Incorporating the LEMP Impact on Lightning Surge Analysis of Transmission Lines in EMT Simulators

Abstract

Electromagnetic transient (EMT) analysis is an important tool to estimate the lightning performance of transmission lines. In this paper, we advanced the EMT analysis method for transmission lines by incorporating the lightning electromagnetic pulse (LEMP) impact. Analyses by the proposed method clarify the mechanism of the LEMP impact on lightning overvoltages of transmission lines: the LEMP induces voltages having a polarity opposite to those generated by the lightning current, and these LEMP-induced voltages increase the insulator voltages; the EMT analysis without considering the LEMP impact provides lower insulator voltages for both struck and nearby towers. The models used in the proposed method can be synthesized immediately and straightforwardly from the geometries of the towers and lines, and the analysis can be performed within a short time. Moreover, various transmission lines-500, 275, and 77 kV class vertical double-circuit lines and a 275 kV class horizontal single-circuit line-were studied assuming a ground resistivity ranging from 0 to 5000 m, and all the results were validated by the three-dimensional finite-difference timedomain method for solving Maxwell's equations. Thus, the proposed method is a powerful tool and has a potential impact on the lightning performance assessment of transmission lines and insulation coordination studies.