Estimation of the Critical Lightning Currents Causing Flashover to Overhead Transmission Lines through Iterative ATP-EMTP Simulations by Means of an External Program

The critical lightning currents (minimum values) causing flashover of overhead transmission line insulation are required for computing the line lightning flashover rate, LFR. The latter comprises the shielding failure flashover rate, SFFOR, and backflashover rate, BFR. Hence, two critical currents associated with the lightning performance of the lines are defined: the minimum shielding failure flashover current and the minimum backflashover current. These currents can be calculated employing simplified analytical methods. More accurate estimates can be obtained via electromagnetic transient simulations performed iteratively, using detailed simulation models for fast-front transients. This work deals with the estimation of line critical currents through ATP-EMTP simulations by means of an external program developed in MATLAB, facilitating parametric investigations. An application to 150 kV double-circuit lines is presented considering tower height and insulator length as parameters.