The Influence Of Environmental Temperature Change On The Performance Of SF6 Current Transformer And Countermeasures

Current transformer (CT) is important interconnecting element of primary and secondary system in power system, the early CT is most oil-immersed current transformer which mostly has the disadvantages that inside humidity is more and uneasy to shed, transformer oil is liable to deteriorate with regular change and inconvenient transportation, etc.With excellent performance of insulation and arc extinction, SF6 used as insulating medium can effectively avoid the shortcomings of oil-immersed current transformer, so SF6 becomes the premier selection of insulating medium for 110 kV and above voltage class. SF6 CT has more significant advantages in the electrical performance, electromagnetic performance, thermal performance and mechanical performance than that of oil-immersed current transformer, and the operation is safe and reliable, the service life is long and the maintenance is simple. When SF6 gas has a certain water content, the discharge happened inside, SF6 gas decomposition will appear a series of chemical reaction with water content, which may produce HF leading to metallic material corrosion; on the other hand when ambient temperature drops, micro-water may condense on the surface of insulating material, caused the sudden drops of creeping flashover voltage, so which may result in accident of power system. As the research background of 330 kV CT explosion in Eastern Yinchuan of Ningxia power grid, the paper presents the ideaThat sudden variation of ambient temperature is the cause of porcelain bushing explosion. Firstly, ambient temperature is closely connected with micro water content in SF6. Secondly, during the operation, the upper and below position in CT exist larger temperature difference, making water content transfers in CT, which may lead to partial condensation dew occur in sudden variation of ambient temperature, as a result caused CT faults. Based on the above thoughts the author does deeply research about the influence of ambient temperature’s sudden variation on the operation performance of SF6. CT, and puts forward some corresponding countermeasures.