JPH0233818A - Gas insulated switchgear - Google Patents

Abstract

PURPOSE:To prevent the trap of a metal foreign material to a high voltage conductor due to a switching operation with a simple means and restrain the occurrence of straight polarity voltage by maintaining the predetermined relationship of field strength between the side of arc occurrence and a load side electrode. CONSTITUTION:A metal container 6 with an insulation gas 7 sealed therein is provided with a power supply side shield electrode 1 including the movable electrode 5 of arc occurrence side supported on an insulation spacer 8, and a load side shield electrode 2 opposed thereto. The radius of curvature of the surface of the aforesaid electrode 3 is so constituted as to be smaller than the radius of curvature of the electrode 2, and field strength on the surface of the electrode 3 is so set as to be larger than field strength on the surface of the electrode 2. Due to the aforesaid electrical asymmetry, the residual voltage of a load side bus bar becomes straight polarity and extremely small. As a result, the trap of a metal foreign material to a high voltage conductor due to a switching operation is prevented with a simple means and the occurrence of straight polarity surge voltage is restrained.

Description

Detailed Description of the Invention [Purpose of the Invention (Industrial Field of Application) The present invention relates to gas insulated switchgear used in power transmission and substations, and in particular to electrodes of switchgear such as disconnectors or circuit breakers. This relates to gas-insulated switchgear with improved structure.

(Prior art) Gas-insulated switchgear takes advantage of the excellent insulation performance and arc-extinguishing performance of insulating scum such as SF6 gas to provide circuit breakers, disconnectors, and grounding devices necessary for switching operations in power transmission and substations. , instrument transformers, lightning arresters, cable heads, bus bars, and other components are housed in a sealed metal container. These devices are supported and fixed to the metal container by insulating spacers, and are are connected to each other by high voltage conductors.

In recent years, such gas-insulated switchgear has been becoming smaller in size, but on the other hand, there have been the following problems. That is, while SF6 gas sealed inside a metal container has excellent insulating performance, it is known that its insulating performance deteriorates significantly in areas where the electric field is locally strong, so-called unequal electric field areas. ing.

In particular, if a foreign metal object gets into the metal container for some reason, an unequal electric field will be formed, and the foreign object itself will move around inside the device while receiving electrical force, causing a high voltage to be applied. It could adhere to the surface of busbars and insulators, causing dielectric breakdown. Such problems are becoming increasingly important as devices become smaller.

Therefore, in order to prevent such dielectric breakdown accidents caused by foreign metal objects, conventional methods have been to install a trap device in a part of the metal container, apply a coating to the inner surface of the metal container, or install a trap device on the shield electrode of a high voltage conductor. Efforts have been made to prevent the insulation performance from deteriorating even if metal foreign matter gets mixed in by providing a device.

(Problem to be Solved by the Invention) However, in recent years, metal foreign matter that has entered the gas insulated switchgear has been caused by the negative polarity DC voltage remaining in the load side fn line as the switch opens and closes, causing it to become a high voltage conductor. It has been revealed that there is a unique phenomenon called being trapped.

That is, if a negative polarity DC voltage remains on the load-side bus bar and a cheap metal is trapped in the high-voltage conductor, a problem arises in that dielectric breakdown is likely to occur due to the surge voltage accompanying the opening/closing operation.

In particular, since the breakdown voltage for positive surge voltages is lower than the breakdown voltage for negative surge voltages, there is a problem to be solved in that the generation of positive surge voltages must be suppressed.

The present invention was proposed in order to eliminate the above-mentioned drawbacks, and its purpose is to prevent metallic foreign matter from wrapping around a high voltage conductor that occurs during the opening/closing operation of a gas insulated switchgear, and to An object of the present invention is to provide a gas-insulated switchgear that can suppress the generation of positive surge voltage.

[Structure of the Invention (Means for Solving the Problems) The present invention includes a disconnector or a circuit breaker in which an insulating gas is sealed inside a hermetically sealed metal container and which has an opening/closing part consisting of two opposing electrodes. In the gas-insulated switchgear, the electric field strength on the surface of the electrode connected to the power supply side and where an arc occurs is greater than the electric field strength of the electrode connected to the load side.

(Function) According to the gas insulated switchgear of the present invention, the residual voltage generated on the load-side bus bar during the opening/closing operation can always be a positive polarity DC voltage. Even if metal foreign matter exists, it can be prevented from being trapped in the high voltage conductor.

Moreover, the upper limit value of the positive surge voltage at the time of restriking can be suppressed.

(Example) Hereinafter, an example of the present invention will be specifically described based on FIGS. 1 to 4.

(1) First Embodiment This embodiment describes a disconnector, and as shown in FIG. 1, a power supply side shield electrode 1 is supported and fixed within a metal container 6 by an insulating spacer 8. Furthermore, a movable electrode 3 connected to a power source 10 is disposed inside the shield electrode 1 .

On the other hand, a shield electrode 2 connected to the load side is arranged opposite to the shield electrode 1 on the power source side, and current switching operation is performed by the movable N pole 3 and the load side shield electrode 2.

Further, an insulating gas 7 such as SF6 gas is sealed inside the metal container 6.

Further, the radius of curvature of the surface of the movable electrode 3 on which the arc occurs is smaller than the radius of curvature of the load-side shield electrode 2 disposed opposite to it. this is,
This is because the electric field strength on the electrode surface of the movable electrode 3 is set to be greater than the electric field strength on the electrode surface of the load-side shield electrode 2 arranged opposite to each other.

Note that the electric field strength on the electrode surface varies depending on the shape and size of the movable electrode and shield electrode, the tank diameter, etc., so it is necessary to calculate the electric field strength on the electrode surface by performing numerical electric field calculations for each case. There is.

In the gas insulated switchgear of this embodiment having such a configuration, the residual voltage can be controlled as follows.

Generally, the ratio of the electric field strengths of opposing picture electrodes is called directional asymmetry, but it is known that the discharge voltage generated between electrodes with such electrical asymmetry varies depending on the polarity of the applied voltage. ing. For example, like a disconnector, it has electrical asymmetry and one electrode is connected to the power supply,
If the other electrode is a capacitive load, S, A, B
OCl(is set, ai.

Disconnect 5w1tch Induc
ed transients and traps
ped Charge in Ga5-In5u
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rans, on PAS Vol, PAS-101,
As shown in No. tO, p3593.1982, a special waveform called a staircase waveform appears on the load-side bus bar, and a DC voltage remains when the disconnection is completed by the disconnector.

It is known that the magnitude and polarity of such DC voltage, ie, residual voltage, differ depending on the electrode structure of the disconnector. Therefore, it is possible to control this residual voltage by adopting an appropriate electrode structure and opening speed of the disconnector.

For example, the results of determining the frequency of occurrence of the polarity and magnitude of the residual voltage when the electrical asymmetry is 15%, the electrical opening speed is 2 pLl/S, and the discharge variation σ is 10% are as follows:
It is shown in Figure 2. That is, the polarity of the residual voltage in this case is positive, and the magnitude difference of most of the residual voltages is 0.5 pu.
It turns out that the following is true.

Further, FIG. 3 shows the results of determining the relationship between the electrode opening speed and the electrical asymmetry of the electrode, which can be controlled so that the residual voltage becomes positive. In the region above the solid line or broken line shown in the figure, it is possible to make the residual voltage positive.

That is, in order to make the residual voltage positive, it is necessary to increase the electrical asymmetry of the electrodes as the opening speed increases.

In this way, according to this embodiment, it is possible to always maintain the positive polarity of the residual voltage on the load-side bus, so that it is possible to prevent metal foreign objects from being trapped in the high-voltage conductor.
Even when metal foreign matter is mixed in, it is possible to prevent a decrease in dielectric breakdown voltage.

In addition, since the voltage remaining on the load side bus bar has positive polarity,
Voltage change during restriking for positive surge voltage is 1pu
It is possible to suppress the generated voltage level of positive polarity switching surge voltage, which has been a problem in terms of insulation.

■Second Embodiment In this embodiment, the present invention is applied to a disconnector having an arc contact. That is, as shown in FIG. 4, an arc contact 12 is housed inside a shield electrode 11 connected to the power source side. Further, a shield electrode 13 is provided on the load bus bar side, and a movable electrode 14 is attached inside the shield electrode 13. Current switching is performed by the arc contact 12 and the movable electrode 14.

Further, in this case, the electric field strength on the arc contact 12 side is configured to be larger than the electric field strength on the movable electrode 14.

Also in the gas insulated switchgear of this embodiment having such a configuration, the residual voltage on the load bus side can be made positive as in the first embodiment.

*Other Examples* Note that the present invention is not limited to the above-mentioned embodiments, but can also be applied to the electrode film h1 of a circuit breaker, and the same effects can be obtained in that case as well.

[Effects of the Invention] As described above, according to the present invention, when connected to the power supply side,
In addition, by simply configuring the electric field strength on the electrode surface where an arc occurs to be greater than the electric field strength of the electrode connected to the load side, it is possible to eliminate metallic foreign objects that occur during the opening and closing operations of gas-insulated switchgear. 1- to the high voltage conductor of
It is possible to provide a gas-insulated switchgear that can prevent wrap and suppress the generation of positive surge voltage.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing a first embodiment in which the present invention is applied to a disconnector; FIG. 2 is a diagram showing the polarity and frequency of occurrence of residual voltage on the load side bus of a disconnector to which the present invention is applied; The figure shows the range of the opening speed and electrical asymmetry at which the residual voltage becomes positive, and FIG. 4 is a block diagram showing a second embodiment in which the present invention is applied to a disconnector having an arc contact. 1...Power supply side shield electrode, 2...Load side shield electrode, 3...Movable electrode, 6...! Metal container, 7...
Insulating gas, 8... Insulating spacer, 10... Power supply, 1
DESCRIPTION OF SYMBOLS 1... Power supply side shield electrode, 12... Arc contact, 13... Load side shield electrode, 14... Movable electrode.

Claims (1)

[Claims] In addition to filling an insulating gas inside a sealed metal container,
In a gas-insulated switchgear housing a disconnector or circuit breaker that has a switching section consisting of two opposing electrodes, the electric field strength on the surface of the electrode connected to the power supply side and where an arc occurs is the same as that of the electrode connected to the load side. A gas insulated switchgear characterized in that the electric field strength is greater than the electric field strength of the gas insulated switchgear.