JP4949919B2 - Gas insulated electrical equipment - Google Patents

Description

  The present invention relates to a gas-insulated electrical apparatus in which a high-voltage conductor is housed in a metal container, and the metal container is filled with an insulating gas to insulate the high-voltage conductor from the metal container.

The breakdown voltage performance of gas-insulated electrical equipment includes dielectric breakdown from a high-voltage conductor that is a high electric field portion. In conventional gas-insulated electrical equipment, a technique is known in which an insulation coating is applied on a high-voltage conductor with a coating in order to suppress dielectric breakdown from the high-voltage conductor and increase the breakdown voltage. This is a method of suppressing the electron emission from the metal surface of the high-voltage conductor, which becomes the initial electrons of discharge, with an insulating coating, thereby improving the breakdown voltage.
Further, for example, in a gas-insulated bus in which a bus that is a high-voltage conductor is disposed in a metal container filled with an insulating gas and the bus is insulated and supported with respect to the metal container by a support insulator, the outer surface of the bus and A technique is disclosed in which a fluorine resin coating is provided on each of the inner surfaces of a metal container to suppress the behavior of metal foreign matter existing in the metal container and improve the pressure resistance (see, for example, Patent Document 1).

JP-A-5-30626 (second page, FIG. 1)

As described above, the insulation coating with a coating on the high-voltage conductor has the effect of suppressing electron emission, but when the insulation coating is a thin film, it completely suppresses the electrode area effect that causes the breakdown voltage to decrease. It is difficult to make it.
Further, in the bus insulation employing the composite insulation system as shown in Patent Document 1, it is possible to suppress the electron emission and the electrode area effect, but the insulation coating covers the metal surface on the entire surface of the bus conductor and the inner surface of the metal container. Therefore, when the dielectric breakdown occurs even once, the insulation coating breaks through, and thereafter, the insulation coating loses its function as an insulator and the dielectric strength is significantly reduced. Since the insulating gas itself has an insulation recovery capability, for example, in the case of an insulating configuration of only an insulating gas with a metal electrode not provided with an insulating coating, the same breakdown voltage can be maintained against multiple breakdowns. In such an insulating configuration, there is a problem that the same breakdown voltage cannot be maintained once dielectric breakdown occurs.

  The present invention has been made to solve the above-described problems, and an object thereof is to obtain a gas-insulated electric apparatus that can maintain the same withstand voltage even after dielectric breakdown occurs.

A gas-insulated electrical apparatus according to the present invention includes a metal container filled with an insulating gas, a high-voltage conductor that is contained in the metal container and applied with a predetermined voltage, and the high-voltage conductor is insulated and supported by the metal container. In a gas-insulated electrical apparatus comprising an insulating support member that performs electric field relaxation shielding that relaxes an electric field at a connection portion between the high-voltage conductor and the insulating support member, the metal surface of the high-voltage conductor and electric field relaxation shield is covered with a dielectric. A metal exposed portion is formed by exposing the metal surface to a part of the dielectric coating film applied to the high voltage conductor, and the metal exposed portion is in the middle of the longitudinal direction of the high voltage conductor. At least one or more places are formed .

According to the gas-insulated electrical apparatus of the present invention, the dielectric coating film is applied to the metal surfaces of the high-voltage conductor and the electric field relaxation shield, and at least one of the dielectric coating films in the middle of the longitudinal direction of the high-voltage conductor. Since the metal exposed part where the metal surface of the high voltage conductor is exposed is formed above the location , the high voltage conductor and the electric field relaxation shield are improved in withstand voltage by the dielectric coating film, and from the dielectric coating film at the time of dielectric breakdown. Even if the discharge occurs, the discharge progresses toward the exposed metal portion and becomes a creeping discharge on the surface of the dielectric coating film, thereby preventing the dielectric coating film from penetrating. Therefore, the second and subsequent dielectric breakdown voltages can maintain the initial state.

Embodiment 1 FIG.
1 is a cross-sectional view showing a gas-insulated electrical apparatus according to Embodiment 1 of the present invention.
In the gas-insulated electric apparatus, a central conductor 2 that is a high-voltage conductor to which a high voltage is applied is accommodated in a cylindrical metal container 1 that is a pressure vessel, and the metal container 1 and the central conductor 2 are insulated from each other. For this purpose, an insulating gas 3 such as SF ₆ gas is filled. The center conductor 2 is supported and fixed at the coaxial center position of the metal container 1 by an insulating spacer 4 which is an insulating support member made of a solid insulator. Furthermore, an electric field relaxation shield 5 that relaxes the electric field at the connection portion is provided at the connection portion between the insulating spacer 4 and the central conductor 2 so as to cover the connection portion.

  When the metal container 1 and the center conductor 2 have a coaxial cylindrical structure, the center conductor 2 is a high electric field portion. Therefore, a dielectric coating film 6 is applied to the surface of the central conductor 2 and the surface of the electric field relaxation shield 5 that is a higher electric field portion in order to prevent a decrease in breakdown voltage due to the electrode area effect depending on the electrode area. . As a feature of the present invention, a metal exposed portion 7 in which the metal surface of the center conductor 2 is exposed is formed on a part of the dielectric coating film 6 applied to the center conductor 2.

The material of the dielectric coating film 6 is preferably composed of an insulator such as epoxy resin, acrylic resin, fluororesin, rubber resin, polyethylene, and polypropylene.
The thickness of the dielectric coating film 6 is set to a certain thickness or more so as not to break through even when an electric field corresponding to an applied voltage is applied by discharge at the time of dielectric breakdown. The actual thickness varies greatly depending on the material used and the place to be coated, but is, for example, on the order of 1 mm or more.
The dielectric coating film 6 can be formed by a mold casting method, a powder coating method such as electrostatic coating or fluid dipping method, a method of coating a liquid resin such as paint, a method of winding an insulating sheet, shrinkage, etc. The method etc. which cover a tube etc. are mentioned.

Next, the operation of the dielectric coating film 6 will be described.
In the case of the coaxial cylindrical structure, an electric field gradient exists in the radial direction, but the electric field is constant in the circumferential direction and the longitudinal direction. Therefore, the surface area of the central conductor 2 is almost the same electric field. Normally, an insulator has a discharge start or dielectric breakdown determined by an electric field value. However, in SF ₆ gas, the breakdown electric field value depends on the area due to the electrode area effect caused by micro protrusions of the electrode. In the case of a gas-insulated electric device for high voltage, the surface area of the central conductor 2 is 100,000 mm ² or more, so that the breakdown electric field value is greatly reduced by the electrode area effect as compared with the case of a small electrode area.
Therefore, by insulatingly coating with the dielectric coating film 6, micro protrusions on the conductor surface can be masked and the breakdown voltage can be improved.

  The dielectric coating film 6 is generally formed on the entire surface of the central conductor 2 and the electric field relaxation shield 5 that have a high electric field. However, in the invention of the present embodiment, as described above, a part of the dielectric coating film 6 is formed. The metal exposed portion 7 where the dielectric coating film 6 is not formed is provided, and this operation will be described below.

First, the process leading to dielectric breakdown will be described based on the explanatory diagram of FIG.
In the portion of the coaxial cylindrical structure of the gas-insulated electrical apparatus, the radial electric field is higher on the central conductor 2 side and lower on the wall surface side of the metal container 1. Therefore, the discharge starts from the center conductor 2 side. The main insulation of the center conductor 2 is a composite insulation of the insulating gas 3 and the dielectric coating film 6. Since the breakdown voltage of the insulating gas 3 is lower than that of the solid insulator in the solid / gas composite insulating system, discharge generally starts from the maximum electric field portion of the gas space. In this system, it becomes the surface of the dielectric coating film 6, and the probability of starting discharge from this surface is the highest. Since the discharge is completed by bridging between the high voltage electrode and the low voltage electrode, the surface of the dielectric coating film 6 of the center conductor 2 or the electric field relaxation shield as in the discharge path 8a or the discharge path 8b in FIG. The electric discharge started from the surface of 5 progresses toward the inner wall surface of the metal container 1 on the low pressure side and the central conductor 2 on the high voltage side.

  At this time, if the entire surface of the central conductor 2 on the high voltage side is covered with the dielectric coating film 6, the dielectric coating film 6 is penetrated to reach the metal portion and complete the discharge. There must be. When the through breakage occurs, the fracture mark of the dielectric coating film 6 is a large hole where the effect of the coating film is lost or a breakdown path with a low electrical resistance remains even if the hole does not become so much. Becomes a weak point in insulation, and the dielectric strength is greatly reduced as compared to when it is not broken.

However, in the invention of the present embodiment, since the metal exposed portion 7 in which the metal surface is partially exposed is formed in the central conductor 2 on the high voltage side, the discharge penetrates the dielectric coating film 6. Rather than this, it progresses toward the portion of the exposed metal portion 7, reaches the exposed portion across the surface of the dielectric coating film 6, and leads to dielectric breakdown.
Therefore, it is possible to prevent the dielectric coating film 6 from being broken due to dielectric breakdown and greatly reducing its insulating function.

In the configuration as described above, by exposing a part of the metal surface on the high voltage side into the gas space, the exposed part may become a discharge starting point. Accordingly, the appropriate size of the exposed portion will be described next.
FIG. 3 shows (gap width / dielectric coating film thickness) when a gap without a coating film is provided in the radial direction of the central conductor 2 in order to form the metal exposed portion 7 in the dielectric coating film 6. It is a figure which shows the relationship between the electric field strength of a metal surface. As shown in the figure, when the value of (gap width / dielectric coating thickness) becomes smaller than about 10, the electric field strength suddenly decreases. As can be seen, the electric field on the metal surface can be lowered by narrowing the exposed portion of the metal surface to a certain distance or less. Accordingly, by selecting a gap distance that makes the electric field of the metal surface less than or equal to the breakdown electric field while considering the film thickness of the dielectric coating film 6 to be used, the dielectric coating film can be obtained without causing a discharge start point. Thus, the high breakdown voltage can be maintained.

  As described above, according to the invention of the present embodiment, the high voltage conductor is accommodated in the metal container filled with the insulating gas and supported by the insulating support member, and is connected to the connection portion between the high voltage conductor and the insulating support member. In gas-insulated electrical equipment equipped with an electric field relaxation shield, a dielectric coating is applied to the metal surface of the high-voltage conductor and electric field relaxation shield, and the metal surface is exposed to a portion of the dielectric coating film applied to the high-voltage conductor. Since the exposed metal exposed portion is formed, the dielectric coating film improves the breakdown voltage, and the discharge at the time of dielectric breakdown bridges the insulating gas portion so that a high voltage is applied only to the dielectric coating film. Even so, since the discharge proceeds toward the exposed metal portion, it becomes a creeping discharge on the surface of the dielectric coating film, preventing penetration breakdown, and maintaining the initial breakdown voltage for the second and subsequent times.

Embodiment 2. FIG.
FIG. 4 is a cross-sectional view of the central conductor portion of the gas-insulated electrical apparatus according to the second embodiment. This is a portion corresponding to the central conductor portion of FIG. 1 of the first embodiment and is the same as FIG. Moreover, although the equivalent part is shown with the same code | symbol, especially the dielectric material coating film given to the surface of the center conductor 2 is made into the code | symbol 6a among dielectric material coating films, and the center conductor 2 is shown among metal exposure parts. The metal exposed portion formed in the longitudinal direction is distinguished as 7a. The invention of this embodiment relates to a portion of a metal exposed portion.

As shown in the figure, the dielectric coating film 6a is applied in close contact with the cylindrical center conductor 2, but in the longitudinal direction (axial direction of the center conductor 2), a certain interval (equal interval). The metal exposed portion 7a in which the metal surface of the conductor is exposed in the space of the insulating gas 3 is provided. The exposed metal portion 7a is provided in a circle in the circumferential direction of the central conductor 2, and the width thereof is a gap distance that makes the electric field on the metal surface equal to or less than the breakdown electric field, as described in the first embodiment.
Further, one or more metal exposed portions 7 a are provided in the longitudinal direction of the central conductor 2. For example, if the center conductor 2 is supported at both ends by insulating spacers, at least one metal exposed portion 7a is provided between the insulating spacers.

  As described above, since the electric field of the surface of the central conductor 2 in the longitudinal direction is lower than that of the electric field relaxation shield 5, the possibility of dielectric breakdown is low, but the possibility of occurrence is not zero. When the discharge occurs, the creeping discharge crawls through the dielectric coating film 6a in the longitudinal direction of the center conductor 2. Since the length in the longitudinal direction is as long as several meters, it is difficult for creeping discharge to proceed, and there is a possibility that the dielectric coating film 6 may first break through. Therefore, as in the configuration of the present invention, by providing the metal exposed portions 7a at regular intervals in the longitudinal direction, the discharge progresses toward that portion and reaches the metal exposed portions 7a. It is possible to prevent penetration destruction of the covering film 6a.

  As described above, according to the invention of the present embodiment, at least one or more metal exposed portions formed in a part of the dielectric coating film applied to the high voltage conductor are formed in the longitudinal direction of the high voltage conductor. Therefore, when a discharge occurs in the high-voltage conductor, a discharge path is formed in the exposed metal portion provided in the longitudinal direction, so that the dielectric coating film can be prevented from being broken through, and insulation can be performed multiple times. It is possible to prevent a decrease in dielectric breakdown strength even after breakdown.

Embodiment 3 FIG.
FIG. 5 is a cross-sectional view showing an electric field relaxation shield part of a gas-insulated electrical apparatus according to Embodiment 3. The gas-insulated electric apparatus is the same as that in FIG. 1 of the first embodiment, and only the electric field relaxation shield portion is shown enlarged. Parts equivalent to those in FIG. However, among the dielectric coating films, the dielectric coating film applied to the surface of the central conductor 2 is distinguished by reference numeral 6a, and the dielectric coating film applied to the surface of the electric field relaxation shield 5 is distinguished by reference numeral 6b. .
The invention of the present embodiment relates to a portion of the exposed metal portion, and is an example different from the second embodiment.

  As shown in the figure, the electric field relaxation shield 5 is provided with a dielectric coating film 6b over the entire surface thereof. On the other hand, the central conductor 2 side is a connection portion with the insulating spacer 4 that is an insulating support member, and the end portion of the central conductor 2 that enters the inside of the electric field relaxation shield 5 serves as a metal exposed portion 7b, and the other portion, that is, the electric field. A dielectric coating film 6 a is applied to an outer portion that is not hidden by the relaxation shield 5. However, as described in the second embodiment, the outer dielectric coating film 6a may be provided with the metal exposed portions 7a at a certain interval.

  Since the electric field relaxation shield 5 has a structure in which the electric field is higher than that of the surface portion in the longitudinal direction of the center conductor 2, the electric field relaxation shield 5 is more likely to break down than the center conductor 2. Therefore, the entire outer surface portion of the electric field relaxation shield 5 is covered with the dielectric coating film 6b so as not to be exposed to the gas space, to maintain a high breakdown voltage due to the effect of the dielectric coating film 6, and to be insulated. When the breakdown occurs, the surface discharge progresses to the inside of the electric field relaxation shield 5 and reaches the inner metal exposed portion 7b as in the discharge path 8b in FIG. It is possible to prevent the dielectric coating film 6b of the electric field relaxation shield 5 from being broken through, and it is possible to prevent a decrease in dielectric breakdown strength even after a plurality of dielectric breakdowns.

  The insulating support member may be, for example, a conical insulating spacer, or may be a post-type spacer that is supported from the metal container 1 by a column system.

  As described above, according to the invention of the present embodiment, the end portion of the high voltage conductor that has entered the inside of the electric field relaxation shield is the metal exposed portion at the connection portion between the high voltage conductor and the insulating support member. By covering the outer surface of the electric field relaxation shield part, which becomes a higher electric field part than the center conductor part, with a dielectric coating film and eliminating the metal surface, the withstand voltage is improved. The creeping discharge path can be formed to prevent the dielectric coating film from penetrating.

  In the first to third embodiments, the gas-insulated electric device has been described as being configured with the central conductor supported by the insulating spacer in the sealed container, but is not limited thereto, for example, It can be applied to each part of a gas insulated switchgear composed of a circuit breaker, a disconnector, a ground switch, a lightning arrester, a main bus, and the like.

It is sectional drawing which shows the gas insulated electrical apparatus by Embodiment 1 of this invention. It is explanatory drawing explaining the dielectric breakdown process of the gas insulated electrical apparatus by Embodiment 1 of this invention. It is a figure which shows the relationship between the film thickness of the dielectric coating film by Embodiment 1 of this invention, the clearance gap width of a metal exposure part, and electric field strength. It is sectional drawing which shows the center conductor part of the gas insulated electrical equipment by Embodiment 2 of this invention. It is sectional drawing which shows the electric field relaxation shield part of the gas insulated electrical equipment by Embodiment 3 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal container 2 Center conductor 3 Insulating gas 4 Insulating spacer 5 Electric field relaxation shield 6, 6a, 6b Dielectric coating film 7, 7a, 7b Metal exposure part 8a, 8b Discharge path.

Claims (3)

A metal container filled with an insulating gas; a high-voltage conductor that is accommodated in the metal container and to which a predetermined voltage is applied; an insulating support member that insulates and supports the high-voltage conductor on the metal container; and the high voltage In a gas-insulated electrical apparatus including an electric field relaxation shield that relaxes an electric field at a connection portion between a conductor and the insulating support member,
A metal exposed portion in which a dielectric coating film is applied to a metal surface of the high voltage conductor and the electric field relaxation shield, and the metal surface is exposed in a part of the dielectric coating film applied to the high voltage conductor. Is formed ,
At least one or more metal exposed portions are formed in the middle of the high-voltage conductor in the longitudinal direction . 2. The gas insulated electric device according to claim 1, wherein the exposed metal portions are provided at a certain interval in the longitudinal direction . In the gas insulated electric apparatus according to claim 1 or claim 2, at the junction of the front Symbol high voltage conductor and the insulating support member, an end portion of said high voltage conductor that enters the inside of the electric field relaxation shield, A gas-insulated electrical apparatus, wherein a metal exposed portion different from the metal exposed portion is formed.

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