Estimation of Sparkover Rate of Medium-Voltage Line Due to Indirect Lightning Hit Taking Account of Correlation between Peak Value and Front Duration of Return-Stroke Current Waveform

Abstract

The lightning-induced voltage has been one of the factors for the insulation design of a power distribution line. The authors have developed a method of analysis of induced voltages where the Agrawal's model is adopted as a field-to-line coupling model. In this paper, the sparkover rate of a medium-voltage line associated with indirect hits is investigated based on numerical calculations and statistical analysis by taking account of the correlation between the peak value and the front duration of the return-stroke current waveform. Regardless of the intensity of the correlation between these parameters, the sparkover rate associated with a subsequent stroke is higher than that associated with a first stroke when the line is equipped with surge arresters. Furthermore, it is shown that the sparkover rate significantly decreases with the increase of the correlation coefficient. This demonstrates the importance of the study of the correlation between the return-stroke current parameters.