Numerical Electromagnetic Field Analysis of Arc-Horn Voltages during a Back-Flashover on a 500 KV Twin-Circuit Line

Arc-horn voltages of a simulated 500 kV twin-circuit line in the case of one-phase back-flashover due to lightning to a tower top are analyzed by the thin-wire time-domain analysis (TWTDA) code. Prior to this analysis, a recently proposed flashover model is incorporated into TWTDA. It becomes clear that the arc-horn voltages of the other two phases show a quite similar time-varying characteristic alter one phase back-flashover. An EMTP simulation is also carried out. The archom voltages computed by EMTP agree well with those computed by TWTDA before the back-flashover on one phase. On the other hand, during about 1 μs after the one-phase back-flashover, the arc-horn voltages of the other two phases computed by EMTP deviate much from those computed by TWTDA. Particularly in the case of the middle-or the lower-phase back-flashover, the deviation is noticeable. The reason for this discrepancy is discussed.