Why does sulfur hexafluoride circuit breaker have good arc extinguishing performance?- SF6在线监测系统_SF6检漏仪_SF6传感器_SF6密度继电器

韦弗斯新闻动态

最新动态

SF6安全保障专家

专注于SF6气体检测的专业化

135 85763546

Why does sulfur hexafluoride circuit breaker have good arc extinguishing performance?

发布时间：2017-10-12 来源：ydlcb 浏览次数：38次

Sulfur hexafluoride gas has excellent insulation and arc extinguishing properties, and is called "century gas". Its emergence has caused a very far-reaching innovation in high voltage switchgear. Because sulfur hexafluoride gas has excellent insulation and arc extinguishing performance, it is widely used in today's transmission and distribution switchgear above 110kv and 24kv~36kv generator protection circuit breakers. In the distribution switchgear above 35kv, the electrical industry departments in some large cities and regions should use sulfur hexafluoride circuit breakers to replace other circuit breakers. The development and application of sulfur hexafluoride gas insulated switch combination electrical equipment with miniaturization, lightweight, less (free) maintenance and intelligence in 3.6kv~27.5kv distribution switchgear is becoming more and more extensive. As far as the world market is concerned, Europe and most Middle Eastern countries are biased towards SF6 switches.

The reason why sulfur hexafluoride has a strong arc extinguishing ability is mainly because:

one Sulfur hexafluoride gas forms a plasma composed of sulfur, fluorine atoms, positive and negative ions and electrons at high temperature, and the plasma has a high temperature at the arc temperature, so the same current, the arc voltage is low, the heat generated in the arc gap is less, and the smaller arc blowing speed can make the arc get enough cooling.

2. The temperature characteristics of the conductivity and specific heat capacity of sulfur hexafluoride are relatively special. When the arc temperature reaches a certain value, the heat absorption effect becomes larger, and the thermal conductivity also increases, which has a strong cooling effect on the arc, so the arc becomes finer in sulfur hexafluoride. Because the arc column is thin and contains less heat, the dielectric recovery rate of the arc gap rises faster, so the sulfur hexafluoride switch device can withstand a high recovery voltage rise rate.

3. Sulfur hexafluoride is very electronegative. Sulfur hexafluoride molecules are easy to capture free electrons and form negative ions. The mobility of heavy negative ions is low, which makes the development of electron collapse difficult, thus weakening the development process of discharge and improving the rising speed of medium recovery.

4. SF6 gas is rapidly decomposed into F and S single atoms when the arc temperature reaches 2000-3000K, and a large amount of heat energy is absorbed from the arc during decomposition, that is, it has "high thermal conductivity", so SF6 gas has excellent arc extinguishing performance.

Sulfur hexafluoride (SF6) has good electronegativity, and its molecules can quickly capture freedom and form negative ions. The conduction effect of these negative ions is very slow, which accelerates the recovery rate of the arc gap medium strength, so it has a good arc extinguishing performance. At atmospheric pressure, the arc extinguishing performance of sulfur hexafluoride is one hundred times that of air, and does not deteriorate after arc extinguishing, and can be reused.

SF6 molecule has strong electronegativity, which makes SF6 have strong arc extinguishing ability. Because SF6 molecules become negative ions after adsorption of free electrons, negative ions are easy to combine with positive ions to form neutral molecules, so that the electrical conductivity of the arc space quickly disappears. Especially when the arc current is close to zero, this effect is more significant. If SF6 gas is used to blow the arc, a large number of fresh SF6 molecules are constantly in contact with the arc, and the arc is extinguished more rapidly. Due to the strong arc extinguishing ability of SF6 gas, the change rate from conductive arc to insulator is particularly fast, so the breaking current of SF6 circuit breaker is large, and the breaking time is short. Under the same voltage level, the same breaking current and other conditions are the same,SF6 circuit breakers have fewer series breaks.

What are the consequences of sulfur hexafluoride circuit breaker temperature too low

The main effect of sulfur hexafluoride circuit breaker temperature is too low under a certain pressure, after sulfur hexafluoride liquefaction, the actual pressure of the circuit breaker is reduced, according to the KPA curve, the insulation distance is not enough, resulting in the switch can not work normally. Sulfur hexafluoride circuit breaker uses sulfur hexafluoride density relay to monitor gas pressure changes; Sulfur hexafluoride is a very good noble gas, which has an antioxidant effect on the contacts of components and is large in being.

Under what circumstances sulfur hexafluoride circuit breaker gas pressure is very low 0.35 in the morning, high at noon.

This phenomenon occurs when the ambient temperature is very cold and the daily temperature difference is relatively large. This is because sulfur hexafluoride gas will be liquefied when it is below minus 30 degrees Celsius. After the gas is liquefied, its volume is greatly reduced, so the internal pressure is also greatly reduced. By noon, when the temperature rises above the sulfur hexafluoride gas gasification temperature, the original pressure will be restored. Generally, sulfur hexafluoride circuit breakers operating in this environment will explain the situation to the manufacturer when ordering, and the manufacturer will configure the heater to heat the gas at extremely low temperatures so that it is not liquefied. Sulfur hexafluoride gas is also mixed with carbon dioxide gas in foreign countries to reduce the liquefaction point of the gas.