JP7137486B2 - Gas-insulated switchgear and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a gas-insulated switchgear and a manufacturing method thereof.

In a gas-insulated switchgear, main circuit devices such as power receiving disconnectors, circuit breakers, and busbar disconnectors are housed in a sealed container containing an insulating gas such as sulfur hexafluoride (SF ₆ ). Each device is connected by a main circuit conductor. The main circuit conductor is supported in the gas by an insulator installed in the container, and maintains insulation from the sealed container at ground potential.

In a gas-insulated switchgear for power reception, power is drawn from the power system through a power cable or an overhead line, and supplied to the bus via a power receiving disconnector-circuit breaker-bus disconnector. In the case of a gas-insulated switchgear for power supply, power is received from the busbar and supplied to the power cable or overhead line connected to the load via the disconnector for the busbar - the circuit breaker - the disconnector for power supply. A busbar electrically connects a gas-insulated switchgear that constitutes one bay with three phases as one line and a gas-insulated switchgear that constitutes an adjacent one bay.

In a gas-insulated switchgear having a closed container containing an insulating gas and a main circuit conductor housed inside the closed container, a resin layer containing a nonlinear resistance material is formed on the inner surface of the closed container. In addition, it is being studied to solve the problem that a high electric field is generated around metallic foreign matter generated inside a closed container, causing the metallic foreign matter to float.

Patent Document 1 discloses a grounding tank filled with an insulating gas, a center conductor placed inside the grounding tank, and a nonlinear resistance material placed on the lower inner surface of the grounding tank, and the insulating material contains a nonlinear resistance material. A gas insulated switchgear is disclosed having a non-linear resistance section comprising more non-linear resistance material on the center conductor side compared to the ground tank side. This document describes that the above configuration can suppress partial discharge in the vicinity of the metal foreign matter mixed in the ground tank, and can also suppress the inflow of charges from the ground tank to the metal foreign matter. .

WO2015/136753

A high electric field around metallic foreign matter generated inside a closed container of a gas-insulated switchgear and floating of the metallic foreign matter lead to the occurrence of corona discharge and streamer discharge inside the closed container, a decrease in dielectric strength, and the like.

In Patent Document 1, electric field-conductivity characteristics that differ depending on the type of nonlinear resistance material are not sufficiently studied.

A material with a low electric field in which nonlinearity appears has a gradual increase in conductivity, a small relaxation effect in a high electric field region, and a partial discharge is likely to occur. In addition, a material with a steep rate of increase in conductivity has a relatively high electric field in which nonlinearity appears, and the relaxation effect at low electric fields is small, resulting in large variations in suppression of partial discharge.

SUMMARY OF THE INVENTION It is an object of the present invention to reliably suppress floating of metallic foreign matter generated inside a gas-insulated switchgear and adhering to the inner surface of a tank, thereby maintaining high dielectric strength.

The gas-insulated switchgear of the present invention has a grounded tank and a high-voltage conductor installed inside the tank and insulated from the tank. A resin layer having a configuration in which resistance materials are mixed is formed, and the first nonlinear resistance material, which is at least one of the plurality of types of nonlinear resistance materials, is at least one of the plurality of types of nonlinear resistance materials. The operating electric field is higher than that of the second nonlinear resistive material, which is another nonlinear resistive material of the type, and the slope of the nonlinear characteristic curve is steeper in the range of the electric field higher than the operating electric field.

Advantageous Effects of Invention According to the present invention, it is possible to reliably suppress floating of metallic foreign matter generated inside a gas-insulated switchgear and adhering to the inner surface of a tank, and to maintain high dielectric strength.

1 is a partial cross-sectional view showing the overall configuration of a gas-insulated switchgear according to the present invention; FIG. It is a schematic cross section showing a part of the tank of the gas insulated switchgear of the present invention. 3 is a cross-sectional view showing an example of arrangement of a resin layer 53 of FIG. 2; FIG. 4 is a graph showing electric field-conductivity characteristics of zinc oxide, which is a nonlinear resistance material. 4 is a graph showing electric field-conductivity characteristics of silicon carbide, which is a nonlinear resistance material. 4 is a graph showing electric field-conductivity characteristics when two types of nonlinear resistance materials are mixed. 4 is a graph showing the electric field-conductivity characteristics when the additive amount of the nonlinear resistance material is used as a parameter. It is a graph which shows the result of the levitation test in the case of installing a metal foreign substance in a tank. It is a flow figure showing an example of a formation process of a resin layer of the present invention.

TECHNICAL FIELD The present invention relates to a coating technology for the inside of a tank of a gas-insulated switchgear. The present invention relates to coating of a nonlinear resistance material inside a tank used in a gas insulated switchgear having a power supply unit installed in an insulated container and supplying electric power to the load side via a bus.

Hereinafter, the present invention will be described with reference to the drawings.

FIG. 1 is a partial cross-sectional view showing the overall configuration of a gas-insulated switchgear according to the present invention.

In this figure, the gas-insulated switchgear 100 includes a ground tank 2 (hereinafter also simply referred to as "tank") filled with an insulating gas (SF6, etc.) and a high _- voltage conductor provided inside the ground tank 2. 1 and an insulating spacer 30 (hereinafter also simply referred to as “spacer”) for supporting and fixing the high-voltage conductor 1 inside the ground tank 2 . In addition, the gas-insulated switchgear 100 includes a circuit breaker 20, a disconnecting switch 21, an earthing switch 22, a current transformer 23, a transformer 24, buses 25 and 26, and the like. Dry air is also used as the insulating gas with which the tank is filled.

The high-voltage conductor 1 is made of cylindrical metal (aluminum, copper, or the like). The ground tank 2 is a cylindrical metal container. The high-voltage conductor 1 is supported and fixed inside the ground tank 2 by an insulating spacer 30 and is insulated from the ground tank 2 . Since the ground tank 2 is grounded, the potential is normally zero.

Although a cone-shaped spacer (cone spacer) is shown as the insulating spacer 30 in FIG.

FIG. 2 is a schematic cross-sectional view showing part of the tank of the gas-insulated switchgear of the present invention.

As shown in this figure, a resin layer 53 is provided on the inner surface of the tank wall 51 . The resin layer 53 is formed by coating a mixture of epoxy resin or the like with the nonlinear resistance materials 121 and 122 added thereto. Zinc oxide (ZnO), silicon carbide (SiC), barium titanate (BaTiO ₃ ), diamond, or the like is used as the nonlinear resistance materials 121 and 122 .

That is, in the present invention, the nonlinear resistance materials 121 and 122 are particulate and consist of two or more different compositions.

Note that foreign matter 54 (metallic foreign matter) may adhere to the inner surface of the tank wall 51 .

FIG. 3 is a cross-sectional view showing an example of arrangement of the resin layer 53 of FIG.

In this figure, a resin layer 53 is provided on the lower half region of the inner surface of the tank wall 51 . A resin (epoxy resin or the like) that does not contain a nonlinear resistance material is applied to the upper half region of the inner surface of the tank wall 51 to form a resin layer 131 (insulating resin layer). Metallic foreign matter often falls downward due to gravity, so it is often sufficient to provide the resin layer 53 in the lower half region. Also, by partially providing the resin layer 53 in this manner, the manufacturing cost can be suppressed.

Of course, the resin layer 53 may also be provided on the upper half region of the inner surface of the tank wall 51 . In some cases, the resin layer 53 may be provided on the entire lower half area and part of the upper half area. The resin layer 53 is desirably provided over at least the entire area of the lower half.

Next, functions and effects of the resin layer 53 including the nonlinear resistance materials 121 and 122 will be described with reference to FIG.

When foreign matter 54 (metallic foreign matter) occurs inside the tank, the electric field concentrates in the vicinity of the foreign matter 54, resulting in a high electric field. When the electric field to the nonlinear resistance materials 121 and 122 in this range increases, the electrical conductivity of the nonlinear resistance materials 121 and 122 increases, which is electrically equivalent to expanding the size of the tip of the foreign matter 54 . Electric field concentration in the vicinity is relaxed. This relaxation improves the dielectric strength when the foreign matter 54 adheres.

It should be noted that the thickness of the resin layer 53 is preferably 50 μm or more. The thickness of the resin layer 53 is desirably 1 mm or less, more desirably 200 μm or less, from the standpoint of the size inside the tank, material costs, and the like.

Examples are described below.

FIG. 4 is a graph showing electric field-conductivity characteristics of zinc oxide, which is an example of a nonlinear resistance material. The horizontal axis is the electric field, and the vertical axis is the conductivity. The concentration of zinc oxide in the resin layer is 10% by mass.

As shown in this figure, zinc oxide has nonlinear electric field-conductivity characteristics (nonlinear characteristics). In the case of zinc oxide, the electric field at which the sharp rise of the electric field-conductivity curve begins (hereinafter referred to as the "operating electric field") is about 7 kV/mm. That is, in the case of zinc oxide, when the electric field reaches about 7 kV/mm, the slope of the nonlinear characteristic curve (hereinafter also simply referred to as "curve") becomes steeper, the curve rises, and the electrical conductivity rises sharply.

As an example of a more rigorous definition of the "operating electric field", the value of the electric field at which the slope change rate (second derivative) of the curve begins to increase beyond a predetermined value may be used. In this case, the operating electric field can be calculated by expressing the approximation of the curve by a Taylor polynomial of degree 3 or higher and calculating the second derivative.

The operating electric field varies not only with the type of nonlinear resistance material, but also with the concentration of the nonlinear resistance material in the resin. Therefore, when comparing the operating electric fields of different types of non-linear resistance materials, in this specification, non-linear characteristic curves measured by mixing materials with the same concentration on the mass basis and the same resin are compared. . Therefore, it is possible to express that the first nonlinear resistance material has a higher operating electric field than the second nonlinear resistance material, and that the slope of the nonlinear characteristic curve is large in the range of the electric field higher than the operating electric field.

FIG. 5 is a graph showing electric field-conductivity characteristics of silicon carbide, which is a nonlinear resistance material. The concentration of silicon carbide in the resin layer is 10% by mass.

As shown in this figure, in the case of silicon carbide, the operating electric field is low and the slope of the curve is relatively gentle. The rise of the curve (operating electric field) is about 4 kV/mm, and the slope of the curve becomes gentle at about 8 kV/mm or more.

FIG. 6 is a graph showing electric field-conductivity characteristics when two types of nonlinear resistance materials are mixed. The concentration of zinc oxide in the resin layer is 10% by mass, and the concentration of silicon carbide is 10% by mass.

In this figure, due to the action of silicon carbide having a low operating electric field, the slope of the curve begins to increase at about 4 kV/mm and further increases at about 7 kV/mm and above.

As a result, the electric field around the foreign object is relaxed from the state where the applied voltage is low. Moreover, a sufficient electric field relaxation effect can be obtained at a high voltage. Since the operating electric field is lowered, variations in electric field relaxation are reduced, and foreign matter levitation can be prevented at a low voltage. In addition, since the slope of the nonlinear characteristic curve becomes large, the electric field relaxation effect at high voltage becomes large, so that partial discharge can be prevented and the levitation electric field of the foreign matter can be increased.

The resin (coating material) containing the nonlinear resistance material is applied to the inner surface of the tank wall 51 by spray coating or brush coating.

In summary, from FIGS. 4 and 5, it can be seen that the first nonlinear resistance material, zinc oxide, has a higher operating electric field than the second nonlinear resistance material, silicon carbide. It can be said that the slope of the characteristic curve is large. The curve in FIG. 6 then has a shape in which the curves in FIGS. 4 and 5 are superimposed. This provides a suitable conductivity and operating electric field.

The operating electric field of the resin layer of this embodiment is preferably 3 kV/mm or more. This is because if the operating electric field is too low, the insulating function of the resin layer will be insufficient. Further, it is desirable that the operating electric field of the resin layer of this embodiment is 5 kV/mm or less. The operating electric field of the resin layer corresponds to the desired range of the operating electric field of the second non-linear resistance material.

FIG. 7 is a graph showing electric field-conductivity characteristics when the additive amount of the nonlinear resistance material is used as a parameter.

In this figure, zinc oxide and silicon carbide were added so that the concentrations of zinc oxide and silicon carbide in the resin layer were equal, and the respective concentrations were 5% by mass, 10% by mass, and 15% by mass. That is, when the concentration of zinc oxide is 5% by mass and the concentration of silicon carbide is 5% by mass (each 5% by mass), when the concentration of zinc oxide is 10% by mass and the concentration of silicon carbide is 10% by mass ( 10% by mass each), and a concentration of zinc oxide of 15% by mass and a concentration of silicon carbide of 15% by mass (15% by mass each).

As shown in this figure, the electric field-conductivity characteristics of the coating material change depending on the amount of the nonlinear resistance material added. Specifically, the beginning of the rise of the curve (operating electric field) is about 7 kV/mm for 5 wt% each, about 5 kV/mm for 10 wt% each, and about 4 kV/mm for 15 wt% each.

Therefore, if the amount of the nonlinear resistance material added is small, and if foreign matter exists on the inner surface of the tank wall, the increase in conductivity during electric field concentration may be insufficient, and the electric field may not be alleviated.

In order to solve the above problems, the total amount of the multiple types of non-linear resistance materials added is in the range of 5% by mass to 50% by mass. It is suitable for The amount of the non-linear resistance material added is more preferably in the range of 5% to 20% by mass, and particularly preferably in the range of 5% to 15% by mass.

In addition, the mixing ratio of the nonlinear resistance material with a low operating electric field (eg silicon carbide) and the nonlinear resistance material with a high operating electric field (eg zinc oxide) is between 1:4 and 4:1. It is suitable because it has the characteristics and the electric field relaxation effect occurs around the foreign matter. More preferably, the mixing ratio is between 1:3 and 3:1, particularly preferably between 1:2 and 2:1.

FIG. 8 is a graph showing the results of a floating test when metal foreign matter is placed in the tank. The vertical axis is the relative value of the breakdown voltage. Here, the breakdown voltage is the voltage at which metallic foreign matter floats under predetermined conditions. This voltage is also referred to as a metal foreign matter floating voltage.

In this figure, the value of the levitation electric field of foreign matter is 1.0 when the inner surface of the tank wall is a metal surface (no coating). When covered with an insulating film made only of resin (resin coating), the floating electric field has an average value of about 1.3 and a variation of about 20%.

Also, when a coating material containing zinc oxide alone is applied (nonlinear resistance material coating (single substance)), the average value is as high as about 1.5, but the variation is about 20%, which is equivalent to that of resin coating.

On the other hand, when the coating material added with two types of nonlinear resistance materials (zinc oxide and silicon carbide) is applied (nonlinear resistance material coating (mixed)), the average value of the levitation electric field is 1 0.6 or more, and the variation is as small as about 5%. This means that the smaller the variation, the higher the average value, and the metal foreign matter does not float at a low voltage. As a result, even if metallic foreign matter exists inside the tank, floating of the metallic foreign matter can be restricted and high dielectric strength can be maintained.

In addition, if two types of non-linear resistance materials are divided into one type each to prepare a coating material and apply it to the inner surface of the tank, when two resin layers are stacked, the non-linear resistance that comes into contact with metal foreign matter Since it is strongly influenced by the properties of the material, it is not possible to obtain the effects of this embodiment.

FIG. 9 is a flow chart showing an example of the resin layer forming process of the present invention.

As shown in the figure, first, a surface treatment agent and a nonlinear resistance material are mixed (S101). This mixture is added to the resin (S102). This is stirred (S103). This prevents agglomeration of the non-linear resistance material, resulting in a coating material in which the non-linear resistance material is uniformly dispersed. An example of the surface treatment agent is a silane coupling agent. Further, in step S102 or S103, a resin curing agent is also mixed.

The coating material after stirring is applied to the inner surface of the tank wall with a spray gun (S104). The applied coating material is cured under predetermined conditions (S105).

By using the surface treatment agent in step S101, the nonlinear resistance material is uniformly dispersed in the resin after the stirring in step S103. Therefore, in the range where the coating material is applied, the effect of alleviating the electric field around the metallic foreign matter becomes effective. This stabilizes the effect of improving the levitation electric field of the metallic foreign matter. The amount of the surface treatment agent to be added is preferably in the range of 0.1% by mass to 5% by mass.

The coating material may be applied to the inner surface of the tank after applying a single insulating resin containing no non-linear resistance material as an undercoat to the inner surface of the tank. In this case, it is desirable to apply the insulating resin alone, cure it once, and then apply the coating material to the coated surface. As a result, the insulating resin layer formed by undercoating prevents charge from being charged from the tank to the foreign matter, and the resin layer containing the non-linear resistance material makes it possible to alleviate electric field concentration and suppress partial discharge.

The thickness of the insulating resin layer is preferably 30 μm or more. Also, the thickness of the resin layer (coating layer) containing the nonlinear resistance material is preferably 50 μm or more. The thickness of each of these layers is desirably 1 mm or less, more desirably 200 μm or less, from the viewpoint of the dimensions inside the tank, material costs, and the like. This upper limit is the same for the case of only the coating layer.

1: high voltage conductor, 2: grounding tank, 20: circuit breaker, 21: disconnector, 22: grounding switch, 23: current transformer, 24: transformer, 25, 26: busbar, 30: insulating spacer, 51 : tank wall, 53: resin layer, 54: foreign matter, 100: gas-insulated switchgear, 121, 122: non-linear resistance material, 131: resin layer.

Claims (22)

a grounded tank; and
a high voltage conductor located within said tank and insulated from said tank;
A resin layer having a configuration in which a plurality of types of nonlinear resistance materials are mixed in a resin is formed on the inner surface of the tank,
A first nonlinear resistance material that is at least one type of nonlinear resistance material among the plurality of types of nonlinear resistance materials, and a second nonlinear resistance material that is at least one other type of nonlinear resistance material among the plurality of types of nonlinear resistance materials The operating electric field is higher than that of the resistive material, and the slope of the nonlinear characteristic curve is large in the range of the electric field higher than the operating electric field,
The total amount of the plurality of types of nonlinear resistance materials added is in the range of 5% by mass to 50% by mass,
A gas-insulated switchgear , wherein a mixing ratio of the first non-linear resistance material and the second non-linear resistance material is in the range of 1:4 to 4:1 . 2. The gas insulated switchgear according to claim 1, wherein said resin layer contains a surface treatment agent. 3. The gas insulated switchgear according to claim 2 , wherein the amount of said surface treatment agent added is in the range of 0.1% by mass to 5% by mass. 2. The gas-insulated switchgear according to claim 1, wherein said resin layer has a thickness of 50 [mu]m or more and 1 mm or less. 2. The gas insulated switchgear according to claim 1, wherein an insulating resin layer not containing said nonlinear resistance material is provided between said inner surface of said tank and said resin layer. 6. The gas-insulated switchgear according to claim 5 , wherein said insulating resin layer has a thickness of 30 [mu]m or more and 1 mm or less. 7. The gas insulated switchgear according to claim 6 , wherein said resin layer has a thickness of 50 [mu]m or more and 1 mm or less. 2. The gas insulated switchgear according to claim 1, wherein said nonlinear resistance material is two or more selected from the group consisting of zinc oxide, silicon carbide, barium titanate and diamond. The first nonlinear resistance material is zinc oxide,
2. The gas insulated switchgear according to claim 1, wherein said second nonlinear resistance material is silicon carbide. 2. The gas insulated switchgear according to claim 1, wherein said operating electric field of said second nonlinear resistance material is 3 kV/mm or more and 5 kV/mm or less. 2. The gas insulated switchgear according to claim 1, wherein said resin layer is formed on at least a lower half region of said inner surface of said tank. a grounded tank; and
a high voltage conductor located within said tank and insulated from said tank;
A resin layer having a configuration in which a plurality of types of nonlinear resistance materials are mixed in a resin is formed on the inner surface of the tank,
A first nonlinear resistance material that is at least one type of nonlinear resistance material among the plurality of types of nonlinear resistance materials, and a second nonlinear resistance material that is at least one other type of nonlinear resistance material among the plurality of types of nonlinear resistance materials A method for manufacturing a gas-insulated switchgear having an operating electric field higher than that of a resistive material and having a large slope of a nonlinear characteristic curve in a range of an electric field higher than the operating electric field, comprising:
mixing the resin and the plurality of types of nonlinear resistance materials to produce a coating material;
applying the coating material to the inner surface of the tank;
curing the coating material to form the resin layer ,
The total amount of the plurality of types of nonlinear resistance materials added is in the range of 5% by mass to 50% by mass,
A method of manufacturing a gas-insulated switchgear , wherein the mixing ratio of the first nonlinear resistance material and the second nonlinear resistance material is in the range of 1:4 to 4:1 . 13. The method of manufacturing a gas insulated switchgear according to claim 12 , wherein the plurality of kinds of nonlinear resistance materials are mixed with a surface treatment agent, and then further mixed with the resin to produce the coating material. 14. The method of manufacturing a gas insulated switchgear according to claim 13 , wherein the amount of said surface treatment agent added is in the range of 0.1% by mass to 5% by mass. 13. The method of manufacturing a gas insulated switchgear according to claim 12 , wherein the resin layer has a thickness of 50 [mu]m or more and 1 mm or less. 13. The gas insulation according to claim 12 , wherein an insulating resin layer is formed by applying an insulating resin alone that does not contain the nonlinear resistance material to the inner surface of the tank, and then the coating material is applied to the surface of the insulating resin layer. A method for manufacturing a switchgear. 17. The method for manufacturing a gas-insulated switchgear according to claim 16 , wherein the thickness of said insulating resin layer is 30 [mu]m or more and 1 mm or less. 18. The method of manufacturing a gas insulated switchgear according to claim 17 , wherein the resin layer has a thickness of 50 [mu]m or more and 1 mm or less. 13. The method of manufacturing a gas insulated switchgear according to claim 12 , wherein said nonlinear resistance material is two or more selected from the group consisting of zinc oxide, silicon carbide, barium titanate and diamond. The first nonlinear resistance material is zinc oxide,
13. The method of manufacturing a gas insulated switchgear according to claim 12 , wherein said second nonlinear resistance material is silicon carbide. 13. The method of manufacturing a gas insulated switchgear according to claim 12 , wherein said operating electric field of said second nonlinear resistance material is 3 kV/mm or more and 5 kV/mm or less. 13. The method of manufacturing a gas insulated switchgear according to claim 12 , wherein said resin layer is formed on at least a lower half region of said inner surface of said tank.

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