Abstract
In order to improve the reliability of the power supply, it is necessary to prevent the lightning faults of transmission line and substation apparatus. However, the faults are caused occasionally in lower voltage power system, particularly in 77kV level. The governing factor for insulation strength of substation apparatus is lightning impulse voltage, and it is necessary to know the voltage level and distribution in a substation caused by lightning surges, in order to investigate the rational insulation coordination. For this purpose, authors have measured lightning surges at two 77kV conventional type substations from 1990 to 1993. In this paper, the characteristics of induced lightning surges and back flashover lightning surges are described. The comparison of the related surge voltages at two substations, the power line phases at grounding fault and the equivalent capacitance of substation are also discussed.
