JP2001016721A - Gas insulated electric apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure both of required dielectric strength after the commencement of operation and breakdown pressure during a test by mounting a dielectric strength improving means, based on the temperature distribution after a mixed gas is charged. SOLUTION: A dielectric strength improving means is mounted, based on the temperature distribution after mixed gas is charged, so as to stand pressure for test voltage while required dielectric strength is being ensured during operation. Upper SF6 gas concentration is lower than when it is uniform, and the dielectric strength lowers in a breaker 41, the insulation distance of an upper high voltage part 44 is made longer than that of the lower high voltage part 42, prevent the dielectric strength of the high voltage part 44 from lowering. By increasing the inclination of an insulating spacer 4d to increase creep distance, the dielectric strength is increased. Thus both the assurance of the required dielectric strength after the commencement of operation and pressure withstanding during a test are made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a gas insulated switchgear.
Involved in gas-insulated electrical equipment such as gas-insulated transformers.
The present invention relates to a gas-insulated electric device using a mixed gas composed of at least one kind of gas as an insulating gas.

[0002]

2. Description of the Related Art In the prior art, for example, Japanese Unexamined Patent Publication No.
As described in No. 832, by sealing an insulating mixed gas obtained by mixing SF ₆ gas and N ₂ or dry air or CO ₂ or the like in a gas-insulated electric device, the partial pressure of SF ₆ gas is reduced to cool down. Liquefaction of SF ₆ gas on the ground was prevented. At this time, the partial pressure of SF ₆ gas was 1 atm or more.

[0003]

In the above-mentioned conventional gas-insulated electric equipment, no consideration is given to the fact that the concentration distribution of the mixed gas after gas filling becomes non-uniform and the dielectric strength decreases depending on the portion.

FIG. 3 shows that N ₂ gas and SF ₆ are contained in a tank 80.
It is an example of the dielectric strength of each part when a gas is mixed and sealed. Immediately after mixing, since the concentration of SF ₆ gas having a large specific gravity is high in the lower part, the dielectric strength is higher in the lower part and lower in the upper part as compared with the case where it is uniform. This concentration distribution becomes uniform with time, but it takes several tens of hours to become uniform.

Therefore, in a gas insulated electric device, if a voltage is applied immediately after filling a mixed gas in a factory test, a field test, or the like, there has been a problem that insulation breakdown occurs and the reliability of the device is reduced. Conversely, if the dielectric strength is designed to be reduced, there is a problem that the equipment becomes large and the cost increases.

An object of the present invention is to provide a gas-insulated electric device which can secure both a required dielectric strength after the start of operation and a withstand voltage during a test and which is inexpensive and uses a mixed gas as an insulating gas. That is.

[0007]

In order to solve the above-mentioned problems, the gas-insulated electric equipment of the present invention is provided with means for improving the dielectric strength based on the concentration distribution after filling the mixed gas. The means for improving the dielectric strength include, for example, a partial increase in the insulation dimension, a partial decrease in the electric field concentration, and an increase in the creepage distance of the spacer.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment in which the present invention is applied to a gas insulated switchgear (hereinafter referred to as GIS). In FIG. 1, GIS is a main bus 1, a bus disconnector 11, a connection bus 2
1, CT unit 31, circuit breaker 41, line disconnector 5
1. It is configured by connecting device units such as grounding devices 6a, 6b, 6c and a cable head 61. FIG.
The GIS is one unit per line, and the GIS is usually configured by combining several units to several tens of units.

[0010] Ground tanks 7, 17, 4 of each equipment unit
Some such 7,57,67 is, SF ₆ / N ₂ mixed gas several% to several tens% of SF ₆ gas is sealed as the insulating gas. Then, high-voltage parts such as the conductor 2, an opening / closing part composed of the movable-side electrode 12 and the fixed-side electrode 13, and a blocking part composed of the movable-side electrode 42 and the fixed-side electrode 43 are arranged.
Spacers 4a, 4b, 4c, 4d, 4e, insulating cylinder 46,
It is insulated and supported by an insulator such as 56. Each electrode has
Shields are installed as needed. Further, each device unit is gas-divided by insulating spacers 4a to 4e.

In the present invention, for example, in the circuit breaker 41, the insulation distance L2 of the upper high-voltage part 44 is made longer than the insulation distance L1 of the lower high-voltage part 42 by 5 to 20%, so that The dielectric strength has been improved.
Further, in the present invention, the spacer 4a is arranged between the main bus 1 and the bus disconnector 11, thereby suppressing the unevenness of the gas concentration distribution.

Hereinafter, the reason why the above-described embodiment is adopted will be described.

[0013] In the conventional gas-insulated electrical equipment, from that dielectric strength is high pure SF ₆ (sulfur hexafluoride) gas, mainly SF ₆
Gas has been used as an insulating gas. However, in recent years, from the viewpoint of preventing global warming, it has been required to minimize the amount of SF ₆ gas used. As a countermeasure for this, for example, it is conceivable to use a gas having a global warming index of not more than carbon dioxide CO ₂ as a main gas and a gas obtained by slightly mixing a gas having a higher dielectric strength than the main gas as an insulating gas. Gases with a global warming index of less than CO ₂ include nitrogen N ₂ ,
There are air, CO _{2 and the} like, and SF ₆ gas is a gas having a higher dielectric strength than these gases. CFCs such as C ₃ F ₈ and c-C ₄ F ₈ also have a high dielectric strength. Then, a mixed gas of N ₂ and SF _6, a mixed gas of air and SF ₆ , and the like are easily put into practical use.

FIG. 2 shows an example of the dielectric strength characteristics of the SF ₆ / N ₂ mixed gas with respect to the SF ₆ gas mixture ratio. SF ₆
When the mixing ratio of the gas is small, the dielectric strength rapidly increases when the mixing ratio is increased. When the mixture ratio becomes 10% or more, the increase in the dielectric strength shows a tendency to be saturated. As described above, the characteristic becomes convex upward and is higher than the dielectric strength (broken line in FIG. 2) calculated simply by the partial pressure ratio. Therefore, it can be said that SF ₆ and N ₂ have a synergistic effect on the insulating characteristic. . From the characteristics of FIG. 2, by setting the mixing ratio of SF ₆ gas to several percent to several tens percent, it is possible to secure a high dielectric strength while suppressing the amount of SF ₆ gas used. However, in this region, since the fluctuation of the dielectric strength due to the fluctuation of the concentration is large, it is necessary to consider the fluctuation of the dielectric strength due to the uneven distribution of the concentration.

FIG. 3 shows an example of the dielectric strength of each part when N ₂ gas and SF ₆ gas are mixed and sealed in the tank 80. Immediately after mixing, since the concentration of SF ₆ gas is high in the lower part, the dielectric strength of the lower part is higher and the dielectric strength of the upper part is lower than in a uniform case. This is because the molecular weight 146 of SF ₆ is five times heavier than the molecular weight 28 of N ₂ .

This concentration distribution becomes uniform over time, but it takes several tens of hours to become uniform. For this reason,
In a gas insulated electric device, if a voltage is applied within several hours after filling a mixed gas in a factory test or on-site test, insulation breakdown occurs, and the reliability of the device is reduced. Conversely, if the insulation design is performed on the assumption that the dielectric strength is reduced, there is a problem that the device becomes large and the cost increases.

In the present invention, in order to ensure the required dielectric strength during operation and to withstand the test voltage, a means for improving the dielectric strength is provided based on the concentration distribution after filling the mixed gas. Specifically, in the concentration distribution after a certain period of time after filling the mixed gas, in a portion where the dielectric strength is lower than that in the case where the concentration distribution is uniform, a dielectric strength improving means such as increasing the insulation distance is taken. The fixed time includes, for example, a time from completion of gas filling in a factory test or a field acceptance test or a periodic inspection to application of a test voltage. The temporal change of the concentration distribution can be estimated by measuring a similar shape of the grounded tank.

In the circuit breaker 41 in the GIS shown in FIG.
Since the upper SF ₆ gas concentration may be lower than the case where the concentration is uniform and the dielectric strength may be reduced by 5 to 20%, the insulation distance L 2 of the upper high voltage part 44 is reduced to the insulation distance L 1 of the lower high voltage part 42. By increasing the length by 5 to 20%, the dielectric strength of the high voltage portion 44 is not reduced. The rate of decrease in the dielectric strength varies depending on the shape of the grounding tank, the time from the gas filling until the test is performed, and the like.

By the way, as described above, the insulation distances L1, L2
Is lengthened in accordance with the decrease in the dielectric strength when the electric field concentration in both portions is equal, but in practice, the electric field concentration often differs. In such a case, two or more sites with high electric field concentration are selected at n locations, the electric field concentration of the selected region is set to ξ1, ξ2... Ξn, the insulation distance is set to L1, L2. When the destructive electric field of each part in the concentration distribution after a certain period of time has elapsed since the encapsulation is E1, E2.

[0020]

.Times..times..times..times..times..times..times..times..times..times..tim- es..times..times..times..times..times. Here, it is necessary to consider both the case where the gas concentration is non-uniform and the case where the gas concentration is uniform. Therefore, depending on the case, the insulation distance L or the electric field concentration degree ξ may be reduced from the value determined by the equation (1). There are also (1)
The equation remains the basis for non-uniform gas concentrations. Hereinafter, the principle of such setting will be described.

When a high voltage is applied to a gas-insulated electric device to cause a flashover inside, the relationship between the breakdown electric field E at the flashover point and the flashover voltage (hereinafter referred to as FOV) is as follows.

[0022]

FOV / Lξ = E (2) Here, FOVi / Li is an average breakdown electric field, and the breakdown electric field Ei is higher than the average breakdown electric field by the electric field concentration degree Δi. Ei is a value determined by the insulating gas.
In the case of the F ₆ / N ₂ mixed gas, it changes depending on the SF ₆ gas concentration as shown in FIG. Therefore, when it is assumed that the flashover has occurred at each part i, the FOVi is

[0023]

FOVi = Ei · Li / ξi (3) Therefore, according to the equation (1), the FO of each unit is obtained.
V are equivalent, and the optimum insulation design is achieved.

When only the SF ₆ gas is used as the insulating gas in the GIS as shown in FIG. 1, an insulating spacer is often not inserted between the main bus 1 and the bus disconnector 11. However, when the mixed gas is an insulating gas, if the volume of the main bus 1 is large, SF ₆ gas molecules easily stay in the main bus 1.
Therefore, there is a possibility that the SF ₆ gas concentration is reduced in the bus disconnector 11 and the dielectric strength is reduced. Therefore, an insulating spacer is inserted between the main bus 1 and the bus disconnector 11 to reduce the unevenness of the SF ₆ gas concentration. It is possible to suppress the decrease of the dielectric strength.

FIG. 4 shows another embodiment in which the present invention is applied to a gas insulated switchgear. By making the radius of curvature R2 of the surface of the high voltage portion 44 larger than the radius of curvature R1 of the surface of the portion 42, L2 The electric field concentration degree ξ2 is reduced without increasing the dielectric strength to improve the dielectric strength.

When supporting a closing resistance element or the like, a post spacer 48 is disposed. However, the post spacer 48 is formed with a fold and the creepage length can be increased to improve the dielectric strength without increasing L2.

The cone-shaped insulation spacer 4c, 4d, since towards the convex side than the dielectric strength is high concave side, the reduction tends to top of the SF ₆ gas concentration, conical insulating spacer 4d
The dielectric strength is ensured by directing the convex side of. Further, by increasing the inclination of the insulating spacer 4d, the creepage length is increased, and the dielectric strength is improved.

FIG. 5 shows another embodiment in which the present invention is applied to a gas insulated switchgear.

By providing an insulating coating on the surface of the high voltage portion 44, the breakdown electric field E can be improved, so that the dielectric strength can be improved without increasing L2. Examples of the surface coating include an epoxy resin and a phthalic acid resin.

When the conductor is aluminum, an anodizing treatment (alumite treatment) is performed to provide an insulating oxide film to form an insulating coating, thereby improving the dielectric strength. This oxide film also improves the thermal emissivity of the surface,
If applied to the current-carrying conductor, the current capacity can be increased.

The insulating strength can be improved even if the insulating coating is stopped at the portion where the insulating coating is applied in FIG. 5 and the surface roughness is reduced.

As described above, when two kinds of gases are separately supplied to the tank, the gas is in a separated state even after a considerable time has passed since encapsulation. In portions where the concentration is low, the dielectric strength decreases. However, if two kinds of gases are uniformly mixed by a gas mixing device at the time of supply and then sealed, the mixed gas in the tank is uniform, so that the dielectric strength does not decrease.

FIG. 6 is a schematic diagram of one embodiment of the gas mixing device. In the gas mixing device shown in the figure, the SF ₆ gas cylinder 1
After the gas pressure of each of the 01 and N ₂ gas cylinders 102 is reduced by the pressure regulators 103 and 104, they are heated by the heat exchanger 105. Then, the two types of gases are mixed by stirring in the mixer 106, and temporarily stored in the storage tank 107.
From 7, a uniform mixed gas is supplied to the gas insulated switchgear 90.

In the above description, GIS is mainly described, but the present invention can also be applied to various gas-insulated electric devices such as a gas-insulated transformer using a mixed gas as an insulating gas.

[0035]

According to the present invention, a gas-insulated electric device which can secure both the required dielectric strength after the start of operation and the withstand voltage at the time of the test and which is inexpensive and uses a mixed gas as the insulating gas can be provided. Can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an embodiment in which the present invention is applied to a gas insulated switchgear.

FIG. 2 is a view for explaining the relationship between the mixing ratio of SF ₆ / N ₂ mixed gas and dielectric strength.

FIG. 3 is a diagram illustrating a change over time in the dielectric strength of each part after filling a mixed gas of SF ₆ / N ₂ into a tank.

FIG. 4 is a diagram illustrating an embodiment in which the present invention is applied to a gas insulated switchgear.

FIG. 5 is a diagram illustrating an embodiment in which the present invention is applied to a gas insulated switchgear.

FIG. 6 is a schematic view of an embodiment of a gas insulated switchgear provided with a gas mixing device.

[Explanation of symbols]

1 ... Main bus, 4a-4e ... Insulating spacer, 6a-6c ...
Grounding device, 11 Bus disconnector, 21 Connection bus, 31
CT unit, 41: circuit breaker, 51: line disconnector, 6
DESCRIPTION OF SYMBOLS 1 ... Cable unit, 100 ... Gas mixing device, 103
... Pressure regulator (for SF ₆ ), 104 ... Pressure regulator (N
₂ ), 105: heat exchanger, 106: mixer, 107 ...
Storage tank.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yoshitoyo Yagihashi 7-2-1, Omika-cho, Hitachi City, Ibaraki Prefecture F-term in the Electric Power & Electronics Development Division, Hitachi, Ltd. 5G017 DD01 DD06 EE06 HH01 HH04

Claims (12)

[Claims] 1. A grounding tank in which a mixed gas of two or more gases is filled as an insulating gas, a high-voltage part disposed in the grounding tank and having a conductor, a switch, and a shield; A gas-insulated electrical device comprising: a plurality of insulators which are insulated and supported; and a means for improving a dielectric strength based on a concentration distribution of the mixed gas after encapsulation. 2. A grounding tank in which a mixed gas of two or more gases is sealed as an insulating gas, a high-voltage part disposed in the grounding tank and having a conductor, a switch, and a shield; In a gas-insulated electrical device comprising a plurality of insulators for insulating support, a dielectric strength is defined at a portion where the mixed gas is sealed and the dielectric strength at a concentration distribution after a certain period of time becomes lower than when the concentration distribution is uniform. A gas-insulated electric device characterized by comprising means for improving the performance. 3. The gas-insulated electric device according to claim 1, wherein the mixed gas is a first gas having a global warming index smaller than carbon dioxide CO ₂ and a first gas having a dielectric strength equal to the first gas.
A gas insulated electric device comprising: a second gas higher than a second gas; and a means for improving the dielectric strength provided at a portion where the concentration of the second gas can be low. 4. The gas-insulated electrical device according to claim 3, wherein the first gas is nitrogen N ₂ or air or carbon dioxide gas CO ₂ , and the second gas is sulfur hexafluoride SF _6. or gas-insulated electric device, which is a chlorofluorocarbon, such as _{C 3 F 8, c-C} 4 F 8. 5. The gas-insulated electric device according to claim 3, wherein a means for improving the dielectric strength is provided in an upper part of the grounding tank. machine. 6. A ground tank in which a mixed gas of two or more gases is sealed as an insulating gas, a high-voltage part disposed in the ground tank and having a conductor, a switch, and a shield; In a gas insulated electric device provided with a plurality of insulators to be insulated and supported, two or more portions having a high electric field concentration are selected from the one having the highest concentration, the number of the selected portions is n, and the electric field of the selected portion is n. The concentration level is ξ1, ξ2… ξ
n, the insulation distances of the respective portions are L1, L2... Ln, and the breakdown electric fields of the respective portions are E1, E2. 1. A gas-insulated electric device characterized by satisfying the following relationship: E1 · L1 / ξ1 = E2 · L2 / ξ2 =... = En · Ln / ξn. 7. The gas-insulated electric device according to claim 1, wherein the means for improving the dielectric strength is by increasing an insulation distance or a high-voltage electrode of the insulator. By increasing the creeping length from the ground electrode to the ground electrode, or by providing an insulating coating on the surface of the high-voltage part, or by reducing the surface roughness of the high-voltage part, or of the high-voltage part Gas insulated electrical equipment characterized by increasing the radius of curvature of the electrode surface. 8. A ground tank in which a mixed gas of two or more gases is filled as an insulating gas, a high-voltage part disposed in the ground tank and having a conductor, a switch, and a shield; What is claimed is: 1. A gas insulated electric device comprising: a plurality of insulators that are insulated and supported; and a means for suppressing non-uniformity in the concentration of the mixed gas. 9. The gas-insulated electric device according to claim 8, wherein the means for suppressing the non-uniformity of the concentration of the mixed gas includes:
A gas-insulated electric device characterized in that the grounding tank is vertically separated by the insulator. 10. A ground tank in which a mixed gas composed of two or more gases is sealed as an insulating gas, a high-voltage part disposed in the ground tank and having a conductor, a switch, and a shield; What is claimed is: 1. A gas-insulated electrical device comprising: a plurality of insulators that are insulated and supported; and a gas-mixing device for uniformly mixing and supplying the two or more gases. 11. The gas-insulated electric device according to claim 10, wherein the gas mixing device includes a gas cylinder filled with each of the two or more gases, and a pressure regulator for reducing a gas pressure of each of the gas cylinders. A heat exchanger for warming the gas discharged from the pressure regulator, a mixer for mixing two or more gases heated by the heat exchanger, and a gas mixed by the mixer. A gas-insulated electrical device comprising a storage tank for temporarily storing the gas. 12. The gas-insulated electric device according to claim 2, wherein the predetermined time is a time from completion of gas filling in a factory test, an on-site acceptance test, or a periodic inspection to application of a test voltage. Gas insulated electrical equipment.