Study On±800kV DC Flashover Characteristics Of Glass Insulator In High Altitude Area

With the development of electric power system in China, outdoor insulation is becoming more and more important in the construction of±800kV Ultra High Voltage DC transmission line. The different distribution of resource and power consumption made it inevitable for the transmission line to be constructed in high altitude area. In high altitude, both the air pressure and the atmosphere density are smaller than those in plain area, resulting in a smaller flashover voltage. The glass insulator, although has been widely used for its advantage in arc resistance and faulty insulator explosion, has not been deeply studied under DC voltage. Therefore, it is of great importance to study the flashover characteristics and the leakage current of glass insulator under DC voltage in high altitude area.Also, the DC flashover characteristics of glass insulators under different ESDD, NSDD and uneven contamination patterns were studied in practiced high altitude area (2100m). The test results indicate that the arc levitation phenomena are much more serious in high altitude area. Thus the creepage distance is not the only important factor of flashover characteristics.Based on these tests, the leakage current signals are also recorded and analyzed in this paper. The eigenvalues of leakage current, such as amplitude and quantity are chosen and analyzed as the key features of leakage current.The results show that the flashover characteristics for glass insulators are similar to those for porcelain insulators. Experimental results indicate that ESDD(equivalent salt deposit density), NSDD (non soluble deposit density) and uneven contamination patterns have a significant effect on t he flashover characteristics of glass insulator. Leakage current pulse amplitude was divided into three stages with the time change. under uniform stained manner, the relationship between Im/U50%and salt density approximation grows in linear. The leakage current increases with the degree of pollution of surface increases at uneven contamination patterns.