JPH0719708B2 - Gas insulated pole transformer - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a lightning protection type gas insulated transformer.

[Background of the Invention]

The gas-insulated transformer was developed with the aim of making the transformer non-flammable, and is particularly suitable for outdoor use. From its track record, it is also being considered for use in distribution transformers such as pole transformers. However, the conventional gas-insulated transformer filled with SF ₆ gas is inferior to the oil-filled transformer in lightning resistance, so it is necessary to further improve the lightning resistance when applied to pole pole transformers.

To improve the lightning resistance of gas-insulated transformers, an arrester has been conventionally connected to the cable or overhead line outside the transformer.However, because the coupling impedance between the arrester and the transformer coil is relatively large, there is a sharp lightning strike. In some cases, the response characteristics to the sirsi were lacking, and sufficient protection could not be achieved.

Conventionally, as a transformer with a built-in arrester, it is known that an oil-filled pole transformer has a built-in arrester (Actual Publication No. 51-45611), but this is because the arrester is installed in the transformer oil. In the unlikely event that an arrester explodes, the insulating oil may catch fire and cause a fire accident, which is not suitable for practical use.

[Object of the Invention]

An object of the present invention is to provide a highly reliable and safe gas-insulated pole transformer with further improved lightning resistance.

[Outline of Invention]

The present invention relates to a tank having an opening at the top, a cover for hermetically closing the opening, a transformer main body having a low voltage coil and a high voltage coil and an iron core arranged at the bottom of the tank, and a high voltage coil fixed to the cover. High-voltage bushings electrically connected to the high-voltage coil, a gapless arrester with one end connected between the line-side end of the high-voltage coil and the high-voltage bushing, and the other end grounded. A gas-insulated pole-mounted transformer with an insulating medium made of a highly inert gas, in which a gapless arrester is held in the tank in a substantially horizontal direction between the transformer body and the cover, and one end of the transformer is kept inside the tank. Is arranged so as to face each other in the substantially central portion and the other end is grounded near the inner wall of the tank.

Example of Invention

FIG. 1 shows an embodiment of the present invention. (A) is an internal structure diagram and (b) is a connection diagram. The transformer coils 4, 5, the iron core 6, the tap changer 7, and the gear press / arrestor 8 are shown.
Is contained in the tank 1, and an inert gas 9 such as sulfur hexafluoride (SF ₆ ) having a higher dielectric strength than air is filled as an insulating medium in the internal space sealed by the tank 1 and the cover 2. . Transformer coils 4, 5 are high voltage bushings 3,
It is connected to an external line via a low voltage bushing 10, and a cap press arrester 8 is connected between the line side end of the high voltage coil 4 and the ground.

The gear press / arrestor 8 uses a zinc oxide (ZnO) element or the like, which has a very small follow current at a rated voltage or less, as a characteristic element and omits the series gear tap, and enters the inside of the transformer from the outside through the high voltage bushing 3. The lightning surge is absorbed by the gear press arrester 8 on the way and discharged to the ground, so that the lightning surge is prevented from entering the transformer coil 4 and the transformer coils 4 and 5 can be protected from the lightning surge.

FIG. 2 shows another embodiment of the present invention applied to a three-phase transformer, and reference numerals are the same as those in FIG.

〔The invention's effect〕

According to the present invention, it is possible to obtain a gas-insulated pole transformer having excellent lightning resistance, high reliability, and high safety.

That is, since the arrester is held in the tank in a substantially horizontal direction between the transformer body and the cover, the arrester can be installed inside the transformer in a position close to the transformer coil to be protected. Since the coupling impedance between and becomes small, the original characteristics of the arrester can be fully utilized, the response characteristics especially to a steep surge can be greatly improved, and the problem that the insulation coordination is broken by the arrester discharge current is eliminated. Further, since the arrester is held in a substantially horizontal direction in the tank so that one ends thereof face each other at substantially the center of the tank and the other end is grounded in the vicinity of the inner wall of the tank, currents in opposite directions to each other are applied to the arrester. Even if it flows, the generation of electromagnetic repulsive force between arresters is prevented, damage to the arrester or its mounting portion can be prevented, and safety and reliability are improved.

On the other hand, by using a gear press or arrester as the built-in arrester, it is possible to maintain stable lightning resistance characteristics without being affected by the change in internal pressure in a transformer that is sealed like a normal arrester with a gear trap. .

In addition, since the characteristics of the gear press and arrester deteriorate due to contamination and moisture absorption, it is necessary to enclose it in a hermetically sealed container such as a magnet when externally mounted. If it is contained, it is placed in a clean filled gas, so that the gear pressless arrester is highly reliable and economical even if it is an open type, without causing damages or deterioration of characteristics due to moisture absorption. In particular, since the arrester is held in the tank in a substantially horizontal direction between the transformer body and the cover, it will be arranged substantially horizontally in the high temperature part in the tank.
The whole is heated almost evenly and a large effect of preventing moisture absorption is obtained.

Furthermore, since the insulating medium consisting of an inert gas is non-flammable unlike the insulating oil of oil-filled transformers, there is no risk of fire if the built-in arrester should explode, so it is applicable to pole transformers, etc. In this case, there is no problem in terms of safety. Since the inert gas is used as the insulating medium and the arrester is built in the tank, the transformer can be made smaller and lighter, and it is easy to handle during installation and safety is improved.

[Brief description of drawings]

1 (a) and 1 (b) are a structural diagram and a connection diagram showing an embodiment of the present invention, and FIG. 2 is a connection diagram showing another embodiment of the present invention. 4, 5: Transformer coil, 8: Gears press arrestor, 9: Inert gas.

Claims (1)

[Claims] 1. A tank having an opening above, a cover for hermetically closing the opening, a transformer main body having a low-voltage coil and a high-voltage coil and an iron core arranged at the bottom of the tank, and fixed to the cover. A plurality of high-voltage bushings electrically connected to the high-voltage coil, a gapless arrester having one end connected between the line side end of the high-voltage coil and the high-voltage bushing and the other end grounded, in the tank The gapless arrester is held in the tank in a substantially horizontal direction between the transformer body and the cover, and the one end of the gapless arrester is provided in the tank in a substantially horizontal direction. A gas-insulated pole transformer, wherein the gas-insulated pole transformer is arranged so as to face each other in a substantially central portion of the tank and to be grounded at the other end near an inner wall of the tank.