Tower Air‐gaps discharge characteristics and insulation coordination for UHV AC double‐circuit line

Abstract

In order to give out inverse V-type insulator tower air-gaps configuration of double-circuit UHV AC power transmission line, different distance air-gaps from high-voltage electrode to tower frame discharge tests of inverse V-string are carried out. Discharge characteristics curves of power frequency voltage, 1000 μs long wave-front switching impulse voltage, and lightning impulse of UHV AC double-circuit tower are obtained. Results show that the 50% discharge voltage gradient of bottom phase air-gaps is higher than middle phase. 1000 μs wave-front switching impulse 50% discharge voltage gradient of bottom phase air-gaps is 4.6% higher than the middle phase. Based on the test results and the characters of operating voltage and overvoltage of UHV AC power transmission system, the UHV AC double-circuit tower inverse V-type insulator air-gaps configuration is proposed. The air-gap configurations of power frequency voltage and switching overvoltage are 2.9 and 6.5 m, and the lightning protection air-gaps are 6.7 and 7.2 m, in mountains and plains.