Investigation Of Typical Lightning Stroke Obstacles On 500kV A.C. And D.C. Transmission Lines

Eight typical lightning stroke obstacles on 500kV Tianshengqiao-Guangzhou(refer to T-G line below for short) A.C. and D.C. transmission lines are introduced which happened in Bose city of Guangxi Province in 2004 year. The reasons of the obstacles and the protection against lightning of 500kV A.C. and D.C. transmission lines are analyzed and discussed. The calculating results and analysis show that the lightning stroke faults are caused by the shielding failure ,at the same time, it also proves that the back-stroke trip-out rate is enough few but the shielding failure trip-out rate is very many and the shielding failure has become main lightning stroke faults for the 500kV T-G A.C. and D.C. transmission lines. The 500kV T-G A.C. and D.C. transmission lines were designed according to the standards of nation, these standards were revised from the 220kV-330kV designing standards of the Soviet Union and the operational experience of the northern HVAC in China. Back-stroke is main and shielding failure is secondary in the standards ,but actually the shielding failure is main factor with regard to the mountainous 500kV T-G A.C. and D.C. transmission lines. Because the design does not fit the actuality, so the lightning-protection level is not perfect. The paper presents the measures for decreasing lightning stroke trip-out to aim directly at the shielding failure of 500kV T-G A.C. and D.C. transmission lines in Bose city. It will help in making the correct lightning-protection judgment for the China Southern Power Grid especially power supply from west to east.