JPH01142452A - Sf6 decomposition gas sensor for high voltage ac load switch - Google Patents

Abstract

PURPOSE:To diagnose the inferiority of the switching operation of a contact or the losing effect of an adsorbent and to prevent an accident, by forming an SF6 decomposition gas sensor for a high voltage AC load switch from an epoxy resin molded product filled with a silicon-containing inorg. powder. CONSTITUTION:This sensor 1 is constituted by providing silver paste electrodes 3 to both surfaces of a disc-shape epoxy resin molded product filled with a silicon-containing inorg. powder whose surface resistance is gradually lowered by the long-time exposure to SF6 decomposition gas and leading out lead wires 4 from the electrodes 3. The surface insulating resistance of the disc is gradually lowered in such a state that the end surface of the disc is exposed to the SF6 decomposition gas and this insulating resistance is measured by applying DC high voltage between the electrodes 3. By this method, the inferiority of the switching operation of a contact or the losing effect of an adsorbent is diagnosed and an accident is prevented.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an 8F decomposition gas sensor disposed in a container of a high-pressure AC load switch (hereinafter referred to as a gas switch) in which SFa scum is sealed as an arc-extinguishing medium. Regarding.

(Prior technology) Conventionally, substation K [SFa gas insulated switchgear (G
As a type of insulation diagnosis method for IS), a sensor has been developed that chemically detects the concentration of decomposed gas generated by partial discharge in SFg gas.

These sensors use a thin film of alumina photo film polymer or polyacetylene whose resistance value suddenly changes when it comes into contact with SFg decomposition gas. This sensor is effective when the 8Fs decomposed gas concentration is relatively low (below 0.1 pPm) and gradually increases with the duration of the partial discharge, as in the case of GIS.

However, in a gas switch, there are switching contacts and senna and S in the container.
It also contains an adsorbent for Fs decomposition gas. The arc discharge caused by the opening and closing of the contacts generates a large amount of decomposed gas, and the decomposed gas concentration in the container temporarily decreases [100 to 1100].
0 pI). This decomposed gas is gradually adsorbed by the adsorbent, and the decomposed gas concentration approaches equilibrium, but the thin-film sensor described above works when the concentration reaches a high level and becomes unusable after that. .

:'/X Role of SFg decomposition gas sensor in switch 11
J is to detect that the decomposed gas generated by the 7-way discharge when the contacts are opened and closed is gradually less likely to be adsorbed by the adsorbent, and that the decomposed gas concentration at equilibrium gradually increases. If the arc time becomes longer due to poor opening/closing operation, or if the number of opening/closing operations increases, the total amount of decomposed gas generated also increases. On the other hand, if the adsorbent has expired or its amount is insufficient, it will take a long time for the internal cracked gas concentration to reach equilibrium, and the equilibrium concentration will also become high. This would lead to abnormally high wear and tear on the switch contacts and deterioration of the insulators, shortening the lifespan of the nine devices.

Therefore, as an 8F6 decomposition gas station for gas switches,
It is not necessary to refer to the instantaneous decomposed gas concentration, but it is preferable to correspond to the cumulative concentration over time. Note that in GIS, internal gas is sampled and the concentration of decomposed gas is detected using a gas detection tube or a gas chromatograph. However, this method mainly measures the concentration of decomposed gas at equilibrium, and it is inefficient to collect gas from each of the many gas switches placed on pillars or underground. It is.

(Problems to be Solved by the Invention) The present invention solves the problem of cracked gas concentration (t, b) which is relatively unresponsive to the instantaneous cracked gas concentration and which changes over the course of one hour (t, b) which increases when opening and closing. Equilibrium though.

As the number of years of operation increases, the time it takes to reach equilibrium becomes longer and the equilibrium concentration also becomes higher.Insulation resistance gradually changes in response to the accumulation of 0 hours. This provides a new sensor. By tracking changes in the insulation resistance of this sensor along with the number of years of operation, it is possible to detect abnormalities in one device (contact abnormalities and adsorbent abnormalities), and it is also possible to estimate the remaining life of normal devices.

(Means for Solving the Problems) The present invention relates to an SFa decomposition gas sensor for a gas switch using an epoxy resin molded product filled with inorganic powder containing silicon. Electrodes are attached to two locations on this surface, and the insulation resistance between the electrodes is measured.

In the present invention, the silicon-containing inorganic powder is used at a volume ratio of 40 to 60 with respect to the epoxy resin molded product in terms of dispersibility in the mixture of the inorganic powder, viscosity of the mixture, and void-free molded product. It is preferable to use

FIG. 1 is a cross-sectional view showing one example of the structure of the decomposed gas sensor of the present invention. The sensor 1 has silver paste electrodes 3 on both sides of a disc of an epoxy resin molded product 2 filled with an inorganic powder containing silicon whose surface resistance gradually decreases when exposed to SF'a decomposition gas for a long time.

A lead wire 4 is drawn out from this electrode.

9 while the end face of the disk was exposed to SFg decomposition gas.
The surface insulation resistance gradually decreases, and this is measured by applying a DC high voltage between the electrodes 3.

The shape of the epoxy resin molded product filled with inorganic powder containing silicon does not have to be a disk, and may be a rectangular parallelepiped. The electrodes may be made of silver paste, conductive paint, metal vapor deposition, or metal foil pasted with adhesive.

2 to 4 show a sensor having a shape showing another embodiment of the present invention, FIGS. 2 and 3 are sectional views, and FIG. 4 is a plan view. FIG. 2 shows the above-mentioned epoxy resin molded product 2 with a metal electrode 8 integrally molded therein. FIG. 3 shows the above-mentioned epoxy resin molded product 2 molded around a metal rod 8 and an electrode 3 coated on the outer periphery. FIG. 4 shows electrodes 3a and 3b coated on the epoxy resin molded product 2 described above.

In FIGS. 2 to 4, 4 is a lead wire.

Due to the arc that occurs when opening and closing the contacts of a gas switch,
8Fg gas is first decomposed as follows.

Srg-→SFa+2F Next, 8F4 reacts with the trace amount of remaining moisture.

SFn+H20→5OFz+ 2 HF5OFz+H2
0→80g+2HF HF' (hydrogen fluoride) thus generated is very likely to react with Si. For example, it reacts violently with silica (SiOz).

SiO+4HF-→2 HzO+ SiF4HF
Because of its small molecular size, it easily penetrates into plastics. Then, where Si is present, Si9 reacts and Si
produces gn. SiF4 is a gas with a boiling point of -86℃, so 9
The plastic coating on the surface ruptures, creating a hole. Si
F4 further reacts with trace amounts of HF' and moisture.

SiF4+2HF+H Snow 0→HzSiFs+HzOThis Hz8iFs has strong electrolytic properties and significantly reduces the surface resistance. When the surface resistance of an insulating part to which a high voltage is applied decreases locally, local electric field concentration occurs and creepage breakdown occurs.

Therefore, insulating parts used in SFg gas insulated equipment are generally epoxy resin molded products filled with powder such as alumina, which is not susceptible to HF', instead of silica. Glass fibers also contain Sit, and for glass fiber reinforced epoxy resin molded products (GFRP), should corrosion-resistant paint be applied to the surface?

Alternatively, a layer of organic fiber base material is provided on the surface.

The thickness of the corrosion-resistant layer is 0.5 mm to avoid penetration of HP.
3- or higher. Also, avoid using silicone rubber containing Si for the O-ring of the airtight gasket.

Generally neoprene/rubber is used.

To evaluate the SFm decomposition gas resistance of the material, - Observe the change in surface resistance over time of the membrane material in an HF gas atmosphere. In the past, decomposed gas was generated by discharging in SFa gas and placed in the atmosphere, but it has since been found that the pressure can be sufficiently simulated even in the atmosphere of HF gas.

FIG. 5 shows the equipment used for measurement in the examples of the present invention, which is placed at the bottom of a container 5 made of polytetrafluoroethylene.

Pour 301HF aqueous solution 7 and place sample sensor 1 in the upper space.
was left hanging from the drawer terminal 6. Then, it was left at room temperature, and after a predetermined date, a DC voltage of 1000 V was applied between the terminals, and the insulation resistance was measured after 1 minute.

In the present invention, an epoxy resin molded article filled with inorganic powder containing silicon is used as a solid insulating material whose surface resistance decreases when exposed to 8F's decomposition gas for a long time.

Silica, silicon carbide, talc, glass powder, etc. are used as the inorganic powder containing silicon. If the surface resistance decreases in a short time due to exposure to SF or decomposition gas, a thin layer of synthetic resin lacquer may be applied to the surface of the molded product to delay the penetration of HF gas. As the material, the above-mentioned silicon-containing inorganic powder may be mixed with a silicon-free inorganic powder such as alumina, water-containing alumina, zircon, dolomite, and aluminum oxide.

(Example) Examples will be described below. The shape of the sensor is as shown in Fig. 1, and an epoxy resin-based silver paste "Epinal EN-40804 (manufactured by Hitachi Chemical Co., Ltd.) is applied to the side plane of a filled epoxy molded product 2 with a diameter of 20 mm and a thickness of 10 mm.
was applied and cured at 130° C. for 1 hour to obtain electrode 3. As the lead wire 4, a polytetrafluoroethylene coated copper wire was used.

For the epoxy molded product containing filler, 100 parts by weight of Epikote 828 (manufactured by Shell) and HN-
2200 (Epoxy resin curing agent manufactured by Hitachi Chemical Co., Ltd.) 80
parts by weight and 0.5 parts by weight of N,N-dimethylbenzylamine were used. The type of filler and its filling amount (volume % relative to the molded product) are shown in the table below.

A comparative example was filled with alumina powder that was not affected by SF6 decomposition gas. Example 1 was filled with silica powder. Example 2
was filled with half alumina powder and half silica powder. Example 4
．． 5.6 were filled with silicon carbide, glass powder, and talcum powder, respectively. In Example 3, the sensor shown in Figure 1 was constructed using the molded product of Example 1, and then an acrylic lacquer "Tuffy TF-1141J (manufactured by Hitachi Chemical Co., Ltd.) was sprayed and air-dried to form a coating with a thickness of 10 μm. A film was formed.

FIGS. 6 and 7 are graphs showing changes in insulation resistance over time measured by the method described above. In the comparative sensor shown in FIG. 6, which is filled with alumina powder, the insulation resistance hardly decreases even if it is left in HF gas, so it is not suitable as a sensor. The sensor of Example 1 filled with silica powder can be said to have good sensitivity, with insulation resistance reduced by six orders of magnitude. On the other hand, because the sensitivity is too high, there is a possibility that considerable deterioration may occur in a state where the concentration of SFm decomposed gas is high during opening and closing.

The senna of Example 2, which was filled with a 50/50 mixture of silica powder and alumina powder, had lower sensitivity than the sensor of Example 1, but the decrease in insulation resistance tended to reach saturation at about 4 digits. It will be done. In the sensor of Example 3, in which a coating film (thickness: 10 μm) of acrylic lacquer was applied to the sensor of Example 1, the insulation resistance decreased almost uniformly with the number of days left.

Excellent sensor function. Further, the reduction in insulation resistance will eventually reach six orders of magnitude as in Example 1.

If the synthetic resin coating film is too thin, it will be similar to Example 1.

On the other hand, if it is too thick, the sensitivity will deteriorate, so the thickness should be 5 to 20.
It is preferable to set it in the range of ttm.

The sensors of Examples 4 to 6 shown in FIG. 7 are also Example 1 #1.
Although there is no decrease (6 digits), it can be said that it can be used satisfactorily as an SFg decomposition gas sensor.

(Effects of the invention) The SF"s decomposed gas sensor of the present invention includes epoxy resin,
This sensor utilizes the phenomenon that the surface resistance of an epoxy resin molded product filled with silicon-containing powder gradually decreases when exposed to SFg decomposition gas for a long time.

This sensor is placed inside the gas switch and external changes in insulation resistance can be checked over time.

It can diagnose defects in contact opening/closing operation and failure of adsorbent.

It is possible to prevent accidents.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one example of the configuration of a decomposed gas sensor of the present invention, FIGS. 2 and 3 are sectional views of a sensor showing other embodiments of the present invention, and FIG. 4 is a plan view, FIG. 5 is a sectional view of a sensor function evaluation device. FIGS. 6 and 7 are graphs showing changes in insulation resistance of the sensor over time. Explanation of symbols 1...Sensor 2...Epoxy resin molded product 3...Silver paste electrode 4...Lead wire 5...
・Container 6...Output terminal 7...HF
Aqueous solution 8... Number of metal electrodes released (Y) Kudzu 6 Figure

Claims (1)

[Claims] 1. SF_6 decomposed gas sensor for high-pressure AC load switch using an epoxy resin molded product filled with inorganic powder containing silicon. 3. The SF_6 decomposed gas sensor for a high-pressure AC load switch according to claim 1, wherein a synthetic resin coating film is applied to a thickness of 5 to 20 μm on the surface of an epoxy resin molded product filled with inorganic powder containing silicon.