Study On The Lightning Protection Performance Of Shielding Failure For Inner Mongolia 500kv Transmission Line In Mountainous Area

With the rapid increase of power load, 500kV transmission grid has become the configuration in our country, double-circuit method has been an inevitable trend for 500kV trunk network. The advantage for higher voltage transmission is low power losses, but it also increases the incidence of trip-out caused by shielding failure, especially in the mountainous area in Inner Mongolia where shielding failure trip-out rate has even reached 70% of lightning outage rate. It has been found that the existing calculation model of shielding failure isn't consistent with the practical operation according to calculation methods of EHV, especially with high line tower. In Inner Mongolia, 500kV transmission lines are mainly located in mountainous and wild areas, whose shielding failure capability will be much significant to ensure the safe and stable operation of power system there.Many factors impose an effect on lightning performance of shielding failure of 500 kV double-circuit transmission lines in mountainous areas,in this paper , a research is done on the effect through EGM of double-circuit line. Calculation results show that shielding failure outage rate increases with the increase of overhead ground wire's protection angel , slope of ground surface , line height , wind yaw angel and decrease of striking distance factor and temperature . The tower structure of double circuit is very complicated,shielding failure outage rate will change if the tower structure changes, so we need calculate and analysis for different towers. The paper proposes an improved measure to prevent the lightning, there are: the lowering of overhead ground wire's protection angel, the installation of controllable lightning-conductor, using bypass shielding earthed wires, increasing insulation, choosing suitable line tower according to EGM and so on, what is especially to mention is that the paper also put forward some methods to reduce the shielding failure outage rate and the lightning trip-out faults, these methods include improve the coordination of lightning arrester and installation way.