Estimation of Lightning Overvoltages and Critical Currents Causing Flashover to a 150 kV Overhead Transmission Line: Effects of Recorded Lightning Current Waveforms

This work evaluates the influence of typical first return-stroke current waveforms of negative downward lightning flashes, as recorded in literature, on the computed fast-front overvoltages on a typical 150 kV overhead transmission line. The critical flashover currents are also assessed. The investigation is performed through ATP-EMTP simulations considering lightning strikes to towers (backflashover) and phase conductors (shielding failure). Results for recorded lightning current waveforms are compared with those obtained for the widely used CIGRE waveform; the front time, maximum steepness, and time to half value of the latter are varied according to their statistical distributions. A comparison between CIGRE and double-peak waveforms is also performed. It is shown that the use of actual recorded return-stroke current waveforms may affect considerably the computed overvoltages and critical currents. The leader development models employed for flashover prediction are discussed in terms of the criterion used to terminate leader propagation for withstand cases.