JPS6029201B2 - gear press lightning arrester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gapless lightning selector using a metal oxide voltage nonlinear resistor element.

Conventional lightning arresters use a series gap and a voltage nonlinear resistor element mainly composed of silicon carbide, and house them in an atmosphere of gas (dry air, nitrogen, etc.) that makes it easy to control the discharge starting voltage of the series gap. was.

However, recently developed earth arresters using voltage non-linear resistor elements of metal oxides only allow a current of about a few Amps to flow even when the rated voltage is applied, so a series gap is unnecessary and the dry This is a gearless lightning arrester that houses only a metal oxide voltage nonlinear resistor element in an insulating tube or insulating tube in an air or nitrogen gas atmosphere.

However, in particular, a so-called mini-clad gas insulated switchgear, in which a gapless earth arrester containing a voltage non-linear resistor element of metal oxide is housed in an insulating tube filled with dry air or nitrogen gas, is housed in a metal tank filled with SF6 gas. When used as a gapless arrester, the only internal element of the arrester is a voltage nonlinear resistor, so its effective length is much shorter than that of a conventional arrester.

This has the advantage that the lightning arrester itself can be made smaller and lighter, but it also has the disadvantage that the insulation distance inside the lightning arrester cannot be maintained. The gapless lightning arrester for mini-clads uses SF6 gas to insulate the outside of the snow arrester, so it is possible to maintain a sufficient insulation distance from the outside surface, but there is no SF inside the snow arrester.
If the surge arrester is filled with SF6 gas, decomposition gas of SF6 gas will be generated, considering the case where the pressure protection membrane is activated due to the increase in internal pressure when the surge arrester follows or fails to shut off.
SF6 gas cannot be used, so the gas is separated using an insulating tube and filled with dry air or nitrogen gas. However, SF6
Compared to the case in gas, the insulation distance is required to be about 5 times, and there is a disadvantage that there is a lack of a reliable resistor. The present invention is basically to improve the insulation inside the surge arrester in a gapless current arrester in which the outside is insulated with SF6 gas and the inside with dry air or nitrogen gas, and to obtain a gapless lightning selector that is small and has excellent insulation characteristics. With the goal.

An embodiment of the present invention will be described based on FIG.

As shown in FIG. 1, in a surge arrester main body 5 which is gas-divided by an insulating tube 4 etc. housed in a metal tank 2 via an SF6 gas 3, a voltage non-linear resistor made of metal oxide is used as an internal element 6. It is constructed by stacking a required number of elements 7.

Dry air or nitrogen gas 8 is sealed in the insulating cylinder 4, and SF6 gas or Freon gas is mixed therein as will be described in detail later, thereby constructing the gapless lightning arrester 1 suitable for mini-cladding. In this case, the structure of the arrester main body 5 takes up the necessary height and the space necessary for the knee protection structure when the internal element 6, which is composed of stacked voltage nonlinear resistor elements 7 made of metal oxide, is fixed with springs 10, etc. The size is as follows.

By insulating the earth arrester main body 5 from the SF6 gas 3 with the insulating spacer 9, a compact gapless earth arrester can be provided. Note that reference numeral 13 indicates an insulating rod that is provided around the inner element 6 and supports the element 6. On the other hand, the lightning arrester main body 5
One side protrudes from the metal tank 2 and is located outside, and a bran preventer 11 is attached to this outer end and grounded. The other side is connected to a conduit busbar conductor (not shown) via a conductor 90 provided on the spacer 9. The gas sealed in the lightning arrester main body 5 is dry air or nitrogen gas mixed with SF6 gas or Freon gas.

By mixing SF6 gas into nitrogen gas, the dielectric strength of the atmosphere can be increased. For this reason, the internal atmosphere of the snow protector body 5 is dry air or nitrogen gas 8.
By mixing SF6 gas therein, it becomes possible to compensate for the insufficient insulation distance inside the lightning arrester main body 5. In the case of a gapless earth arrester using a metal oxide voltage nonlinear resistor element 7, there is no discharge phenomenon, so the gas in the atmosphere in which the element 7 is accommodated may be a gas that improves the insulation distance. good.

Considering this point, SF6 gas is optimal. Considering only this point, it would be possible to simply accommodate the internal element 6 of the earth arrester in the metal tank 2 filled with SF6 gas 3, eliminating the need for the insulating cylinder 4, or there would be problems in terms of explosion-proof construction. Therefore, in the present invention, the gas is separated from the metal tank 2 by an insulating tube 4, etc., and the internal atmosphere of the earth arrester body 5 is made mainly of dry air or nitrogen gas 8, and the inside of the insulation tube 4 and the inside of the earth arrester are SF6 gas is filled in to compensate for the insufficient insulation distance of element 6 to obtain the required dielectric strength. In this way, since most of the atmospheric gas inside the arrester is dry air or nitrogen gas, even if the explosion protection device 11 operates when the arrester fails to conduct current or fails to shut off, the adverse effects of the decomposition gas of SF6 gas can be prevented. can be kept to a minimum.

Since the height of the insulating tube 4 can be minimized, it is possible to reduce the size of the insulating cylinder 4. Here, it is better to reduce the amount of SF6 gas mixed into the atmosphere inside the arrester as much as possible, since the decomposed gas, HF, S
02, S2F2, SF2, SF4, S2F, o, SOF
2. The generation of toxic gases such as S02F2 gas can be suppressed as much as possible.

The amount of these decomposed gases generated depends on the arc current, time, SF
Although it cannot be determined quantitatively as it depends on the density and amount of the 6 gas, the presence of just a few ppm of this decomposed gas is harmful, so it is better to have as little SF6 gas mixed into the dry air or N2 gas as possible. The improvement in dielectric strength when SF6 gas is mixed into dry air or N2 gas varies depending on the gas pressure, type of applied voltage, gap length, etc., but it is important to note that the improvement in dielectric strength when SF6 gas is mixed in dry air or N2 gas varies depending on the gas pressure, type of applied voltage, gap length, etc. If so, it is almost comparable to the dielectric strength of 100% SF6 gas. In addition, the smaller the volumetric mixing ratio of SF6 gas, the greater the improvement in dielectric strength. Therefore, the ratio of SF6 gas infiltration should be kept at a maximum of 50% or less in terms of volumetric mixing ratio, and SF6 gas should be mixed at a lower ratio than that. This compensates for the lack of internal space within the earth arrester main body 5.

The effect appears when it is present in a volumetric mixing ratio of 1% or more. Note that the internal atmosphere of the mini-clad gapless surge arrester 1 to which the present invention is applied uses a voltage nonlinear resistor element 7 made of metal oxide, so its volume is small, and even if a maximum of 50% SF6 gas is mixed in. However, the amount is small. Further, since the effective length of the earth arrester internal element 6 can be expected to have a considerable dielectric strength, there is no need to increase the pressure of the mixed gas so much, and the required dielectric strength can be expected to be sufficient at approximately atmospheric pressure. Therefore, the amount of SF6 gas is small, and the decomposed gas when the lightning protection device 11 of the lightning arrester operates does not reach a level where it would have an adverse effect. FIG. 2 shows another embodiment of the invention. As shown in the figure, this embodiment, in which the same parts as those in FIG. A gapless lightning arrester 14 is constructed by accommodating an earth arrester internal element 6 consisting of an oxide voltage nonlinear resistor element 7. In this case, the height of the effective Nagara 0chi insulator 12 of the lightning arrester 14 is the height when the internal elements 6 are stacked, and the relationship is that only the metal oxide voltage nonlinear resistor element 7 is used without using a gap. Since the insulating rod 13 providing the metal oxide voltage non-linear resistor element 7 may be short in insulation distance if determined by the characteristics of the insulator tube itself such as the leakage distance of the insulator tube 12, the insulating distance may be insufficient. In this case as well, to obtain the required dielectric strength,
Since SF6 gas is mixed in the dry air or nitrogen gas 8 in the atmosphere inside the insulator tube 12, the required dielectric strength can be obtained as in the case of the mini-clad gapless lightning arrester 1 shown in FIG. Furthermore, in the above configuration, even when the explosion-proof device 11 is operated in the event of current arrestor failure or disconnection, the amount of SF6 gas is small, so the influence of the decomposed gas is very small. Further, instead of the SF6 gas to be mixed in, Freon gas, which has a lower dielectric strength but similar characteristics, can also be used. As described above, the present invention has a gapless earth arrester configuration in which a voltage non-linear resistor element of metal oxide filled with SF6 or Freon gas, which has a higher dielectric strength, is housed in a dry air or nitrogen gas atmosphere. Therefore, while the effective length of conventional lightning arresters was determined by the height when the internal elements were loaded, the effective length can now be determined by the electrical characteristics of the outer surface of the vessel, making it suitable for mini-cladding. Especially in the case of electric shock absorbers, they can be made smaller and lighter.

Furthermore, it is possible to provide a gapless lightning arrester that is not affected by decomposition gas even when the explosion protection device is activated.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an embodiment of a mini-clad gapless earth arrester to which the present invention is applied, and FIG. 2 is a cross-sectional view of an embodiment of the gapless snow arrester containing a ceramic pipe to which the present invention is applied. 1...Gapless lightning arrester, 2...Metal tank,
3...SF6 gas, 4...Insulating tube, 5
...Earth protector body, 6...Earth protector internal elements, 7...Metal oxide voltage nonlinear resistor element, 8...Dry air or Nitrogen gas, 11...
...Image prevention device, 12...Insulator tube, 13...
... Insulating rod, 14 ... Gapless lightning arrester with insulator tube. Figure 2 Figure 1

Claims (1)

[Claims] 1. An internal element formed by stacking voltage nonlinear resistor elements of metal oxides, a container containing this internal element, a first insulating gas sealed in the container, and a first insulating gas containing the container and containing a first insulating gas inside the container. and a tank filled with SF_6 gas as the second insulating gas, and the first insulating gas is a mixed gas of dry air or nitrogen gas mixed with SF_6 gas or Freon gas, and the SF_6 gas or Freon gas is the dry air or 1% to 50% by volume mixing ratio in nitrogen gas
Gears press lightning arrester characterized by containing %.