JPS61190910A - Gas insulated transformer - Google Patents

Abstract

PURPOSE:To further improve the lightening-proof characteristics of the title transformer by a method wherein a gapless arrester, connected to the line side end of a transformer coil, is built-in in sealed gas. CONSTITUTION:A gapless arrester 8 is housed in a tank 1 together with transformer coils 4 and 5, an iron core 6 and a tap changer 7, and inert gas 9 such as sulfur hexafluoride (SF6) and the like having the dielectric strength higher than air is sealed as an insulating medium in the inner space which is airtightly sealed by the tank 1 and a cover 2. A zinc oxide (ZnO) and the like, having very small current to flow at the rated voltage or below is used as a characteristic element and a series gap is abbreviated on the gapless arrester 8. As a result, the lightening surge entered from outside into the transformer passing through a high-tension bushing 3 is absorbed by the gapless arrester 8 on the midway, it is discharged to the ground, and the lightening surge is prevented from entering into the transformer coil 4, thereby enabling to protect the transformer coils 4 and 5 from the lightening surge.

Description

[Detailed description of the invention] [Field of application of the invention] The present invention relates to a lightning-resistant gas insulated transformer.

[Background of the invention]

Gas-insulated transformers were developed with the aim of making transformers nonflammable, and are particularly suitable for outdoor use, and based on their track record, their use in distribution transformers such as pole-mounted transformers is also being considered. However, conventional gas-insulated transformers filled with SF8 gas have inferior lightning resistance compared to oil-filled transformers, so when applied to pole-mounted transformers, it is necessary to further improve the lightning resistance.

In order to improve the lightning resistance characteristics of gas-insulated transformers, arresters have traditionally been connected to cables or overhead wires outside the transformer. They lacked response characteristics to surges, and sometimes did not provide sufficient protection.

Conventionally, as a transformer with a built-in arrester, there was a transformer with a built-in arrester in a Yujinbashira 4-top transformer (Jikko Sho 5l-456).
11) is known, but since the arrester is installed in the transformer oil, if an accident such as an explosion of the arrester occurs, there is a risk that the insulating oil will catch fire and cause a fire accident. , not suitable for practical use.

[Purpose of the invention]

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

[Summary of the invention]

The present invention provides a gas insulated transformer in which an inert gas having a higher dielectric strength than air is filled as an insulating medium.
It is characterized by a built-in arrester.

[Embodiments of the invention]

Figure 1 shows an embodiment of the present invention. (a) is an internal structure diagram, and (b) is a wiring diagram. A gapless arrester 8 is housed in a tank 1 along with a transformer coil 4.5, an iron core 6, and a tap changer 7. The sealed internal space is filled with an inert gas 9 such as sulfur hexafluoride (st'a) having a higher dielectric strength than air as an insulating medium. The transformer coils 4% 5 are each connected to an external line via a high voltage bushing 3 and a low voltage bushing 10, and a gapless arrester 8 is connected between the line side end of the high voltage coil 4 and the ground.

Gapless arrester 8 uses a zinc oxide (ZnO) element as a characteristic element, which has extremely low follow-on current below the rated voltage, and omits the series gap. This is because the lightning surge is absorbed by the gapless arrester 8 on the way and discharged to the ground.

The lightning surge is prevented from entering the transformer coil 4, and the transformer coil 4.5 can be protected from the lightning surge.

FIG. 2 shows another embodiment of the present invention applied to a three-phase transformer, and the reference numerals are the same as in FIG. 1.

〔Effect of the invention〕

According to the present invention, since a gapless arrester is built into the gas sealed in the gas insulated transformer, the lightning resistance characteristics of the gas insulated transformer can be significantly improved compared to the conventional art.

In other words, by installing the arrester inside the transformer close to the transformer coil to be protected, the coupling impedance between the arrester and the coil is reduced, so the original characteristics of the arrester are fully utilized, and the arrester is protected against particularly steep surges. It is possible to significantly improve the response characteristics to the current, and eliminate the problem of breakdown of insulation coordination due to arrester discharge current.

On the other hand, by using a gapless arrester as the built-in arrester, it is possible to maintain stable lightning resistance characteristics without being affected by changes in the internal pressure inside the sealed transformer, unlike ordinary geared arresters. I can do it.

In addition, the characteristics of gapless arresters deteriorate due to contamination and suction, so if they are installed externally, they must be enclosed in a sealed container made of porcelain or the like. In this case, since the gapless arrester is placed in a clean sealed gas, the gapless arrester does not deteriorate in characteristics due to contamination or suction even in the open type, and is highly reliable and economical.

Furthermore, unlike oil-immersed transformers, gas-insulated transformers are nonflammable, so even if the built-in arrester explodes, there is no risk of fire, and when applied to pole-mounted transformers, safety But there's no problem.

[Brief explanation of drawings]

FIGS. 1(a) and (b) Fi are structural diagrams and wiring diagrams showing one embodiment of the present invention, and FIG. 2 is a wiring diagram showing another embodiment of the invention. 4.5; Transformer coil; 8: Gapless arrester;
9: Inert gas. 1st side C (1) $ 2 Figure

Claims (1)

[Claims] A gas insulated transformer filled with an inert gas having a higher dielectric strength than air as an insulating medium, characterized in that a gapless arrester connected to the line side end of the transformer coil is built into the filled gas. vessel.