JPH0137822B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to SF ₆ gas shield disconnectors, and in particular, to extinguish the arc in a short time by spraying SF ₆ gas onto the arc that occurs between a movable electrode and a fixed electrode during a large current disconnection. This invention relates to an SF ₆ gas shield and disconnector with an insulating nozzle located near the arc generating part to cause the arc to occur. [Prior Art] In this type of breaker, when the current is interrupted, a high-temperature plasma-like arc is generated between the movable electrode and the fixed electrode. In order to extinguish this arc, conventionally, an insulating nozzle made of fluororesin was used.
A stream of SF ₆ gas was being blown into the arc. but,
When an insulator made of fluororesin is exposed to a high-temperature plasma-like arc generated in high-pressure SF ₆ gas, the energy rays generated from the arc penetrate not only the surface of the nozzle but also the inside, creating voids and cracks inside the nozzle. It had the disadvantage of generating carbon and significantly reducing insulation performance. SF ₆ in Special Publication No. 53-28639 “Shiya disconnection”
Metal powder with a particle size of 3-20 microns, SiO ₂ , TiO ₂ , Al ₂ O ₃ , glass fiber,
A nozzle made of fluororesin to which 10-80% by volume of clay or talc is added is described. In addition, Japanese Patent Publication No. 48-38216 ``Tetrafluoroethylene-ethylene copolymer composition with high arc resistance'' describes a tetrafluoroethylene-ethylene copolymer composition.
One or more types of CaF ₂ , MgF ₂ , SbS, BaS, BN, 10
Compositions containing at least % by weight are described. In the above-mentioned known examples, it is not made clear how the nozzle in the SF ₆ gas chamber or disconnector functions in the SF ₆ gas. [Problems to be Solved by the Invention] The present invention provides a nozzle that is most suitable for an SF ₆ gas source or disconnector. An object of the present invention is to provide an SF ₆ gas shield breaker equipped with an insulating nozzle that prevents internal deterioration and surface wear due to arcing that occurs when a large current is interrupted. [Means for Solving the Problems] In order to achieve the above object, the present invention includes a fixed electrode, a movable electrode that approaches and separates from the fixed electrode, and a nozzle made of a fluororesin insulator that insulates between these electrodes. The nozzle sprays boron nitride powder onto the fluororesin insulator to extinguish the arc generated when the current is interrupted by spraying SF ₆ gas from the nozzle onto the arc generated between the electrodes. It is composed of an insulator that is contained as a filler and has a light reflectance of 60% or more at the melting point of the resin of the composition. Further, the present invention provides that at least the nozzle is made of a fluororesin insulator selected from a tetrafluoroethylene resin, a copolymer of tetrafluoroethylene and hexafluoropropylene, and a tetrafluoroethylene resin having a perfluoroalkoxy group. Contains boron nitride powder as a filler, and the light reflectance of the composition at the melting point of the resin of the composition is
This provides gas shields and disconnectors made of 60% or more insulating material. Furthermore, the present invention provides an insulator in which the nozzle contains 20% by volume or less of boron nitride powder as a filler in the fluororesin insulator, and the light reflectance of the composition at the melting point of the resin is 60% or more. We propose a gas shutoff switch consisting of: [Function] The present inventor focused on the characteristics of energy rays in the arc that occurs when a large current is interrupted, and as a result of intensive study on the nozzle, the nozzle was made of a fluorine-based resin containing boron nitride powder as a filler. It turns out that something consisting of objects is effective. It has also been found that the fluorine-based resin composition is particularly effective when the light reflectance is 60% or more at the melting point of the fluorine-based resin. In the present invention, particularly effective fluororesin insulators include tetrafluoroethylene resins, copolymers of tetrafluoroethylene and hexafluoropropylene, and tetrafluoroethylene resins having perfluoroalkoxy groups. Among these, experiments have revealed that tetrafluoroethylene resin in particular exhibits the best characteristics as a nozzle material for SF ₆ gas cylinders and disconnectors. The inorganic filler added to these fluororesin insulators is boron nitride (BN) powder. In the present invention, the insulator is made by adding these boron nitride powders to the fluororesin, and the amount added is such that the light reflectance of the insulator at the melting point of the resin is 60% or more. be adjusted. It is known that various inorganic fillers are added to fluorine-based resins, but boron nitride has a higher light reflectance over a wider wavelength range than other inorganic fillers, and as a result, the nozzle It has the advantage that it has a long lifespan because it does not absorb water. Here, the light reflectance at the melting point temperature of the resin is measured by making the resin itself into a gel state (transparent or optically transparent state) so that the reflectance of the resin itself is not taken into account. This is to measure light reflectance. Generally, the melting point of a fluororesin is also called the first transition point or gelling point, and is the temperature at which it loses crystallinity and becomes a gel. For example, in the case of tetrafluoroethylene resin, the melting point is 327°C, but for industrially molded resin, it is specified as 327±10°C by JIS standards. Even if the molded resin reaches a temperature above its melting point, it expands upon heating in the range of several tens of degrees Celsius, but its shape is almost maintained. In the present invention, the "melting point" is defined as a temperature that is equal to or higher than the upper limit defined in consideration of industrial variations and is close to the upper limit within a range where the shape and dimensions do not change significantly. In this state, the light reflectance of the fluororesin still has a value of several percent, but the influence of the filler dispersed in the resin on the light reflectance is small. In the comparative examples and examples described below, for example, the tetrafluoroethylene resin was measured at 340° C. in consideration of the above-mentioned JIS standard values. To measure light reflectance, filler-containing resin is made into a film, and the films are placed in parallel at a predetermined distance in a high-temperature chamber via a high-refractive-index transparent plate, and exposed to a certain light source at a predetermined distance. Wavelength (250nm
~800 nm) was irradiated, the film (sample) was totally reflected multiple times (n times) to determine the reflected light, and the reflectance was determined from the ratio of the incident light and the reflected light. I ₁ = (I ₀ − I ₂ ) η ⁿ lnI ₁ / I ₀ − I ₂ = nlnη, that is, reflectance η = (I ₁ / I ₀ − I ₂ ) ^1/n (I ₀ : light from the light source, I ₁ : Reflected light, I ₂ : Transmitted light when totally reflected on the same optical path only by the high refractive index transparent plate excluding the sample, I ₀ −I ₂ : Incident light) According to this method (multiple total reflection method) By making the thickness of the film large relative to the light wavelength λ, the effect of thickness on the reflectance can be sufficiently reduced. The light reflectance η obtained in this way is a function of the wavelength λ, and is called spectral reflectance and is expressed as η(λ). Since a light source generally has a spectral composition, incident light is also expressed as I ₀ (λ)−I ₂ (λ). In the present invention, when simply referring to reflectance, it refers to an average value obtained from the above spectral reflectance using the following formula. η＝∫η(λ){I ₀ (λ)−I ₂ (λ)}dλ／∫{I ₀ (
λ)-I ₂ (λ)}dλ In the present invention, the range of measuring the spectral reflectance and integrating and averaging the above equation is 250 nm to 800 nm,
It does not need to correspond to the spectrum of energy rays of the arc generated in the circuit breaker. A commercially available spectrophotometer can be used within this range. In the present invention, the amount of filler dispersed in the resin can be appropriately selected in order to make the light reflectance of the insulator 60% or more, but in addition to boron nitride powder, other fillers such as Powders such as alumina, titanium oxide, kaolin clay, zinc white, barium sulfate, and Bengara can also be dispersed in the resin. In the present invention, the amount of filler added is expressed in volume %. However, in actual preparation, since the resin and additives are in powder form, the addition ratio is determined by measuring their weight. Although this ratio is expressed in weight %, the volume % is significant since the present invention is aimed at the shielding effect of optical energy rays. Weight % and volume % are converted based on the specific gravity of the resin and additives. It is normal for this specific gravity to vary somewhat depending on the quality of the material, etc., and the generally accepted range from the lower limit to the upper limit must be considered here. [Example] Internal arc resistance was measured using an insulator prepared by adding various fillers shown in Table 1 to tetrafluoroethylene resin. In Table 1, the reflectance at 340°C was measured using the method described above, and does not refer to the value when the current is interrupted by an actual circuit breaker.

【table】

[Table] According to Table 1, 300kV in SF ₆ gas,
It can be seen that TiO ₂ and BN are superior in internal arc resistance of insulators after 10 cycles of 40 kA and after disconnection when the light reflectance is 60% or more. Even if 1% by volume of BN is added, if the molding conditions (temperature, pressure, filler quality - particle size, impurities, etc.) are not appropriate, the reflectance will be low and the ability to prevent arc light from entering will be low. Internal deterioration may also occur (see Comparative Example 11). Similarly, even if the amount of BN added is the same (see Practical Examples 3 and 4), the reflectance may differ depending on the molding conditions and the quality of the filler. The light reflectance of various filled fluororesins is shown in Figure 1 (reflectance of 0.8 in Figure 1 corresponds to approximately 60% light reflectance). BN-filled fluororesin is effective over a wide wavelength range. It can be seen that the spectral reflectance is over 60%. What is particularly noteworthy here is that the nozzle material doped with BN has a relatively flat and high spectral reflectance over a wide wavelength range. This means that the fluororesin composition containing BN has superior internal arc resistance compared to other cases. Table 2 shows the amount of nozzle wear when nozzle materials made from fluororesin compositions containing various fillers are exposed to an arc in the air, and the arc deterioration experiments were conducted by incorporating the nozzles into an actual SF ₆ gas circuit breaker. After doing so, the amount of consumption was determined. What can be said from the results in Table 2 is that if a nozzle material with a large amount of wear is used, the gap between the nozzle and the movable electrode will increase, which will lead to a _{corresponding} decrease in arc extinguishing ability. is not appropriate. Also, if we compare Table 1 and Table 2, TiO ₂ is
Like BN, it has excellent internal arc resistance, but the amount of wear, which means surface deterioration, is significantly greater than BN, so it is not effective as an insulator for SF ₆ gas or disconnectors.

〔Effect of the invention〕

As described above, according to the present invention, the insulating parts such as the insulating nozzle, which are exposed to the arc generated when large current is interrupted, have excellent durability. equipment can be provided.

[Brief explanation of drawings]

FIG. 1 is a graph showing the light reflectance of molded articles made of tetrafluoroethylene resin compositions containing various fillers.

Claims (1)

[Scope of Claims] 1. A device comprising a fixed electrode, a movable electrode that comes into contact with and separates from the fixed electrode, and a nozzle made of a fluororesin insulator provided between these electrodes. The arc that occurs between the electrodes
In the arc breaker which extinguishes the arc by spraying SF ₆ gas, the nozzle contains boron nitride powder as a filler in the fluororesin insulator, and the light reflectance of the composition at the melting point of the resin of the composition is An SF ₆ gas disconnector characterized by being made of an insulator that is 60% or more. 2. The fluororesin insulator is a fluororesin insulator selected from a tetrafluoroethylene resin, a copolymer of tetrafluoroethylene and hexafluoropropylene, and a tetrafluoroethylene resin having a perfluoroalkoxy group. According to claim 1, which is characterized in that:
SF ₆ gas breaker. 3. The SF ₆ gas shield disconnector according to claim 1, wherein the fluororesin insulator is a tetrafluoroethylene resin. 4. The SF ₆ gas shield disconnector according to claim 1, wherein the nozzle contains 20% by volume or less of boron nitride powder as a filler in the fluororesin insulator. 5. The SF ₆ gas shield disconnector according to claim 1, wherein the nozzle is made of a composition containing 20% by volume or less of boron nitride powder as a filler in tetrafluoroethylene resin.