Evaluating the impact of power-frequency voltages on the indirect lightning performance of overhead distribution lines

This paper investigates the influence of power-frequency voltages on the indirect lightning performance of overhead distribution lines. Analyses on the subject often disregard this factor, assuming a de-energized line. However, in certain cases, e.g., when discriminating between single and multi-phases flashovers is of interest, the effect of the power-frequency voltage might be worth of investigation. The paper presents a comparative study of two methodologies implemented within the LIOV-EMTP simulation environment to account for the powerfrequency voltage effects. The first method employs a rigorous approach, incorporating voltage offsets in the Bergeron lines that interconnect LIOV and EMTP. The second method, though less precise, offers a simplified approach that has the advantage of avoiding modifications to the LIOV-EMTP interface used when the line is deenergized. A statistical analysis is conducted to quantify the effect of the power-frequency voltage on the predicted number of single and multi-phase flashovers and to evaluate the effectiveness of both methods in calculating the indirect lightning performance. By considering two lines characterized by different rated voltages, a sensitivity analysis is performed for different spacing between SAs and different values of both ground conductivity and SA grounding resistance.