JPH0928010A - Gas insulated switchgear, gas insulated transmission line, and insulating spacer therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the creeping dielectric strength of an insulating spacer by tightly sticking a surface member having a low dielectric strength to a central member composed of a material having a high dielectric constant with a coupling agent. SOLUTION: Buried electrodes 5a and 5b and a cylindrical insulating layer 3a which is a central member are formed by injection molding. In addition, an insulating layer 3b which is a surface member 3b having a low dielectric constant is formed around the cylindrical insulating layer 3a composed of a high dielectric constant. At the time of forming the insulating layer 3b, the surface member 3b is injection-molded after a silane coupling agent is applied to the outer peripheral surface of the central member 3a. Therefore, even when conductive foreign matters exist in a gas insulated switchgear and the foreign matters adhere to an insulating spacer, the foreign matters certainly adhere to the insulating layer 3b, because the surface member 3b covers the central member 3a. As a result, the dielectric strength of the insulating spacer is improved as compared with a single-layer spacer having a high dielectric constant.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to sulfur hexafluoride (SF ₆ ).
The present invention relates to a gas insulated switchgear (GIS) and a pipeline air transmission line (GIL) that use an insulating gas such as a gas as an insulating medium, and particularly to an insulating spacer having a high insulating performance for insulating and supporting a high-voltage conductor.

[0002]

2. Description of the Related Art Gas-insulated switchgear using SF ₆ gas as a main insulating medium is widely used in power plants, substations, etc. because of its excellent insulation reliability and miniaturization of the device. . However, as the demand for electric power has increased in recent years, the transmission system is required to have a large capacity up to 550 kV or UHV. The gas-insulated switchgear used in these power substations is required to have higher reliability and economical efficiency, and is strongly desired to be compact.

Since the conventional gas insulated switchgear uses an insulating gas such as SF ₆ gas, the device can be made compact, but there is a conductive foreign substance of about several mm in the metal container. There is a risk of dielectric breakdown just by being there. For example, when there is a conductive foreign substance in the metal container, the conductive foreign substance is charged depending on the shape and the like, and reciprocates between the high voltage conductor in the center and the surrounding metal container.

If an overvoltage such as a lightning impulse or a disconnector surge is applied to the gas switchgear when the conductive foreign matter adheres to the surface of the insulating spacer, the dielectric breakdown of the insulating spacer is very likely to occur. The main cause of the ground fault in the gas-insulated switchgear is the surface dielectric breakdown of the insulating spacer due to the conductive foreign matter as described above, and the management of the conductive foreign matter is an important issue. However, it is very difficult to eliminate the conductive foreign matter in the manufacturing of the device, and it is necessary to design the device so that the insulating design takes into consideration the mixing of the conductive foreign matter.

Therefore, conventionally, in order to prevent a surface dielectric breakdown, as described in JP-A-6-153342, a material (fluorine resin) having a lower dielectric constant than the material of the insulating spacer is formed on the surface of the insulating spacer. Taking measures to coat.

[0006]

In the prior art described above, the surface of the insulating spacer is coated with a material having a low dielectric constant so that when the conductive foreign matter adheres to the surface of the insulating spacer, the electric field in the vicinity of the conductive foreign matter becomes large. This is to ease concentration. This idea is useful in preventing creeping dielectric breakdown, but there is a problem that must be solved before actually applied to the gas insulated switchgear. Set the surface of the insulating spacer to 10
Even if it is covered with a thin film having a low dielectric constant of about 0 μm, the effect of preventing electric field concentration is too small. In order to prevent creeping dielectric breakdown, the surface of the insulating spacer must be covered with a low dielectric constant material having a thickness of at least several mm or more with respect to the thickness of the insulating spacer of several cm. Therefore,
An insulating spacer in which an insulating spacer having a thickness of several cm and a low dielectric constant material having a thickness of at least several mm are laminated is prepared. However, the problem here is that the conductive foreign matter adhered to the surface of the low dielectric constant material Although it is possible to prevent electric field concentration on the
There is a possibility that dielectric breakdown may occur through the joint between the insulating spacer and the low dielectric constant material.

An object of the present invention is to provide a compact gas-insulated switchgear or the like having sufficient insulation performance and its insulating spacer.

[0008]

The above object is to provide an insulating spacer for insulating and supporting between a high voltage conductor of a gas insulated switchgear or a pipeline air transmission line and a hermetically sealed container for hermetically holding the high voltage conductor. A center member made of a high dielectric constant material, a surface member made of a low dielectric constant material disposed on the surface of the center member, and a coupling agent for closely bonding the center member and the surface member. It is achieved by doing.

Preferably, the central member has a dielectric constant of 5 or more, and the surface member has a dielectric constant of 3.5 to 4.5.

More preferably, the thickness of the surface member is at least 3 mm or more.

The above object is also achieved by making the density of the inorganic filler to be filled in the insulating spacer smaller than that of the central portion of the surface portion and integrally forming the same.

Preferably, the density of the inorganic filler is such that the central part has a dielectric constant of 5 or more and the surface part has a dielectric constant of 3.5.
It should be ~ 4.5.

[0013]

[Function] The thick low-dielectric constant material placed on the surface reduces the capacitance of the creeping portion, which increases the corona starting voltage due to the electric field concentration when conductive foreign matter adheres, and creeping insulation The yield strength is improved. In addition, the weak point of low mechanical strength of low dielectric constant material is that by using a high dielectric constant material with sufficient strength to support the load in the center,
The mechanical strength is improved. Furthermore, thick low-dielectric-constant material may cause dielectric breakdown at the interface with the high-dielectric-constant material, but since the two are tightly bonded using a coupling agent, this dielectric breakdown Is prevented.

[0014]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 4 is a diagram showing the principle structure of the busbar portion of the gas insulated switchgear. An example applied to a gas-insulated switchgear will be described. A pipeline air transmission line (apparatus)
The same applies to the above, so description of the pipeline air transmission line will be omitted. In FIG. 4, reference numeral 1 is a metal-enclosed container having a ground potential, which is mainly filled with an insulating gas such as SF ₆ gas, and 2 is a high-voltage conductor. Reference numeral 4 denotes a cone-type insulating spacer arranged at predetermined intervals, and the cone-type insulating spacer 4 insulates and supports the high-voltage conductor 2 in the metal closed container 1. The high voltage conductor 2 between the cone type insulating spacers 4 is insulated and supported by the epoxy cast resin insulating spacers 3.

FIG. 1 is an enlarged view of the gas-insulated switchgear of FIG. 4 as viewed from the axial direction (the insulating spacer 3 is a sectional view), and FIG. 2 is a sectional view of the insulating spacer 3. is there. In FIG. 1 and FIG. 2, the insulating layer 3a, which is a cylindrical central member cast with the embedded electrodes 5a and 5b.
Is formed of an epoxy resin mixed with an inorganic filler. The central member 3a is made of, for example, an epoxy resin filled with alumina (Al ₂ O ₃ ) in order to have the strength required to support the load applied to the insulating spacer 3.
The dielectric constant is 5 or more.

This embodiment is an example in which the diameter of the central member (insulating layer) 3a is substantially equal to the diameter of the embedded electrodes 5a and 5b, and the insulating layer 3a supports the load applied to the spacer 3. Around the cylindrical insulating layer 3a, an epoxy resin containing a small amount of the inorganic filler is cast to form an insulating layer 3b which is a surface member having a dielectric constant of about 3.5 to 4.5. . Only the surface member 3b has a spheroidal shape, and the central member 3a and the embedded electrode 5 are provided on the major axis portion.
It has a structure in which a and 5b are fitted together. The specific dimensions of the insulating spacer shown in FIG. 1 are as follows: the maximum outer peripheral portion (the maximum outer peripheral portion of the surface member 3b) has a diameter of 8 cm, and the central member 3a.
Has a diameter of 4 cm.

After forming the central member 3a, the surface member 3
b is cast, but at this time, if the two (3a, 3b) are not in close contact with each other, dielectric breakdown may occur at the interface between the two. Therefore, in this embodiment, both (3a, 3
After forming the central member 3a so that a silane coupling agent such as amino-functional silane or epoxy-functional silane is filled between b), the silane coupling agent is attached to the outer periphery of the central member 3a, and then Then, the surface member 3b is cast.

In the gas-insulated switchgear for insulating and supporting the high-voltage conductor 2 in which the insulating spacer 3 having the above-mentioned structure is provided, the conductive foreign matter exists in the apparatus, and the conductive foreign matter moves in the operating electric field. Even if this conductive foreign substance adheres to the insulating spacer 3, since the surface member 3b covers the entire outer periphery of the central member 3a, the conductive foreign substance always adheres to the insulating layer 3b having a low dielectric constant.

Here, if a surge voltage is applied to the gas-insulated switchgear, electric field concentration occurs near the conductive foreign matter attached to the insulating spacer, and a reader channel is formed. The conductivity of the reader channel is very large, and the potential gradient in the length direction is only 0.1-0.2 (kV / mm),
It is orders of magnitude smaller than the electric potential gradient of Streamer Corona 3 to 4 x P (kV / mm) (P: Gas pressure [bar]). In order to achieve such a high conductivity, the temperature of the reader channel needs to be about 2000K.

When the electric field at the tip of the leader channel exceeds Ecr (corona starting voltage), discharge is started and a streamer corona with strong light emission is formed. And the electric field is relaxed by the space charge created by the streamer corona, and the discharge stops,
The generated electrons collide with molecules and heat the reader channel. The heating energy of about 2000 K for forming the leader channel usually requires an implantation energy Δh of 10 ⁷ J / kg. The voltage Vcr required for this is given by the following equation 1 depending on the condition of energy balance.

[0021]

[Equation 1]

At this time, A is a scaling coefficient, P is a gas pressure, C is a capacitance between the reader and the counter electrode, and xL is a leader length, and the injection energy is transmitted through the capacitance between the reader and the counter electrode. Is supplied as a discharge, and the discharge progresses. for that reason,
When the relative permittivity of the spacer between the reader and the electrode becomes small, the electrostatic capacitance C becomes small and Vcr becomes large, so that the creeping dielectric breakdown voltage becomes high.

Where dC / dxL is

[0024]

[Equation 2]

Can be expressed as At this time, εo: permittivity of vacuum, εr: relative permittivity, f: coefficient of field strain, about 0.5, k: thickness of dielectric material, R: radius of conductive foreign matter,
It is. Therefore, when the diameter of the conductive foreign matter is 0.45 mm, a low dielectric constant material of 3 mm, which is at least 10 times the radius of the foreign matter or more, is required to improve the creeping breakdown voltage when the foreign matter adheres.
A thin coating film cannot fulfill its function.

Therefore, in the insulating spacer according to the present embodiment, the dielectric strength at the time of adhering foreign matter is improved, and in the high dielectric constant material portion excellent in mechanical strength, as compared with the single-layer spacer having a dielectric constant of about 5. Since it supports the load, it has higher strength than the spacer composed of a single layer of low dielectric constant material.

FIG. 3 is a vertical sectional view of the insulating spacer 3 according to the second embodiment of the present invention. In this embodiment, in the epoxy resin cast with the embedded electrodes 5a and 5b,
By adjusting the amount of the inorganic filler 7 to be mixed, for example, in the epoxy resin filled with alumina (Al ₂ O ₃ ), the amount of the filler is adjusted so that the dielectric constant becomes 5 or more in the central portion as it approaches the peripheral portion. The dielectric constant is adjusted to be about 3.5 to 4.5 in the vicinity of the creeping surface by continuously decreasing it. That is, in the present embodiment, the central member 3a and the surface member 3b of the first embodiment are integrally formed, and the coupling agent is unnecessary. Similar to the first embodiment, this embodiment also has the effect of increasing the mechanical strength in the high dielectric constant portion of the central portion and increasing the creeping dielectric strength in the peripheral low dielectric constant portion. Comparing the first embodiment and the second embodiment, the second embodiment is more difficult to manufacture and costs more, but the reliability of the insulation resistance is high because there is no interface between the members 3a and 3b of the first embodiment. It can be said that it has high sex.

The above is an example in which the insulating spacer 3 is applied. Of course, the cone type insulating spacer 4 shown in FIG.
The same measures as those in the above-described example are applied, and a thick low dielectric constant plate material is bonded to both entire surfaces of the cone with a silane coupling agent interposed, or the mixing ratio of the inorganic filler is controlled to permit the dielectric constant. Needless to say, the lower the dielectric constant, the lower the surface may become.

[0029]

According to the present invention, even if there is a conductive foreign substance that moves in an electric field in a metal container, sufficient insulation performance can be maintained, reliability is improved, and the device can be downsized. Play.

[Brief description of drawings]

FIG. 1 is a view of a gas-insulated switchgear according to a first embodiment of the present invention as seen from an axial direction (an insulating spacer portion is a cross-sectional view).

FIG. 2 is a vertical sectional view of the insulating spacer shown in FIG.

FIG. 3 is a vertical sectional view of an insulating spacer according to a second embodiment of the present invention.

FIG. 4 is a diagram showing an example of a busbar in the gas insulated switchgear.

[Explanation of symbols]

1 ... Metal container, 2 ... High-voltage conductor, 3a, 3b ... Insulating layer, 4
... Cone type insulating spacers, 5a, 5b ... Embedded electrodes, 6
... Lower support metal fittings, 7 ... Inorganic filler.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takuya Sugawara 7-2-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Electric Power & Electric Development Division

Claims (9)

[Claims] 1. An insulating spacer for insulating and supporting between a high-voltage conductor of a gas-insulated switchgear or a pipeline air transmission line and a hermetically sealed container that holds the high-voltage conductor in an airtight manner. An insulating spacer comprising: a member, a surface member that is disposed on the surface of the central member and is made of a low dielectric constant material, and a coupling agent that closely adheres the central member and the surface member. 2. The insulating spacer according to claim 1, wherein the center member has a dielectric constant of 5 or more and the surface member has a dielectric constant of 3.5 to 4.5. 3. The insulating spacer according to claim 1, wherein the surface member has a thickness of at least 3 mm. 4. An insulating spacer for insulating and supporting between a high-voltage conductor of a gas-insulated switchgear or a pipeline aerial power transmission line and a closed container that holds the high-voltage conductor in an airtight manner, wherein an inorganic material is filled in the insulating spacer. An insulating spacer characterized in that the surface portion has a lower density than the density of the filler. 5. The density of the inorganic filler according to claim 4, wherein the central part has a dielectric constant of 5 or more and the surface part has a dielectric constant of 3.5 to 4.5. Insulation spacer to be. 6. The dielectric constant according to claim 5, wherein the dielectric constant is 3.5.
An insulating spacer characterized in that the thickness of the surface portion of ~ 4.5 is at least 3 mm or more. 7. A gas-insulated switchgear comprising a hermetically sealed container in which an insulating gas is sealed, a high-voltage conductor inserted into the hermetically sealed container, and an insulating spacer for insulatingly supporting the high-voltage conductor in the hermetically sealed container. A gas-insulated switchgear, wherein the insulating spacer according to any one of claims 1 to 6 is used as the insulating spacer. 8. A pipeline gas comprising an airtight container in which an insulating gas is sealed, a high-voltage conductor inserted into the airtight container, and an insulating spacer for insulatingly supporting the high-voltage conductor in the airtight container. In a medium power transmission line, a pipeline air transmission line, wherein the insulating spacer according to any one of claims 1 to 6 is used as the insulating spacer. 9. A substation facility comprising the gas insulated switchgear according to claim 7 or the pipeline air transmission line according to claim 8.