Abstract & Overview
Although ice-melting flashover of insulator strings has become one of the important problems which have a severe impact on the safe operation of transmission lines,the analysis of ice-melting flashover for ice-covered parallel insulator strings is rarely to see.This paper study on the impact factors of ice-melting flashover based on two times of ice-melting flashover obstacles in field for ice-covered long insulator string of 500 kV transmission line.The influence of crystallization effect on the redistribution of conductive ions during the freezing water transition from liquid to solid phase is discussed.The impact of parallel arrangement,units and structured with alternately large and small diameter sheds on the ice-melting flashover gradient of insulator strings is analyzed.The base value of AC ice-melting flashover voltage gradient of 500 kV transmission line is determined as 65 kV/m.To type I and type II suspension insulator strings of 500 kV transmission line,the countermeasures such as change the arrangement mode of insulators and reform the tower head to prevent ice-melting flashover are proposed.