JPH0676703A - Vacuum circuit breaker - Google Patents

Abstract

PURPOSE:To maintain the mechanical strength of a vacuum circuit breaker, and improve its breakdown voltage so as to downsize the same by providing insulating frame openings in areas where electric field strengths are 70% or more of the maximum electric field strength of insulating barriers, in respective insulating frames of the insulating barriers. CONSTITUTION:Vacuum bulbs 1 are provided upper and lower with disk-like flanges 8a, 8b, and are sealed off as vacuum by insulating cylinders 9. Openings 10a, 10b are set in portions where central axes, combining the shortest insulating distances, cross insulating barriers 2 between the tips of the flanges 8a, 8b and barrier walls opposite to the tips of the flanges 8a, 8b, and are independently located in the upper and lower portions of the barriers 2 respectively, supporting and fixing the bulbs 1. The openings 10a, 10b are provided in approximately radial areas, opposite to the flanges 8a, 8b, where electric field strengths are 70% or more on the surfaces of the barriers 2, in the barriers 2 having insulating frames independently supporting the bulbs 1 for respective phases. Thereby, the increase of the electric fields is suppressed so as to improve breakdown, and the insulating distances are reduced so as to be capable of downsizing a vacuum circuit breaker without deteriorating mechanical strength.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum circuit breaker used, for example, in a gas insulated switchgear.

[0002]

2. Description of the Related Art Recently, a gas-insulated switchgear has been used in which electric devices such as a circuit breaker and a disconnector are collectively housed in a metal container and an insulating gas such as SF ₆ gas is hermetically sealed to reduce the size. Has been.

An example of the circuit breaker of this gas insulated switchgear is shown in FIG. In FIG. 4, the vacuum valves 1 in which the three phases are laterally arranged are fixed by insulating barriers 2 respectively to maintain insulation between the phases and the ground. As disclosed in Japanese Examined Patent Publication No. 3-13692, this structure fixes a vacuum valve 1 with a substantially coaxial cylindrical insulating barrier 2 having an opening on the front surface, a lead conductor 3 on the upper portion, and a lead conductor 3 on the lower portion. Are provided with similar lead conductors 4 and are respectively connected to electric devices (not shown). Although not shown, the lower lead conductor 4 is provided with a through hole at a substantially central portion, and a contact such as a multi-band is mounted in the through hole to move the conductor 5 up and down and to pull out the lead conductor 4. It has an electrical connection with. An insulating rod 6 is connected to the conductor 5 and is moved up and down by an operating force of an operating mechanism (not shown) to open or disconnect the electrodes of the vacuum valve 1. The insulating barriers 2 are fixed to the frame 7, respectively.

On the other hand, the vacuum valve 1 has a pair of electrodes, and in order to support the electrodes, the upper and lower disk-shaped flanges 8a and 8b are fitted to the cylinder of the vacuum valve 1, respectively.
There is a vacuum seal between the insulating cylinder 9 made of glass or the like.

For this reason, the insulation in the phase direction or in the ground direction of the board wall (not shown) is performed between the flanges 8a and 8b via the insulation barrier 2 and between the flanges 8a and 8 via the insulation barrier 2.
Between b and the board wall.

[0006]

However, between the flanges 8a and 8b via the insulating barrier 2 and between the flanges 8a and 8b.
Looking at the insulating structure between the board wall and the board wall, the relative dielectric constant of the enclosed insulating gas is about 1, while the insulating barrier 2 is made of an insulating material such as epoxy, so that the relative dielectric constant is as high as 4 to 5. Therefore, the electric field strength between the flanges 8a and 8b and between the flanges 8a and 8b and the board wall is increased by shortening the gas cap by the thickness of the insulating barrier 2. That is, the flanges 8a, 8b
Since the potentials of the spaces and the like are shared in inverse proportion to the relative permittivity, almost all the potentials are applied to the gas cap, and the electric field strength of the flanges 8a and 8b increases accordingly.

Generally, in the air insulation, the surface of the insulation barrier 2 is charged with electric charges having the same polarity as that of the flanges 8a and 8b, which has the effect of weakening the electric field strength of the flanges 8a and 8b and improving the withstand voltage characteristic. However, in an electrically negative gas such as SF ₆ gas in gas insulation, the breakdown voltage strongly depends on the electric field strength, so that the insulation barrier 2 is broken down before the load having the same polarity as the flanges 8a and 8b is charged. Will end up. This is considered to occur because the electron transfer in the gas is orders of magnitude faster than that in the air, and the insulating barrier 2 is not uniformly charged.

Therefore, the insulation barrier 2 can sufficiently exhibit the function of fixing the vacuum valve 1, but in terms of insulation, the insulation distance is equivalently shortened to lower the breakdown voltage. For this reason, it has been necessary to increase the interphase dimension and the insulation distance between the ground, which has been a factor in increasing the size. It is an object of the present invention to provide a vacuum circuit breaker that is miniaturized by maintaining mechanical strength and improving breakdown voltage.

[0009]

In order to achieve the above object, the present invention provides an insulating barrier having an insulating frame independent of each other, and a pair of electrodes which are fixed by being housed and fixed in the insulating frame of the insulating barrier. A vacuum valve that opens and closes the electric circuit with an insulating frame opening that is provided for a region of approximately 70% or more of the maximum electric field strength of the insulating barrier that is located facing the vacuum-sealed flange of the vacuum valve. The point is to have prepared.

[0010]

In such a structure, the electric field strength by the insulation barrier is provided by the insulation frame opening provided in the insulation frame independent of each phase of the insulation barrier in a region of approximately 70% or more of the maximum electric field strength of the insulation barrier. Can be prevented and the breakdown voltage can be improved.

[0011]

An embodiment according to the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing a breaking portion of a circuit breaker in which three phases are laterally arranged. In FIG. 1, the vacuum valves 1 are independent of each other and supported and fixed by an insulation barrier 2 to maintain insulation. The vacuum valve 1 has lead conductors 3 and 4 on the top and bottom.
Is connected to other electric equipment by providing a lead conductor 3 at the bottom.
A conductor 5 that can move up and down is pierced through. An insulating rod 6 is connected to the conductor 5, and the electrode in the vacuum valve 1 is shut off or turned on by an operating force of an operating mechanism (not shown). Further, the vacuum valve 1 has disk-shaped flanges 8a and 8b on the upper and lower sides, and the insulating cylinder 9 seals off the vacuum. The insulation barrier 2 supporting all of these is fixed to the frame 7 as in the conventional case.

Here, the insulating barrier 2 has a flange 8
Between the tips of a and 8b and between the board walls (not shown) where the tips of the flanges 8a and 8b face each other, openings 10a and 10b are provided at positions intersecting with the central axis connecting the shortest insulation distances.
The openings 10a and 10b are independently positioned above and below the insulating barrier 2 that supports and fixes the vacuum valve 1.

In these structures, the openings 10a, 10b
The relationship between the size of the electric field and the electric field strength of each part was investigated. FIG. 2 shows a model shape used for the analysis. Circular electrodes 11 simulating the flanges 8a and 8b are opposed to each other, and the insulating barrier 12 is formed between the electrodes 11.
Two sheets were inserted in -11 and the insulation barrier 2 of each phase was simulated. Further, the opening 13 of the insulating barrier 12 is provided symmetrically around the tip of the electrode 11-11, and the size of the opening 13 is W. In this model, the electrode 11 has a diameter of 116
mm, the distance between electrodes 11-11 is 34 mm, and the thickness of the insulation barrier 12 is 8 mm.
mm, the distance between the insulating barriers 12-12 is 2 mm, and the electrodes are equally spaced between the electrodes 11-11.

An example of this analysis is shown in FIG. The solid line A is the electric field strength curve on the surface of the insulating barrier 12, the dotted line B is the electric field strength curve at the tip of the electrode 11, and the alternate long and short dash line drawn parallel to the horizontal axis is the electric field strength without the insulating barrier 12. From this characteristic curve, it can be seen that when the size W of the opening 13 is increased, the electric field strength of the electrode 11 approaches a value without the insulating barrier 12. Further, it can be seen that the electric field strength on the surface of the insulating barrier 12 is about the same as the value without the insulating barrier 12 when W is 75 mm, and is lower when W = 75 mm or more. The electric field strength curves A and B are
The size W intersects at around 70 mm. The electric field strength at the intersecting point is 67% when the maximum electric field strength when the opening 13 of the insulating barrier 12 is not provided is 100%.
This is about 70% of the electric field strength distribution on the surface of the insulation barrier 12.
If the opening 13 is provided in a region having a ratio of not less than%, the electric field strengths of the electrode 11 and the insulating barrier 12 are about the same, and the optimum opening 13
Can be said to be the size of. If the opening 13 is made larger,
Although the electric field strength decreases and approaches the value without the insulation barrier 12, the mechanical strength of the insulation barrier 12 decreases. Opening 13
The size of must be determined in consideration of the mechanical strength.
Here, even in the analysis in which the ground between the electrode 11 and the flat plate is simulated, the number of the insulating barriers 12 is one, but the characteristics of the electric field strength are similar. That is, the openings 13 are provided independently on the two insulating barriers between the phases and one insulating barrier between the grounds so as to face the upper and lower flanges 8a and 8b.

By thus providing the opening 13 without significantly lowering the mechanical strength, the increase in the electric field strength due to the insertion of the insulating barrier 12 can be suppressed, so that the breakdown voltage can be improved. In particular, since the breakdown voltage strongly depends on the maximum electric field strength in SF ₆ gas, the effect is great, and the insulation distance between the phases and the ground can be shortened, whereby the entire vacuum circuit breaker can be downsized.

[0017]

As described above, according to the present invention, an insulating barrier having an insulating frame for independently supporting a vacuum valve for each phase,
By providing an opening in a substantially radial area where the electric field strength of the insulation barrier surface is about 70% or more, facing the flange that seals the vacuum of the vacuum valve, the electric field strength can be increased without lowering the mechanical strength. It is possible to obtain a vacuum circuit breaker capable of suppressing the breakdown voltage and improving the breakdown voltage, and at the same time reducing the insulation distance to make it compact.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view of a main part of a vacuum circuit breaker according to the present invention.

FIG. 2 is a diagram for explaining a vacuum circuit breaker of the present invention.

FIG. 3 is a diagram showing a relationship between an opening 13 of FIG. 2 and electric field strength.

FIG. 4 is an enlarged sectional view of a main part of a conventional vacuum circuit breaker.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Vacuum valve, 2 ... Insulation barrier, 8a, 8b ... Flange, 10a, 10b ... Opening

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuo Masaki No. 1 Toshiba-cho, Fuchu-shi, Tokyo Inside the Toshiba Fuchu factory (72) Inventor Kyofumi Nagata 1-1-1 Shibaura, Minato-ku, Tokyo Toshiba Corporation Head office (72) Inventor Keiji Waku 1-1-1 Shibaura, Minato-ku, Tokyo Toshiba Head Office

Claims (1)

[Claims] 1. An insulating barrier having an independent insulating frame for each phase, a vacuum valve housed and fixed in the insulating frame of the insulating barrier, and a vacuum valve for opening and closing an electric path by contact and separation of a pair of electrodes, and a vacuum valve of this vacuum valve. A vacuum circuit breaker, comprising: a vacuum-sealed flange; and an insulating frame opening provided in an area of approximately 70% or more of the maximum electric field strength of the insulating barrier located opposite to the flange.