Impact of Mains-Frequency Voltage on Lightning Induced Overvoltages in Surge Protected Lines

In studies analyzing the indirect lightning performance of overhead lines, the steady-state voltages at mains frequency are usually neglected, assuming that the line is not energized. However, in certain cases, e.g., when the occurrence of flashovers on one phase or on multiple phases is of interest, neglecting the steady-state voltage effect might be inadequate. This paper compares two methods to account for the steady-state voltage effect by using the LIOV-EMTP software. The first is an accurate approach that includes voltage offset in the Bergeron lines connecting LIOV and EMTP. The second is an approximate method that does not require any change in the LIOV-EMTP interface but is based on a modified representation of network components implemented in EMTP. A statistical analysis is carried out to compare the effectiveness of the two approaches.