Tower-footing resistance and lightning trip-outs of 150 kV transmission lines in west sumatra in Indonesia

Abstract

The trip-out rates calculated by taking account of the reduction in the tower-footing resistance due to the ionizing effect agree well with the observed ones. This indicates the importance of the impulse resistance in the analysis of the lightning performance of the line. The trip-out rate at the lower arm is high for the cases of the average grounding resistance of 33.3 ohms, and the rates at the upper arm are high for the cases of the average grounding resistance of 5.6 ohms. Such à trend can be simulated by the IEEE method using the impulse resistance. The trend for the trip-out ratio to become high with the increase in the span length is significant after improvement of the tower-footing resistance. However, the trend is weak before improvement of the tower-footing resistance. This is because in the case of the high tower-footing resistance the flashover occurs before the arrival of the wave reflected from the adjacent towers due to the high potential rise of the tower. Therefore, the degree of the influence of the span length on the trip-out ratio is dependent on the tower-footing resistance. The local lightning activity significantly affects the trip-out rate.