Advantages and disadvantages of SF6 gas
SF6 gas has excellent insulation performance. Its electrical resistance is 2.5 times that of air, and its arc extinguishing performance is 100 times that of air. Its electrical resistance at 0.294Mpa is close to that of transformer oil. There is no carbon element in SF6 gas, so the structure of the equipment is relatively free in design.
SF6 electrical equipment maintenance cycle is long, easy to maintain, occupy the ground and small space volume. The fully closed combination electric appliance made of SF6 gas as insulation medium can include circuit breaker, isolation switch, ground switch, mutual inductor, bus, lightning arrester and other components. And the high voltage live part is completely sealed in the steel shell, no electric shock hazard, improve the safety of operation. At the same time, due to closed combination, to avoid the external environment (such as industrial pollution, high altitude, frost thundersnow climate), suitable for large cities, industrial intensive areas, steep mountain terrain, serious pollution areas of the substation installation and use.
The disadvantage of SF6 gas, although it is non-toxic, but its severe, not easy to dilute and diffusion, is a kind of asphyxiating substance, in fault leakage is easy to cause staff oxygen, poisoning and asphyxia.
When SF6 gas generates corona discharge in an electric field, SOF2 (sulfonyl fluoride), SO2F2 (sulfonyl fluoride), S2F10 (disulfide decafluoride), SO2 (sulfur dioxide), S2F2 (sulfur fluoride), HF (hydrofluoric acid) and other nearly ten gases will be decomposed. These fluoride and sulfide gases are not only toxic, S2F10 is extremely toxic, and many are corrosive. Such as aluminum alloy, porcelain insulator, glass epoxy resin and other insulating materials, can damage their structure; It has strong stimulating and toxic effects on human body and respiratory system. These shortcomings of SF6 gas constitute the main problems in safety protection of SF6 electrical equipment.