a voltage is applied to the secondary insulating mold after it has been exposed to a decomposition gas. [Figure 15] 1 is a graph for comparing the measurement results of electrical resistance between a pre-test sample before exposure to decomposition gases and a post-test sample after exposure to decomposition gases and application of a voltage. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. However, the present invention is not limited to the contents described below. In addition, in order to explain the embodiment in the drawings, some parts are enlarged or emphasized, and the scale is appropriately changed to express it, and the dimensions and shape may differ from those of the actual product. FIG. 1 is a view of the appearance of a switching device 1 according to the embodiment, seen from the secondary side cable head 42 side. FIG. 2 is a cross-sectional view of the internal structure of the switching device 1 of FIG. 1, seen from the opposite side to the secondary side cable head 42. FIG. 3 is a cross-sectional view taken along the arrow II in FIG. 2.

[0018] A switchgear 1 according to this embodiment is installed in a substation or the like, and interrupts a fault current by interrupting an electric path between a primary power receiving busbar 101 and a secondary transformer busbar 102 when lightning strikes or the like. As shown in Fig. 1, the switchgear 1 has a first unit 20 and a second unit 30. The first unit 20 and the second unit 30 are connected to each other.

[0019] 2 and 3, the switchgear 1 includes a housing 2, a primary side cable head 41, a secondary side cable head 42, a switch 5, a primary side conductor 61, a secondary side conductor 62, a primary side insulating mold 71, a secondary side insulating mold (insulating mold) 72, and a shield section 8. The housing 2 is provided on an installation surface G such as the ground via a stand 3. The housing 2 is formed from a conductive material such as steel.

[0020] The housing 2 has a first housing 21 and a second housing 31. The first housing 21 forms an outer shell of the first unit 20. The second housing 31 forms an outer shell of the second unit 30. The first housing 21 and the second housing 31 each have a hollow structure and have chambers S1 and S2 therein, which are sealed spaces. As shown in Fig. 2, the chamber S1 in the first housing 21 and the chamber S2 in the second housing 31 are separated by an insulating partition 23.

[0021] FIG. 4 is a cross-sectional view of the first unit 20 seen from the right side of FIG. 2. As shown in FIGS. 2 to 4, the first unit 20 accommodates the switch 5, a part of the primary conductor 61, the secondary conductor 62, the secondary insulating mold 72, the shield part 8, and the like in the first housing 21. The first housing 21 has a housing main body 24, a bottom plate part 25, and a top plate part 26. The housing main body 24 is formed in a cylindrical shape that is continuous in the vertical direction. For example, the cross-sectional shape of the housing main body 24 when viewed from the vertical direction is circular, and the housing main body 24 is open at the top and bottom. The bottom plate part 25 closes the opening at the lower end of the housing main body 24 from below. The top plate part 26 closes the opening at the upper end of the housing main body 24 from above. The bottom plate part 25 and the top plate part 26 are each detachably flange-connected to the housing main body 24 by a plurality of bolts.

[0022] A first opening 27 and a second opening 28 are formed in the housing body 24. The first opening 27 and the second opening 28 each penetrate the cylindrical housing body 24 in the radial direction. As shown in Figs. 2 and 3, the outer peripheral edge of the first opening 27 is flange-connected to the outer peripheral edge of an opening 31h formed in the second housing 31 by a plurality of bolts (not shown). The first opening 27 and the opening 31h are separated by a partition 23.

[0023] As shown in Figs. 1 to 4, the second opening 28 is formed in the upper part of the housing body 24. When viewed from the top-bottom direction, the second opening 28 opens in a direction different from the first opening 27 in the circumferential direction around the center of the housing body 24. The second opening 28 is closed by a lid body 29. The lid body 29 is formed from a metal material such as iron. The lid body 29 is flange-connected to the outer periphery of the second opening 28 by a plurality of bolts (not shown).

[0024] As shown in FIG. 2, the second unit 30 accommodates the disconnector 9 and the like in the second housing 31. The second housing 31 has a housing body 32, a bottom plate portion 33, and a top plate portion 34. The housing body 32 is formed in a cylindrical shape that is continuous in the vertical direction. The housing body 32 has, for example, a circular cross-sectional shape when viewed from the vertical direction, and is open at the top and bottom. The bottom plate portion 33 closes the opening at the lower end of the housing body 32 from below. The top plate portion 34 closes the opening at the upper end of the housing body 32 from above. The bottom plate portion 33 and the top plate portion 34 are each detachably flange-connected to the housing body 32 by a plurality of bolts.

[0025] The first housing 21 and the second housing 31 are each electrically grounded to a grounding device (not shown) buried in an installation surface G such as the ground. As a result, the first housing 21 and the second housing 31 are at ground potential. An insulating gas is sealed in the chambers S1 and S2 of the first housing 21 and the second housing 31, respectively. An example of the insulating gas used here is sulfur hexafluoride (SF6). The housing 2 may also have a third housing that houses a device for connecting to another switchgear, for example.

[0026] As shown in Figs. 1 and 2, a power receiving busbar 101 is connected to the primary cable head 41. The primary cable head 41 is formed in a cylindrical shape extending in the vertical direction. The primary cable head 41 is provided, for example, so as to contact the bottom plate portion 33 of the second housing 31 from below. The primary cable head 41 is exposed to the outside of the second housing 31. An end of the power receiving busbar 101 located outside the second housing 31 is connected to the primary cable head 41. Three sets of primary cable heads 41 are provided for three phases.

[0027] As shown in Figures 1, 3 and 4, the secondary cable head 42 is connected to the transformer busbar 102. The secondary cable head 42 is exposed to the outside of the first housing 21. The secondary cable head 42 is provided so as to be in contact with the cover 29 in the horizontal direction. An end of the transformer busbar 102 located outside the first housing 21 is connected to the secondary cable head 42. The primary cable head 41 is provided for three phases, i.e., three sets.

[0028] 4, the secondary-side cable head 42 integrally includes a head first portion 42a extending horizontally from the cover 29 and intersecting with the surface 29f of the cover 29, and a head second portion 42b extending downward from the head first portion 42a. The transformer-side busbar 102 is inserted into the head second portion 42b from below, and can be electrically connected to a busbar connection terminal (not shown) provided in the head second portion 42b.

[0029] As shown in Figs. 2 to 4, the switch 5 is accommodated in the first housing 21. In this embodiment, the switch 5 is a circuit breaker 5S capable of breaking an electric circuit between the primary side and the secondary side. The switch 5 (circuit breaker 5S) is provided for three phases, i.e., three sets. As shown in Fig. 2, one end of a primary side conductor 61 is connected to the primary side of the circuit breaker 5S of each phase. That is, the primary side conductor 61 is also provided for three phases, i.e., three sets.

[0030] One end of the secondary conductor 62 is connected to the secondary side of the circuit breaker 5S of each phase. That is, three sets of secondary conductors 62 are provided for three phases. The other end of the secondary conductor 62 passes through the cover 29 and is electrically connected to a conductor connection terminal provided in the head first portion 42a of the secondary cable head 42. As a result, the secondary side of the circuit breaker 5S is electrically connected to the transformer bus 102 via the secondary conductor 62 and the secondary cable head 42.

[0031] 2, the primary conductor 61 passes through the partition portion 23 and is led from inside the first housing 21 to inside the second housing 31. A disconnector 9 is provided midway along the primary conductor 61. The other end of the primary conductor 61 passes through the bottom plate portion 33 and is connected to the primary cable head 41. As a result, the primary side of the circuit breaker 5S is electrically connected to the primary cable head 41 via the primary conductor 61.

[0032] The primary insulating mold 71 is provided at a connection portion between the primary conductor 61 and the primary cable head 41. The primary insulating mold 71 is disposed inside the second housing 31 with respect to the bottom plate portion 33. In this embodiment, the primary insulating mold 71 is formed of epoxy resin filled with granular silica. As described above, the primary conductor 61, which penetrates the bottom plate portion 33 and is connected to the primary cable head 41, penetrates the primary insulating mold 71 in the extension direction (up and down direction) of the primary conductor 61.

[0033] Fig. 5 is a perspective view showing the secondary insulating mold 72 provided at the connection portion between the secondary conductor 62 and the secondary cable head 42, and the shield portion 8. Fig. 6 is a cross-sectional view showing the secondary insulating mold 72 provided at the connection portion between the secondary conductor 62 and the secondary cable head 42, and the shield portion 8. As shown in Figs. 3 to 6, the secondary insulating mold 72 is provided at the connection portion between the secondary conductor 62 and the secondary cable head 42. The secondary insulating mold 72 is disposed inside the first housing 21 with respect to the cover 29.

[0034] The secondary insulating mold 72 is made of an insulating material such as epoxy resin. In this embodiment, the secondary insulating mold 72 is made of epoxy resin filled with granular silica. The secondary conductor 62, which penetrates the cover 29 and is connected to the secondary cable head 42 as described above, penetrates the secondary insulating mold 72 in the extension direction (horizontal direction) of the secondary conductor 62.

[0035] The secondary insulating mold 72 is formed in a tapered shape (frustum shape) in which the outer diameter gradually increases toward the secondary cable head 42 in the extension direction of the secondary conductor 62. As shown in Fig. 6, the secondary insulating mold 72 has a first end face 72a, a second end face 72b, and an outer circumferential surface 72c. The first end face 72a and the second end face 72b are each formed along a plane intersecting the extension direction of the secondary conductor 62.

[0036] The first end face 72a is formed on a side away from the cover 29 in the extension direction of the secondary conductor 62. The second end face 72b is formed on a side facing the cover 29 in the extension direction of the secondary conductor 62. The second end face 72b abuts against the cover 29. As a result, the cover 29 is sandwiched between the secondary cable head 42 and the second end face 72b of the secondary insulating mold 72. Furthermore, a protrusion 72d that is inserted into a through hole 29h formed in the cover 29 is integrally provided at the center of the second end face 72b.

[0037] The diameter of the first end face 72a is smaller than the diameter of the second end face 72b. The outer peripheral surface 72c is formed to connect the first end face 72a and the second end face 72b. The outer peripheral surface 72c gradually expands in diameter from the first end face 72a side toward the second end face 72b side. That is, in the extension direction of the secondary side conductor 62, the end of the outer peripheral surface 72c on the first end face 72a side is the minimum diameter portion 72s of the secondary side insulating mold 72, and the end on the second end face 72b side is the maximum diameter portion 72m of the secondary side insulating mold 72.

[0038] The shielding portion 8 is provided at the connection portion between the secondary cable head 42 and the secondary conductor 62. The shielding portion 8 is provided on the side of the secondary insulating mold 72 that is away from the secondary cable head 42 in the extension direction of the secondary conductor 62. The shielding portion 8 is made of a conductive material such as aluminum. The shielding portion 8 expands in diameter from the outer circumferential surface 62f of the secondary conductor 62 toward the outside in the radial direction centered on the secondary conductor 62.

[0039] The shield portion 8 is formed, for example, in a circular shape when viewed from the extension direction of the secondary conductive wire 62. In this embodiment, the shield portion 8 has a thickness T in the extension direction of the secondary conductive wire 62 that is constant in the radial direction of the shield portion 8. That is, in this embodiment, the shield portion 8 is formed, for example, in a disk shape. The shield portion 8 has a first plane 81, a second plane 82, and an outer circumferential edge portion 83.

[0040] The first plane 81 and the second plane 82 are formed along a plane intersecting the extension direction of the secondary conductor 62. The first plane 81 faces the secondary cable head 42 side in the extension direction of the secondary conductor 62. The second plane 82 faces a side away from the secondary cable head 42 in the extension direction of the secondary conductor 62. The first plane 81 and the second plane 82 are formed parallel to each other. As a result, the thickness T of the shield part 8 in the extension direction of the secondary conductor 62 is constant in the radial direction. In this embodiment, the radius r of the end face of the shield part 8 is preferably 10±2 mm (i.e., the thickness T is about 16 mm to 24 mm).

[0041] The outer peripheral edge portion 83 faces radially outward in the shield portion 8. The outer peripheral edge portion 83 connects the outer peripheral edge of the first plane 81 and the outer peripheral edge of the second plane 82. In this embodiment, the outer peripheral edge portion 83 has an arc-shaped cross-sectional shape that is convex radially outward. In this embodiment, the shield portion 8 is formed by a smooth continuous surface without corners, even at the connection portion between the outer peripheral edge portion 83 and the first plane 81 and the connection portion between the outer peripheral edge portion 83 and the second plane 82.

[0042] The shield part 8 has an outer diameter larger than the minimum diameter part 72s of the secondary insulating mold 72. Furthermore, the shield part 8 preferably has an outer diameter larger than the maximum diameter part 72m of the secondary insulating mold 72. The shield part 8 may have an outer diameter equal to the maximum diameter part 72m of the secondary insulating mold 72. The shield part 8 may have an outer diameter smaller than the maximum diameter part 72m of the secondary insulating mold 72, but in order to effectively exert the function of the shield part 8 described later, it is preferable that the outer diameter is as large as possible. In this embodiment, the shield part 8 has an outer diameter that is, for example, about 1.2 to 2.5 times, or about 1.5 to 2.0 times, the outer diameter of the maximum diameter part 72m of the secondary insulating mold 72, but is not limited to this form.

[0043] 2 and 4, the shield parts 8 provided on the three sets of secondary conductors 62 for each phase provided in the first housing 21 are disposed at a radial distance of at least a predetermined distance. This prevents electrical short circuits from occurring between the shield parts 8 for each phase. In order to ensure a distance between the shield parts 8 for each phase, for example, the positions of the shield parts 8 for each phase may be shifted in the extension direction of the secondary conductor 62.

[0044] Here, in this embodiment, the shielding portion 8 is provided only in the first housing 21 in which the circuit breaker 5S is accommodated. When the circuit breaker 5S breaks the electric path between the primary side and the secondary side, the current value interrupted by the circuit breaker 5S is, for example, 25 kA. In contrast, as described above, the current value in the first housing 21 connected to the grounding device is, for example, about 400 A. As a result, a powerful arc is likely to occur in the first housing 21 when the circuit breaker 5S breaks the electric path. Then, the generated arc decomposes the insulating gas (SF6) in the first housing 21, and the amount of decomposition gas generated increases. As a result, deterioration of the mold resin forming the secondary side insulating mold 72 exposed to the decomposition gas in the first housing 21 is likely to be accelerated.

[0045] In contrast, since the circuit breaker 5S is not housed in the second housing 31, generation of decomposition gas due to arcing is suppressed. Therefore, in the primary side insulating mold 71 arranged in the second housing 31, deterioration of the mold resin due to decomposition gas is unlikely to occur, and there is little need to provide a shield section 8. Of course, the shield section 8 may also be provided near the primary side insulating mold 71 arranged in the second housing 31.

[0046] Fig. 7 is a diagram showing an electric field distribution during a lightning strike or the like in a configuration that does not include a shielding portion for comparison. Fig. 8 is a diagram showing an expected flashover path in a configuration that does not include a shielding portion for comparison. Here, for comparison, a case where no shielding portion 8 is provided (corresponding to a conventional configuration) will be considered as shown in Figs. 7 and 8. When no shielding portion 8 is provided, a high electric field occurs during a lightning strike or the like from region A1 along the surface of the secondary conductor 62 to region A2 along the outer circumferential surface 72c of the secondary insulating mold 72.

[0047] In this case, if the mold resin of the secondary insulating mold 72 is deteriorated by the decomposition gas generated in the first housing 21, when a flashover occurs during a lightning strike or the like, the flashover current is expected to start at the boundary portion K between the secondary conductor 62, the secondary insulating mold 72, and the insulating gas (decomposition gas), and follow a path R1 along the outer circumferential surface 72c (creepage) from the minimum diameter portion 72s to the maximum diameter portion 72m of the secondary insulating mold 72. As a result, the entire outer circumferential surface 72c of the secondary insulating mold 72 may be destroyed along the predicted flashover path.

[0048] Fig. 9 is a diagram showing an electric field distribution in the switchgear of this embodiment during a lightning strike, etc. Fig. 10 is a diagram showing a predicted flashover path in the switchgear of this embodiment. In contrast, as shown in Fig. 9, when a shield section 8 is provided, a high electric field is generated in region A3 near the outer peripheral edge section 83 of the shield section 8 and in region A4 near the maximum diameter section 72m of the secondary side insulating mold 72 during a lightning strike, etc.

[0049] In this case, if the mold resin of the secondary insulating mold 72 is deteriorated by the decomposition gas, as shown in Fig. 10, a flashover current in the event of a lightning strike or the like is expected to follow a linear path R2 along the extension direction of the secondary conductor 62 from the outer peripheral edge 83 of the shielding portion 8 to the maximum diameter portion 72m of the outer peripheral surface 72c of the secondary insulating mold 72. In other words, since a flashover is likely to occur at the closest distance from the high electric field portion of the shielding portion 8 (near the apex of the semicircular portion in cross section of the end portion) to the vicinity of the high electric field (outer peripheral surface 72c), the flashover current is expected to follow path R2. In this case, the flashover current is prevented from flowing along the outer peripheral surface 72c of the secondary insulating mold 72, and destruction of the secondary insulating mold 72 is prevented.

[0050] Thus, in the switchgear 1 according to this embodiment, the shield portion 8 expands radially outward from the outer circumferential surface of the secondary conductor 62. As a result, even if the molded resin forming the secondary insulating mold 72 has deteriorated due to decomposition gas, when a flashover occurs due to a lightning strike or the like, a flashover current is prevented from flowing along the outer circumferential surface 72c (creeping surface) of the secondary insulating mold 72, and damage to the secondary insulating mold 72 can be prevented.

[0051] Furthermore, since the thickness T of the shield portion 8 is constant in the radial direction, the distance between the second plane 82 and the secondary insulating mold 72 in the extension direction of the secondary conductor 62 is ensured, and electrical short circuits along the creeping surface of the secondary insulating mold 72 can be effectively suppressed. Furthermore, since the shield portion 8 is formed in a circular shape, electrical short circuits along the creeping surface of the secondary insulating mold 72 can be effectively suppressed at any position in the circumferential direction of the shield portion 8. Furthermore, since the outer peripheral edge portion 83 of the shield portion 8 has an arc-shaped cross-sectional shape that is convex outward in the radial direction, the presence of acute-angled protruding portions on the outer peripheral edge portion 83 of the shield can be suppressed, and electrical short circuits along the creeping surface of the secondary insulating mold 72 can be suppressed.

[0052] In addition, since the shielding part 8 has an outer diameter larger than the minimum diameter part 72s of the secondary insulating mold 72, the interval between the shielding part 8 and the outer peripheral surface 72c of the secondary insulating mold 72 can be secured, and an electrical short circuit along the creeping surface of the secondary insulating mold 72 can be made less likely to occur. In addition, since the shielding part 8 has an outer diameter larger than the maximum diameter part 72m of the secondary insulating mold 72, the interval between the shielding part 8 and the secondary insulating mold 72 can be secured larger, and an electrical short circuit along the creeping surface of the secondary insulating mold 72 can be made less likely to occur. In addition, since the secondary cable head 42 can be connected to the end of the transformer side busbar 102, the secondary insulating mold 72 provided between the connection part between the secondary cable head 42 to which the end of the transformer side busbar 102 is connected and the secondary conductor 62 can be prevented from causing an electrical short circuit along the creeping surface of the secondary insulating mold 72, and the destruction of the secondary insulating mold 72 can be prevented.

[0053] In addition, since the sets of shielding parts 8 are arranged at intervals in the radial direction, it is possible to prevent electrical short-circuiting between the sets of shielding parts 8. In addition, since the switch 5 is a circuit breaker 5S, in the secondary insulating mold 72 provided together with the circuit breaker 5S that cuts off the primary side and the secondary side in a current-carrying state, it is possible to prevent electrical short-circuiting along the creeping surface of the secondary insulating mold 72 and prevent damage to the secondary insulating mold 72. In addition, since the shielding part 8 is provided in the chamber S1 in which the circuit breaker 5S is accommodated, among the multiple chambers S1 and S2 in the housing 2, even if the secondary insulating mold 72 is deteriorated by decomposition gas, it is possible to prevent electrical short-circuiting along the creeping surface of the secondary insulating mold 72 and prevent damage to the secondary insulating mold 72.

[0054] (Modification of the embodiment) In the above embodiment, the shielding portion 8 is disk-shaped having the first plane 81 and the second plane 82, but is not limited thereto. Fig. 11 is a cross-sectional view showing the secondary insulating mold 72 and the shielding portion 8B according to a modified example of this embodiment. For example, the switchgear 1 may be provided with a shielding portion 8B as shown in Fig. 11. This shielding portion 8B has a convex curved surface 85 facing the secondary cable head 42 in the extension direction of the secondary conductor 62. The convex curved surface 85 protrudes in a substantially hemispherical shape toward the secondary cable head 42 in the extension direction of the secondary conductor 62.

[0055] Fig. 12 is a diagram showing an electric field distribution during a lightning strike or the like in a switching device according to a modification of this embodiment. Fig. 13 is a diagram showing an expected flashover path in a switching device according to a modification of this embodiment. As shown in Fig. 12, when a shield part 8B having a convex curved surface 85 is provided, a high electric field is generated in an area A5 covering the entire convex curved surface 85 and an area A6 in the vicinity of the maximum diameter part 72m of the secondary side insulating mold 72 during a lightning strike or the like.

[0056] In this case, if the mold resin of the secondary insulating mold 72 is deteriorated by the decomposition gas, as shown in Fig. 13, a flashover current during a lightning strike or the like is expected to flow uniformly along a path R3 along the extension direction of the secondary conductor 62 from the entire convex curved surface 85 of the shielding portion 8 to the outer peripheral surface 72c of the secondary insulating mold 72. In other words, since a flashover is likely to occur at the closest distance from the high electric field portion of the shielding portion 8B (near the outer surface of the convex curved surface 85) to the vicinity of the high electric field (the outer peripheral surface 72c), the flashover is expected to follow the path R3. In this case as well, the flashover current is prevented from flowing along the outer peripheral surface 72c of the secondary insulating mold 72, and the destruction of the secondary insulating mold 72 is prevented.

[0057] In the above embodiment and modified example, the circuit breaker 5S is exemplified as the switch 5, but this is not limiting. In the above embodiment, the shielding portion 8 is provided only in the vicinity of the secondary side insulating mold 72 provided in the first housing 21, but this is not limiting. For example, if the primary side insulating mold 71 is provided in the first housing 21 that accommodates the circuit breaker 5S, the shielding portion 8 may be provided in the vicinity of the primary side insulating mold 71 in a similar manner.

[0058] (Verification example) Next, the configuration of the above embodiment was verified, and the results are shown below. First, a flashover test was performed using the secondary insulating mold 72 in a state where the mold resin had not deteriorated due to exposure to decomposition gas. Here, epoxy resin filled with silica was used as the mold resin forming the secondary insulating mold 72.

[0059] In the flashover test, after applying voltages of 200kV, 300kV, 400kV, and 500kV, the presence or absence of destruction of the secondary insulating mold 72 due to flashover was confirmed. The above voltages were applied separately to the positive and negative electrodes. As a result, no destruction of the secondary insulating mold 72 was observed at voltages of 200kV, 300kV, 400kV, and 500kV in both the cases of application to the positive and negative electrodes.

[0060] Thereafter, the sealed space (corresponding to the chamber S1 of the first housing 21) containing the secondary insulating mold 72 and the circuit breaker 5S was filled with SF6 gas as an insulating gas, and a current of 25 kA was repeatedly interrupted six times by the circuit breaker 5S. Decomposition gas was generated from the insulating gas (SF6) by an arc generated when the circuit breaker 5S interrupted, and the secondary insulating mold 72 was exposed to the decomposition gas for three hours in the sealed space. It was confirmed that the decomposition gas contained a large amount of hydrogen fluoride, which is thought to have an adverse effect on the silica-filled epoxy resin that forms the secondary insulating mold 72.

[0061] Next, a voltage of 400 kV, which corresponds to lightning, was applied to the positive and negative electrodes three times each. After the application of the 400 kV voltage, no destruction was observed in the secondary insulating mold 72. Next, assuming that maintenance is performed after a lightning strike in an actual switchgear, the space in which the circuit breaker 5S is housed is opened, and the secondary insulating mold 72 is exposed to the atmosphere for 24 hours. After that, the space in which the secondary insulating mold 72 is housed is sealed again, and insulating gas (SF6) is refilled. Then, voltages of 200 kV, 300 kV, 400 kV, and 500 kV are applied to the positive and negative electrodes three times each, and the presence or absence of destruction of the secondary insulating mold 72 due to flashover is confirmed. FIG. 14 is a diagram showing the results of confirmation of the presence or absence of destruction when a voltage is applied to the secondary insulating mold after exposure to decomposition gas. As a result, as shown in FIG. 14, no destruction was observed in the secondary insulating mold 72 at each voltage.

[0062] The surface of secondary insulating mold 72 after the above test was observed using a scanning electron microscope (SEM). As a result, it was confirmed that multiple dents had formed on the surface of secondary insulating mold 72 after the test, whereas no noticeable irregularities were observed before the test. In addition, elemental analysis was performed on secondary insulating mold 72 before and after the test, and it was confirmed that fluorine atoms, which were not observed in secondary insulating mold 72 before the test, were detected in an amount equivalent to the insulating field after the test.

[0063] Furthermore, five samples were prepared for each of the secondary-side insulating mold 72 before and after the test, and the electrical resistance was measured. Fig. 15 is a graph for comparing the measurement results of the electrical resistance of the pre-test samples before exposure to the decomposition gas and the post-test samples after exposure to the decomposition gas and application of voltage. As a result, as shown in Fig. 15, it was found that the average electrical resistance of the secondary-side insulating mold 72 before the test was 1.34 x 1014 (Ω), while the average electrical resistance of the secondary-side insulating mold 72 after the test was 1.10 x 1014 (Ω), which is a slight decrease. [Explanation of symbols]

[0064] 1. Switchgear 2. Housing 5. Switch 5S circuit breaker 8, 8B: Shield section 41 Primary cable head 42 Secondary cable head 61 Primary conductor 62...Secondary conductor 71 Primary side insulation mold 72 Secondary side insulating mold (insulating mold) 72c...Outer surface 72m...Maximum diameter part 72s...Minimum diameter part 81...1st plane 82...2nd plane 83...Outer edge 85...Convex curved surface 101... Receiving bus 102 Transformer side busbar S1, S2...room T Thickness

Claims

1. a housing filled with an insulating gas and made of a conductive material; A switch accommodated in the housing; a primary side cable head electrically connected to the primary side of the switch via a primary side conductor and to which a power receiving side busbar is connected; a secondary cable head electrically connected to the secondary side of the switch via a secondary conductor and to which a transformer bus is connected; a tapered insulating mold provided at a connection portion between the secondary conductor and the secondary cable head, the tapered insulating mold being made of an insulating material and having an outer diameter gradually increasing toward the secondary cable head in an extension direction of the secondary conductor; a shield portion provided on a side of the insulating mold that is away from the secondary cable head in the extension direction of the secondary conductor, the shield portion being made of a conductive material and expanding radially outward from an outer circumferential surface of the secondary conductor.

2. The shield portion is a first plane that faces the secondary cable head in the extension direction of the secondary conductor and intersects with the extension direction of the secondary conductor; a second plane that faces a side away from the secondary cable head in the extension direction of the secondary conductor and intersects with the extension direction of the secondary conductor; The thickness of the secondary conductor in the extension direction is constant in the radial direction. The opening and closing device according to claim 1 .

3. The shield portion is formed in a circular shape when viewed from the extending direction of the secondary conductor. The opening and closing device according to claim 2 .

4. The outer peripheral edge portion of the shield portion has an arc-shaped cross-sectional shape that is convex outward in the radial direction. The opening and closing device according to claim 1 or 2.

5. The shield portion is The switching device according to claim 1 , further comprising a convex curved surface that protrudes toward the secondary cable head in the extending direction of the secondary conductor.

6. The shield portion has an outer diameter larger than a minimum diameter portion of the insulating mold. The opening and closing device according to claim 1 or 2.

7. The shield portion has an outer diameter larger than a maximum diameter portion of the insulating mold. The opening and closing device according to claim 6.

8. The secondary cable head is connectable to an end of the transformer busbar. The opening and closing device according to claim 1 .

9. A plurality of sets of the secondary conductor, the insulating mold, and the shield portion are provided, The pairs of shields are arranged at intervals in the radial direction. The opening and closing device according to claim 1 or 2.

10. The switch is a circuit breaker. The opening and closing device according to claim 1 or 2.

11. The housing is divided into a plurality of chambers, The shield portion is provided in the chamber in which the circuit breaker is accommodated, among the plurality of chambers. The opening and closing device according to claim 10.

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