JP4931395B2 - Insulation structure of electrical equipment and switchgear using the insulation structure - Google Patents

Description

  This invention is applied to, for example, electric power transmission / distribution and power receiving facilities, and is applied to an insulating structure of an electric device in which a main circuit device such as a switchgear is housed in a ground metal case, and the insulating structure is applied. It relates to the switchgear.

For example, as shown in FIG. 11A, an electrode 41 is a conventional technique for improving the insulation performance by relaxing the electric field of an electrode system that generates an unequal electric field in an electric device used in an insulating gas. An insulating layer having a thickness satisfying a predetermined withstand voltage in a portion having a maximum electric field of approximately equal to an equipotential line in the space up to an electrode portion having a value of 90% or less of the maximum electric field strength of the surface of the insulating layer An electric field relaxation device provided with an insulating shield 42 having an insulating layer surface formed in a shape is disclosed (see Patent Document 1).
Further, as shown in FIG. 11B, the electrode structure that forms an unequal electric field in an insulating gas at a low pressure has a curvature sufficiently larger than the electrode 43 in the vicinity of the electrode 43 on the side where the electric field strength is large. An electric field relaxation device is disclosed in which a bowl-shaped insulating barrier 44 is inserted with a recess facing the electrode 43 (see Patent Document 2).

JP-A-2-151215 (first page, FIG. 1) JP-A-2-164209 (first page, FIG. 2)

  In electrical equipment such as gas-insulated switchgears, the need for compactness, weight reduction, and cost reduction has become stronger in recent years in order to cope with rising land prices and intense price competition at installation locations. Therefore, further advancement has been demanded in the insulation technology of electric equipment. In particular, in the field of gas insulated switchgear, dry air or nitrogen gas that does not cause global warming has been used in place of the conventional insulating medium SF6 gas. However, the dielectric strength of these gases is SF6. As low as about one third of the gas. For this reason, high performance of gas / solid composite insulation using an insulation coating or an insulation barrier is required. For example, an electric field relaxation technique using an insulation coating or an insulation barrier as described in the above-mentioned patent document has been proposed.

  However, in the conventional insulating structures shown in Patent Document 1 and Patent Document 2, the effective area of the insulator surface (details will be described later) may not always be minimized. In addition, the maximum electric field generated on the insulator surface may not be minimized. That is, considering the area effect characteristics described later, the conventional technique has a problem that the withstand voltage may not be expected to increase. For this reason, in particular, when applied to recent gas-insulated electrical equipment using air / nitrogen with low withstand voltage performance instead of SF6 gas, there is a problem that the electrical equipment is not sufficiently compacted and economically improved. It was.

  The present invention has been made to solve the above-described problems, and the withstand voltage performance can be improved by devising the shape of an insulating layer or an insulating barrier inserted between conductors of an electric device. It is an object of the present invention to obtain an insulating structure of an electric device and a switchgear using the insulating structure.

The electrical equipment insulation structure according to the present invention is an electrical equipment insulation structure in which a switchgear and its main circuit conductor are housed in a ground metal case and insulates between opposing conductors, and forms a local high electric field among the conductors. An insulating barrier is disposed in the vicinity of the conductor side forming a local high electric field between the two conductors of the conductor and the opposing conductor, the surface shape of the insulating barrier facing the opposing conductor is formed in a substantially plane, and The thickness of the insulating barrier is formed so as to continuously increase from the portion located at the shortest portion between the two conductors as it moves outward in the direction parallel to the substantially flat portion of the insulating barrier .

The switchgear according to the present invention is a switchgear in which a switchgear and its main circuit conductor are housed in a grounded metal case, between the electrodes of the switchgear, between phases of the main circuit conductor, or between the main circuit conductor and the grounded metal case. An insulating barrier is disposed in the vicinity of the conductor side forming the local high electric field between the two conductors of the conductor forming the local high electric field between the conductors facing each other, and the side facing the counter conductor The surface shape of the insulation barrier is formed in a substantially flat surface, and the thickness of the insulation barrier is continuous as the distance from the opposing conductor is away from the portion located in the shortest part to the outside in the direction parallel to the substantially planar portion of the insulation barrier. It is formed to be thick.

According to the insulating structure of the electric device of the present invention, the conductor side that forms a local high electric field between the two conductors, that is, the conductor that forms a local high electric field between the conductors facing each other inside the electric device. near the isolation barrier is disposed of, the surface shape of the side of the isolation barrier facing the opposing conductor is formed in the schematic plan and the thickness of the insulating barrier, the insulating barrier from site located shortest portion between the two conductors Since the thickness increases continuously with increasing distance from the substantially flat portion to the outer side in the parallel direction, the effective area of the insulating barrier surface is reduced and the breakdown electric field value of the insulating barrier surface is increased, so that the dielectric strength can be improved. Accordingly, the electric device can be reduced in size.
Furthermore, in the switchgear to which this structure is applied, the breakdown electric field value on the surface of the insulating barrier is increased, and the dielectric strength of the conductor portion using the insulating barrier is improved, so that it is possible to provide a switchgear with improved withstand voltage performance. it can.

Embodiment 1 FIG.
Hereinafter, an insulating structure of an electric device according to Embodiment 1 of the present invention will be described with reference to the drawings. First, as an example of an electrical apparatus in which the insulating structure of the present invention is used, a switchgear used for power transmission / distribution and power receiving equipment will be described as an example, and the overall configuration will be described.

  FIG. 1 is a side cross-sectional view of a main part showing a configuration example of a switchgear. As shown in the figure, in a metal jacket 1 covering the whole, ground metal cases 2a to 2c hermetically sealed for housing a main circuit portion of a modular switchgear are arranged. The cases 2a to 2c are filled with an insulating gas such as SF6 gas, dry air, nitrogen gas or air to form an insulating gas atmosphere. A cable head 3 is attached to a side wall of a ground metal case 2a disposed in the lower stage of the metal jacket 1, and a vacuum circuit breaker 4 and a ground switch 5 are housed inside. The ground metal case 2b arranged on the upper stage houses a three-position disconnector 6 comprising a ground switch part 6a and a disconnector part 6b and a three-phase bus 7 connected thereto, and also in the ground metal case 2c. A three-phase bus 8 is housed. The metal cases 2a and 2b are connected by being partitioned by an insulating spacer 9. In addition, on the front side, operating mechanism portions 10a to 10c of opening / closing devices housed in the ground metal cases 2a and 2b are arranged.

  In the above, the sealed switchgear in which the main circuit device is housed in an insulating gas atmosphere is shown. However, an air switchgear in which the main circuit unit is disposed in the atmosphere may be used. The configuration is not limited to FIG.

  When the insulation structure of the electrical equipment of the present invention is applied to the switchgear as described above, the target is between the three-phase main circuit conductors (between phases) or between the main circuit conductors and the ground metal case ( (Between ground) or between contacts (between poles) of a switching device such as a grounding switch, the specific structure of which will be described later.

  FIG. 2 is a diagram showing the insulation structure of the electric device according to the first embodiment. For example, a high-voltage conductor and a grounding conductor facing the high-voltage conductor are modeled like a main circuit conductor and a ground metal case of the electric device. FIG. 2 is a partial cross-sectional view showing an insulating structure therebetween. The rod-shaped conductor 11 has a tip portion 11a formed in a hemispherical shape, and the tip portion 11a side faces the ground conductor 12 which is a counter conductor. Therefore, since a local high electric field is electrically formed at the tip of this conductor, the insulating layer 13 is provided so as to cover this portion. And the surface shape of the opposing surface 13a of the insulating layer 13 which faces the grounding conductor 12 is formed so that it may become a substantially plane. The dotted line in the figure shows a cross section of the equipotential surface.

Before explaining the operation of the insulating structure as described above, the mechanism by which the insulating layer covered with the high-voltage conductor leads to dielectric breakdown will be described.
When the high-voltage conductor is covered with an insulating layer, when the electric field of the maximum electric field generating portion on the surface of the insulating layer reaches a certain value, a preceding discharge called streamer occurs from the surface, and the high-voltage conductor exposed portion without the insulating layer is exposed. Start to make progress. When the streamer extends to the exposed portion, the streamer is a very thin conductive path, so that it appears that a very thin high-voltage conductor having a tip at the maximum electric field generating portion on the surface of the insulator appears. As a result, a very strong electric field is formed at the maximum electric field generating portion on the surface of the insulator, and discharge that propagates through the gas space is started by this electric field. When the discharge of the gas space portion is completed, the entire gap is short-circuited. With this mechanism, dielectric breakdown occurs in the gap in which the high-voltage conductor is covered with the insulating layer.

Therefore, in order to prevent dielectric breakdown in these gaps, it is important to prevent the generation of streamers as the beginning. For this purpose, it has been found that (1) reduction of the maximum electric field on the surface of the insulator and (2) reduction of the surface area of the portion where the high electric field is formed on the surface of the insulator are effective. (1) is a measure for preventing the generation of an electric field necessary for streamer generation. (2) relates to a so-called area effect in which the maximum electric field on the insulator surface necessary for streamer generation depends on the area of the insulator surface. For example, when the maximum electric field value is 100%, the relationship between the area where an electric field of 90% or more is generated (90% effective area, hereinafter abbreviated as effective area S90) and the breakdown electric field value on the surface of the insulating layer. Can be specifically expressed as: The electric field necessary for streamer generation is higher as the effective area S90 is smaller. Conversely, when the effective area S90 is larger, the electric field gradually decreases (finally converges to a saturated electric field).
In the following description, when an effective area is generally described, it is simply expressed as an effective area.

  FIG. 3 is a diagram showing the relationship between the above-described effective area S90 in dry air and the breakdown electric field value at which the insulating layer surface causes dielectric breakdown, and is obtained by experiments. In the figure, when a voltage between a high-voltage conductor and a ground conductor is applied, the maximum electric field value appearing on the surface of the insulating layer and its effective area S90 are plotted on this graph and plotted above the solid line of the graph. Insulation breakdown occurs and insulation is maintained when plotted below. As indicated by the white and black circles in the figure, even if the maximum electric field value is small, the effective area is large and above the solid line, dielectric breakdown occurs, but the effective area is small even if the maximum electric field value is large. If it falls below the solid line, dielectric breakdown does not occur. That is, it can be seen that the breakdown electric field value increases as the effective area S90 decreases, and dielectric breakdown is less likely to occur. Therefore, in order to improve the insulation performance, it is very effective to use an insulation structure that reduces the effective area.

Next, the operation of the insulating structure shown in FIG. 2 will be described.
As in the equipotential surface indicated by a broken line in the figure, in the conductor having the shape as shown in the figure, the surface of the insulating layer at the tip of the central axis of the conductor is the maximum electric field part. The effective area S90 described above exists in a circular shape centering on the point.
The outer shape of the insulating layer is, for example, a shape along the equipotential line as shown in FIG. 11A of Patent Document 1 described in the related art, and the opposite surface side of the insulating layer as in this embodiment. Compared with the case where the surface shape is substantially flat, in the present embodiment, as shown in FIG. 2, the equipotential portion is reduced and the effective area is reduced in the surface portion.

From the experimental results of comparing the effective area characteristics by conducting an electrolytic analysis of the insulation layer covering shape formed on the conductor surface with approximately the same thickness and the shape as shown in FIG. It was verified that the shape is more effective in improving the withstand voltage performance.
FIG. 4 is a diagram comparing the effective area characteristics between the conventional insulating structure along the equipotential line and the shape of the insulating structure of the present invention. The relationship of the insulator surface electric field (relative value) with respect to the effective area S90 is represented. As the curve in the figure shows, the structure of the present invention is in a lower position, which indicates that it has been improved to maintain insulation for higher voltage applications.

  In addition, although FIG. 2 demonstrated the case where a high voltage | pressure conductor and a ground conductor oppose, the same effect was confirmed also in the insulation structure in case the same-shaped conductors oppose, for example between the contacts of a switch.

Next, an example in which the above insulating structure is applied to a product will be described.
FIG. 5 is a partial cross-sectional view of a V portion indicated by a one-dot chain line in the switch gear of FIG. 1 described above, and is an electrode portion of the ground switch 5 that is a local high electric field. The electrode 14 on the high voltage side is provided with a through hole at the center of a rod-shaped conductor having a predetermined curvature at the tip, and an energizing contact 15 is provided on the inner peripheral surface thereof. The opposing low voltage side (grounding side) electrode 16 has substantially the same shape, and the movable rod electrode 17 can reciprocate in the axial direction through the central through hole. The surface portions of the opposing portions of the electrodes 14 and 16 are respectively covered with insulating layers 18 and 19, and the surface shapes of the insulating layers 18 and 19 on the side facing the counter electrodes are formed to be substantially flat. .
The ground layer electrode 16 is also provided with the insulating layer 19 because a high voltage may be applied to the electrode 16 to generate a local high electric field.

The operation of this electrode insulation structure will be described. The equipotential surface is indicated by a dotted line in the figure, and in the case of such a combination of the electrode and the shape of the insulating layer, the maximum electric field is generated in the vicinity of the outer peripheral edge of the facing surface of the insulating layer 18 and the effective area. S90 is a portion indicated by a thick line in the drawing. For comparison, an insulating structure in which similar electrodes 14 and 16 are covered with insulating layers 20 and 21 similar to the shape described in Prior Art Document 1 is shown in FIG. 6 as a reference example. In the case of FIG. 6, the insulating shape is such that the equipotential surface is along the surfaces of the insulating layers 20, 21, but as a result of experimental verification, the region of the effective area S90 is as shown by a bold line in the figure, It was confirmed that it was wider than in FIG.
That is, as in the present embodiment, if the surface shape of the insulating layers 18 and 19 facing the counter electrode is made to be a substantially flat surface, the effective area S90 becomes smaller than that of a conventional insulating layer, The breakdown electric field value increases accordingly.

  In addition, although FIG. 5 demonstrated as an electrode part of the reciprocating type earthing switch 5, electrodes, such as a disconnecting switch and a 3 position disconnecting switch, are the same shape in a switchgear, and can be applied similarly. Moreover, it is applicable also to the insulation structure between phases or between ground.

As described above, according to the embodiment of the present invention, the switching device and its main circuit conductor are housed in the ground metal case, and a local high electric field is formed in the insulating structure of the electrical device that insulates between the opposing conductors. An insulating layer is provided on the surface of the conductor to be formed, the surface shape of the insulating layer on the side facing the opposing conductor is formed in a substantially flat surface , and the thickness of the insulating layer is located at the shortest distance from the opposing conductor Since it is formed so as to become thicker as it is farther from , the effective area S90 on the surface of the insulating layer is reduced, and accordingly, the breakdown electric field value on the surface of the insulating layer is increased, so that the dielectric strength of the electric device can be improved. Accordingly, the electric device can be reduced in size.

In addition, an insulating layer is formed on the surface of the conductor that creates a local high electric field between the electrodes of the switchgear constituting the switchgear, between the phases of the main circuit conductor, or between the opposing conductors between the main circuit conductor and the ground metal case. The surface shape of the insulating layer facing the opposing conductor is formed in a substantially flat surface , and the thickness of the insulating layer is formed so that the distance from the opposing conductor increases away from the portion located at the shortest part. since the, smaller effective area S90 of the insulating layer surface, since the breakdown electric field value of the insulating layer surface is increased, it is possible to improve the dielectric strength, thus providing an excellent switchgear insulation performance.

Embodiment 2. FIG.
FIG. 7 is a partial cross-sectional view showing an insulating structure of an electric device according to the second embodiment. For example, a high-voltage conductor and a grounding conductor facing the high-voltage conductor are modeled like a main circuit conductor and a grounding metal case of the electric device. FIG. 3 is a partial cross-sectional view showing an insulating structure therebetween. The difference from the first embodiment is that the conductor is not covered with an insulating layer, but an insulating barrier is provided with a gap from the conductor.

  As shown in the figure, a ground conductor 23 is arranged opposite to a rod-shaped conductor 22 having a hemispherical tip, and the tip 22a of the conductor 22 is a portion that forms a local high electric field. Therefore, an insulating barrier 24 is provided on the side close to the conductor 22 between the conductor 22 and the ground conductor 23 which is the opposite conductor. The thickness of the insulating barrier 24 is formed so as to increase as the distance from the portion located at the shortest portion between the two conductors of the conductor 22 and the ground conductor 23 increases. That is, the portion of the insulation barrier 24 located on the conductor central axis is made the thinnest, and the thickness is increased as the distance from the central axis is increased. Furthermore, the surface of the insulating barrier 24 facing the ground conductor 23 side which is the opposing conductor is formed in a substantially flat surface.

  A process leading to dielectric breakdown in the case where an insulation barrier is inserted between the high-voltage conductor and the low-voltage conductor as described above and the insulation barrier is disposed so as to cover the surface of the high-voltage conductor will be described. First of all, partial discharge starts at a high electric field portion on the surface of the high-voltage conductor as the beginning of all-path breakdown between the gaps into which the insulation barrier is inserted. The space charge of the same polarity as the high-voltage conductor generated by this partial discharge spreads in the gap between the insulation barrier and the high-voltage conductor, and as a result, the high-voltage conductor appears to be large and is almost in contact with the inner surface of the insulation barrier. Become. In this case, the subsequent all-path destruction process behaves in the same manner as in the case of the insulating layer of the first embodiment. Therefore, as described in the first embodiment, in order to improve the insulation performance, it is preferable to use an insulation structure with a small effective area.

In FIG. 7, the equipotential surface is as indicated by a dotted line in the figure. As shown in the figure, the outer corner portion of the insulating barrier 24 on the side facing the ground conductor 23 is a portion where the maximum electric field is generated, but the portion indicated by the bold line generates an electric field of 90% or more of the maximum electric field around it. This is a region having an effective area S90. Compared with the insulating barrier structure having a similar shape to that of FIG. 11B described in Patent Document 2 of the prior art (abbreviated as the conventional structure), in the conventional structure, a considerably wide area of the outer tip of the insulating barrier is effective. Although the area is S90, it was verified that the effective area S90 in FIG. 7 is smaller than that.
It should be noted that the portion where the maximum electric field is generated does not necessarily occur at the outer corner as shown in the figure, but depends on the shape of the tip of the conductor 22, the size of the insulating barrier 24, or a conductor existing nearby. Will change.

In the above description, the surface of the insulating barrier 24 that faces the ground conductor 23 is a flat surface, but the facing surface is not necessarily a flat surface. It was confirmed that even if the peripheral part was formed thicker than the central part, there was an effect.
However, since the shape of the tip end portion of the conductor 22 is usually rounded with a certain curvature, it is necessary to make the insulating barrier 24 thicker at the periphery and to make the opposing surface flat. As a result, the distance between the insulation barrier and the ground conductor can be increased.

Next, a case where the above insulating structure is applied to a specific product will be described.
FIG. 8 is a partial cross-sectional view of a V portion indicated by a one-dot chain line in the switch gear of FIG. 1 described in the first embodiment, and is an electrode portion of the ground switch 5 serving as a local high electric field. The high voltage side electrode 25 is provided with a through hole at the center of a rod-shaped conductor having a predetermined curvature at the tip, and an energizing contact (not shown) on the inner peripheral surface. The opposing low voltage side (grounding side) electrode 26 has substantially the same shape, and a movable rod electrode (not shown) can reciprocate in the axial direction in the central through hole. Insulation barriers 27 and 28 are provided in the vicinity of the electrodes 25 and 26 on the opposite side of the electrodes 25 and 26, respectively, and the thickness of the insulation barriers 27 and 28 is set to the shortest part of the electrodes 25 and 26. The periphery is thicker than the position. Moreover, the side facing each counter electrode of each insulation barrier 27 and 28 is formed so that the surface may become a substantially plane.

  The operation of the insulating structure of the switchgear will be described. As shown by the equipotential surface in the figure, the maximum electric field is generated in the vicinity of the outer peripheral edge of the opposing surface of the insulating barriers 27 and 28, and the effective area S90 is the part indicated by the thick line in the figure. It has been experimentally verified that the area of the effective area S90 has a smaller area than, for example, an insulating structure similar to the conventional structure.

  Next, another application example will be described. FIG. 9 is an example applied to another part of the switchgear and is a view seen from arrows IX-IX in FIG. That is, it is sectional drawing of the electrode part of the earthing switch part 6a of the reciprocating type 3 position disconnector 6, and shows two phases of A phase and B phase among three phases. The insulating barriers 29a and 29b have a U-shaped cross section and are disposed so as to surround the periphery of the electrode portions 30a and 30b, and insulate the phases of the electrode portions and the electrode portion and the ground metal case 2b. To do. The insulating barriers 29a and 29b are formed such that the portions located between the phases of the electrode portions 30a and 30b and the shortest portion between the electrode 30a and the ground metal case 2b are the thinnest and become thicker as they are separated from each other. . Furthermore, the insulating barrier surface facing the opposing conductor is formed in a substantially flat surface. That is, in the case of the A-phase insulation barrier 29a, the surface facing the B phase and the surface facing the ground metal case 2b.

  With such an insulating barrier, the area of the effective area S90 can be reduced and the dielectric strength can be improved, as in the case of FIG. 7 or FIG.

  The surface of the insulating barrier facing the opposing conductor does not necessarily have to be a flat surface. FIG. 10 is a view showing another example of the insulation barrier provided in the same portion as FIG. As shown in the insulating barriers 31a and 31b in the figure, the effect of narrowing the area of the effective area can be expected if the periphery is thicker than the portion located at the shortest portion between the two opposing conductors. .

  The insulating structure described above is not limited to V part or IX in FIG. 1, but can be similarly applied to other parts of disconnector, grounding switch, or three-position disconnector.

As described above, according to the embodiment of the present invention, in the insulating structure that insulates between the opposing conductors of the electrical device in which the switchgear and its main circuit conductor are housed in the ground metal case, the conductor is locally localized. An insulating barrier is disposed in the vicinity of the conductor side that forms a local high electric field between the two conductors of the conductor that forms a high electric field and the opposing conductor, and the surface shape of the insulating barrier on the side facing the opposing conductor is made substantially planar. Since the insulating barrier is formed so that the thickness of the insulating barrier increases as the distance from the portion located at the shortest portion between the two conductors increases, the effective area S90 of the insulating barrier surface decreases, and the breakdown electric field of the insulating barrier surface Since the value increases, the dielectric strength can be improved. Accordingly, the electric device can be reduced in size .

In addition, two conductors, ie, a conductor having a local high electric field between the electrodes of the switchgear constituting the switchgear, between the phases of the main circuit conductor, or between the opposing conductors between the main circuit conductor and the ground metal case, and the opposing conductor An insulating barrier is disposed in the vicinity of the conductor side that forms a local high electric field between them, the surface shape of the insulating barrier facing the opposing conductor is formed in a substantially flat surface, and the thickness of the insulating barrier is set to two conductors The effective area S90 of the insulating barrier surface is reduced and the breakdown electric field value of the insulating barrier surface is increased, so that the effective area S90 of the insulating barrier surface is increased. It is possible to improve the dielectric strength between the electrode portion and the ground metal case, and to provide a switchgear with improved withstand voltage performance .

It is a block diagram of the switchgear which applies the insulation structure of the electric equipment by Embodiment 1 of this invention. It is sectional drawing which shows the insulation structure of the electric equipment by Embodiment 1 of this invention. It is a figure showing the relationship between the breakdown electric field in an insulating surface, and an effective area. It is the figure which compared the effective area characteristic of the insulation structure of this invention, and the conventional structure. It is a fragmentary sectional view which shows the electrode part of the earthing switch of the switchgear by Embodiment 1 of this invention. It is a figure which shows the reference example for a comparison with FIG. It is sectional drawing which shows the insulation structure of the electric equipment by Embodiment 2 of this invention. It is a fragmentary sectional view which shows the electrode part of the earthing switch of the switchgear by Embodiment 2 of this invention. It is a fragmentary sectional view which shows the insulation barrier of the earthing switch part of the switchgear by Embodiment 2 of this invention. It is a fragmentary sectional view which shows the other example of the insulation barrier of the switchgear by Embodiment 2 of this invention. It is a fragmentary sectional view of the electrode part which shows the insulation structure of the conventional electric equipment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal sheath 2a-2c Ground metal case 3 Cable head 4 Vacuum circuit breaker 5 Ground switch 6 Three position disconnector 6a Ground switch part 6b Disconnector part 7, 8 Bus 9 Insulating spacer 10a-10c Operation mechanism part 11, 22 Conductor 11a, 22a Tip portion 12, 23 Ground conductor 13 Insulating layer 13a Opposing surface 14, 16, 25, 26 Electrode 15 Current contact 17 Movable rod electrode 18, 19, 20, 21 Insulating layer 24, 27, 28, 29a , 29b, 31a, 31b Insulation barrier 30a, 30b Electrode portion.

Claims (2)

In the insulation structure of electrical equipment in which the switchgear and its main circuit conductor are housed in a grounded metal case and insulate between opposing conductors,
An insulating barrier is disposed in the vicinity of the conductor forming the local high electric field between the two conductors of the conductor that forms a local high electric field and the opposing conductor, and the conductor facing the opposing conductor The surface shape of the insulating barrier is formed in a substantially flat surface, and the thickness of the insulating barrier is continuous from the portion located at the shortest portion between the two conductors as it moves outward in the direction parallel to the substantially flat portion of the insulating barrier. insulation structure of an electric device, characterized in that it is formed to be thicker and. In the switchgear in which the switchgear and its main circuit conductor are housed in a grounded metal case,
Between the electrodes of the switchgear, between the phases of the main circuit conductor, or between the opposing conductors between the main circuit conductor and the ground metal case, between the two conductors of the conductor and the opposing conductor that form a local high electric field An insulating barrier is disposed in the vicinity of the conductor side forming the local high electric field, the surface shape of the insulating barrier on the side facing the opposing conductor is formed in a substantially plane, and the thickness of the insulating barrier is: A switchgear, wherein the switchgear is formed so as to continuously increase from the portion located at the shortest portion between the two conductors toward the outer side in the direction parallel to the substantially flat portion of the insulating barrier .

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