Lightning Performance of Quadruple-circuit Transmission Line with Dual Voltage 1000 kV/500 kV on the Same Tower

Mixed-voltage multi-circuit transmission line on the same tower can be considered in UHV grid in eastern area where line corridor is tensional.Aiming at the problem whether there are any different characteristics in lightning performance between UHV mixed-voltage multi-circuit transmission lines on the same tower and conventional transmission lines,back flashover and shielding failure trip-out rate of quadruple-circuit transmission line with dual voltage 1000 kV/500 kV on the same tower were calculated with PSCAD/EMTDC and improved EGM.Moreover,the influences of distance H between bottom cross arm of 1000 kV and top cross arm of 500 kV,protection angle θs,and width l of top cross arm of 500 kV line,on shielding failure lightning performance was analyzed.Furthermore,the lightning performance of quadruple-circuit transmission line with dual voltage 1000 kV/500 kV on the same tower and other voltage level mixed-voltage transmission line on the same tower were compared.The results show that back flashover trip-out rate of line is lower,but there is the possibility of double-circuit back flashover trip-out of 500 kV line.Shielding failure trip-out rate of line is higher than that of other voltage level mixed-voltage transmission line;with θs and H increasing,shielding failure trip-out rate of 1000 kV line(n21) becomes larger,and n21 decreases with l increasing.Shielding failure trip-out rate of 500 kV line(n22) is unaffected by θs,n22 decreases first then increase with H increasing and n22 increases with l increasing.The integral shielding failure trip-out rate of transmission line increases with θs,H and l increasing.In order to reduce the shielding failure trip-out rate of transmission line,θs and H can be reduced and l can be increased appropriately in range of 19.06~25.06 m.