Conducting particles in the compressed SF6 gas-insulated system can result in a loss of as much as 90% of dielectric strength and therefor constitute a serious threat to its safe and reliable operation. By the calculation of the electric field strength of the device

the auther evaluates that if there are linear conducting particles in the size ofφ#0.4mm× 3.0mm contaminating the 220kV or 110kV GIS of Baoshan Steel Works

in the case of havey overvoltage

a breakdown fault may occur under normal operating condition. Some preventing measures are proposed in the article.