Method of calculating shielding failure flashover times of transmission line in complex terrain area

Calculating shielding failure flashover rate of transmission line with regulation method, EGM method and LPM method, the height of conductor and ground wire are often expressed by average height, the terrain feature are often expressed by ground obliquity. If the actual line parameters are beyond the scope of the effective calculation conditions, traditional methods can't reflect the influence of sag and line corridor's complex terrain area. In recent years, some scholars put forward to select multiple tangent planes of a line span, then calculated the shielding failure flashover rates of every tangent planes to reflect the line span's lightning protection performance, but it was complicated to get the ground obliquities of every tangent planes. A new approach for calculating shielding failure flashover times in complex terrain area was presented, which was based on the electro-geometric model (EGM), the new method considered of the line corridor's micro-topography and the relative position among the ground wire, the conductor wire and the ground, a line span was taken as the research object, got the shielding failure flashover times of the line span through calculating the conductor exposed surface's horizontally-projected area. A 500kV transmission line in complex terrain area was taken as an example, the calculation results shown that using this method can obtain a line span's lightning protection performance simple and exactly, and reflect the influence of line corridor's complex terrain area better, which also provide a reference for differentiation technology and strategy of lightning protection.