Effect of high-resistivity ground on the lightning performance of overhead lines

This paper presents an approximate formula for the peak-value of the lightning overvoltages induced on aerial lines installed over high resistivity ground, which is valid up to 10 kΩ m. The formula is validated by comparing its results with results obtained from more accurate techniques. The formula is then applied in a Monte Carlo code to assess the effect of high-resistivity ground on the lightning performance of distribution lines without grounded neutral conductor. The results show that, for good conducting ground (e.g., 100 Ω m), indirect flashes are relevant for the 100 kV CFO lines, but they are not relevant for the 170 kV CFO lines. For poorly-conducting ground (e.g., 1000 Ω m), indirect flashes are relevant for 170 kV CFO lines, but they are not relevant for the 300 kV CFO lines. Indirect flashes become relevant for the 300 kV CFO lines only for very poor-conducting ground (e.g., above 2000 Ω m). The paper results also show that using a grounded neutral conductor improves significantly the indirect lightning performance of distribution lines.