Research On Lightning Protection For Secondary System In 500kV Qu Jiang Substation

Lightning protection research mainly focuses on primary equipment, the protection on secondary weak current equipment is lack of research. 500kV Qujiang substation in Shaoguan Guangdong is the pivotal substation of northern Guangdong grid, with the highest comprehensive automation level. 500kV Qujiang substation lies in area where lightning strike happens frequently, especially during thunderstorm season on May and June, lightining accidents occur frequently. Therefore, this thesis proposes research on lightning protection for secondary system in 500kV Qujiang substation.This thesis analyze and do field test on two lightning accidents happened in 500kV Qujiang substation in 2005 and 2006, find out path and reason of lightning overvoltage invasion: accident in 2005 is caused by lightning striking transmission lines, waves transferred from lines to low voltage cable; accident in 2006 is caused by lightning striking area nearby substation, low voltage lines brought about high amplitude introduced overvoltage, the low voltage surge protector relieve overvoltage to ground, however, since the earthing mode of equipotential copper cable is improper, earth potential is introduced to counterattack.In view of the two accidents, ATP simulation and experiment is done to research on surge voltage by lightning invasion low voltage power supply line and earthing mode of equipotential copper cable, effective measure to reduce lightning overvoltage invasion secondary system and correct multi-point earthing of equipotential copper cable is proposed. Conclusion is drawn that, based on simulation and experiment, according to principle that stick to comprehensive control, fortifying in each level, increasing accordingly, defense generally, comprehensive lightning protection for secondary system in substation is summarized, including power supply system, communication system and equipotential connection mode. Finally, practical and useful lightning protection transformation based on 500kV Qujiang substation is proposed, ensuring the safety and stable operation of 500kV Qujiang substation.