Influence of lightning current waveforms of cloud-to-ground lightning with multi-return strokes on the lightning withstand level of 500 kV transmission lines

Abstract

The most common factor causing line tripping is lightning strokes, and it is necessary to conduct research on the lightning withstand level (LWL). The statistical results of lightning location systems (LLS) in various regions of China indicate that the total proportion of cloud-to-ground lightning with multi-return strokes in nature is 30% to 50%. The traditional method of lightning protection design for 500 kV lines based on the current waveform of single lightning strokes is no longer enough to effectively protect existing transmission lines. Therefore, in this paper an electromagnetic transient simulation model for 500 kV lines was established, to compare the LWL difference between single and multiple lightning strokes. The influence of the tower height, the grounding resistance, and the lightning current waveforms are all simulated and discussed. It is found that the back flashover LWL of 500 kV lines is significantly influenced by the lightning current waveforms. Meanwhile, reducing the grounding resistance cannot effectively increase the LWL of 500 kV lines when the tower is too high and the rise time of the lightning current is too short. It is proposed that the lightning current waveforms should be fully considered while calculating the LWL of 500 kV lines, both single and multiple lightning currents, providing a reference for practical engineering construction.