Study On AC Pollution Flashover Characteristics Of Porcelain Long Rod Insulator

Porcelain long rod insulator is one type of transmission line insulator which has special structure.It has the advantages of good self-cleaning and mechanical performance.Porcelain long rod insulator is widely used in Jiangsu,Hubei and other places of 220kV,500kV AC lines and ±500kV DC lines and the application amount in Jiangsu is the most.Pollution flashover is the issue which power system need to defend.Pollution flashover accidents of porcelain long rod insulator appeared in recent years.Accidents involved Yihua line in Hubei,Guoshan line and Tiandu line in Jiangsu and seriously endangered the safety of power grid.The study on contamination and pollution flashover characteristics of porcelain long rod insulator at home and abroad now is less.The study of contamination is mainly for the performance after long-term contamination and doesn't eliminate the impact of self-cleaning.The study also lacks the further test of AC pollution flashover characteristics.Therefore,this paper studies contamination and pollution flashover characteristics of porcelain long rod insulator systematically and puts forward anti-pollution measures to guide the anti-pollution work and state maintenance of porcelain long rod insulator.This paper studied the contamination characteristics of porcelain long rod insulator through contamination sampling,natural contamination test,wind tunnel artificial contamination test and contamination simulation model.Results show that when the rainfall is low,the contamination rate of porcelain long rod insulator is greater than disk type porcelain insulator.In heavy polluted and little rainy area,the contamination rate of porcelain long rod insulator is about 3.35 times of disk type porcelain insulator in a month.When there is no rain for a long time,porcelain long rod insulator should be cleaned in time before bad weather.This paper studied the AC pollution flashover characteristics of porcelain long rod insulator through AC artificial pollution tests.Results show that the utilization ratio of creepage distance of porcelain long rod insulator is less than disk type porcelain insulator.Uneven contaminants of top and bottom surface will increase the pollution flashover voltage of porcelain long rod insulator while windward and lee side will reduce.The increase proportion is 4.2%to 54.7%while the reduce proportion is 3.2%to 9.5%.The pollution flashover voltage of porcelain long rod insulator increases with the reduce of NaCl and increase of CaSO4 in contaminants.This paper put forward the anti-pollution measures of coating RTV and adding creepage extender and studied the influence of anti-pollution measures on contamination and pollution flashover of porcelain long rod insulator through contamination and pollution flashover tests.Results show that coating RTV and adding creepage extender can increase the pollution flashover voltage of porcelain long rod insulator effectively.The pollution flashover voltage of porcelain long rod insulator will increase 67.9%to 91.8%after coating RTV and 27.2%to 53.1%after adding creepage extender.However these two anti-pollution measures will influence global or local contamination of porcelain long rod insulator at the same time.In heavy polluted and little rainy area,spraying RTV to mandrel of porcelain long rod insulator,in emergency circumstances,adding one creepage extender to the middle or two creepage extenders to single porcelain long rod insulator.Porcelain long rod insulator is not recommended to be used in heavy polluted and little rainy area.