Study on applicable conditions of transmission line tower foundation natural grounding in less thunderstorm days region in Northwest China

Tower grounding of transmission line is one of the most important measure to maintain the normal operation of power system and to guarantee the security of personnel. There is no need to lay artificial grounding when the natural grounding follows the regulators. In some northwest district of China whose number of thunder is few, ground flash density and lightning trip-out rate is low and therefore the counter trip-out rate is less, especially for high pressure transmission line. If the current standard is adopted in these areas, the term is too harsh to implement with economic benefit. So, it is significant to propose a new grounding standard to be applied in northwest district of China. In this paper, we modeled the tower and its grounding body of transmission line by the electromagnetic method. Then we calculated the counter trip-out rate under the condition of natural grounding and proposed the standard of natural grounding for 750kV transmission line in less thunder region.