What is the critical temperature and critical pressure of SF6 gas?- SF6在线监测系统_SF6检漏仪_SF6传感器_SF6密度继电器

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What is the critical temperature and critical pressure of SF6 gas?

发布时间：2020-01-13 来源：ydlcb 浏览次数：24次

From the basic physical characteristics of SF6 gas, it can be seen that it is relatively easy to liquefy gas compared with air. The state of SF6 gas depends on parameters such as its pressure and temperature.

The critical temperature is the highest temperature at which a gas can be liquefied. The lower the critical temperature, the less likely the gas is to be liquefied. The critical temperature of SF6 gas is 45.6 ° C, indicating that the temperature is higher than 45.6 ° C in order to maintain a constant gaseous state. At this temperature, as long as the pressure is high enough, it can be liquefied, (for example, 0℃ is about 1.2Mpa to begin liquefaction), but for N2 there is no liquefaction problem at room temperature, and it can be liquefied only after the temperature is lower than -146.8℃.

Factors affecting the strength of SF6 gas insulation

(1) Influence of electric field uniformity. Under a uniform electric field, the insulation strength increases linearly with the increase of the distance between contacts. When the distance is too large, the insulation strength increases and saturation occurs due to the uneven electric field. Under uneven electric field, its insulation strength will even approach the level of air.

(2) The relationship with pressure, under a more uniform electric field, the insulation strength increases with the increase of gas pressure, but it is affected by the thickness of the container wall and the volume of the internal components of the equipment. You can't raise the gas pressure too high. Generally, at 20℃, the pressure of SF6 gas chamber is 0.3-0.6mpa, and the pressure of SF6 arc extinguishing chamber is 0.5-0.7mpa.

(3) The influence of electrode surface state. Generally, the rougher the electrode surface, the lower the breakdown voltage. The larger the electrode area, the greater the probability of accidental factors, thus reducing the breakdown voltage.

(4) The influence of voltage polarity, because the insulation structure of the SF6 circuit breaker is a slightly uneven electric field form, its insulation level is often determined by the complex polarity voltage.