Abstract
In recent years, improvements in the reliability and quality of the power supply are more desired than ever before. However, the fault caused by lightning ranks still first in the power system below 154 kV, therefore effective prevention of the lightning faults is needed. 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 surge, in order to investigate the rational insulation coordination. For this purpose, authors have been measuring lightning surges at two 77 kV conventional type substations since 1990. In this paper, the automatic measuring systems for lightning surges invading into substations are reported, and measuring results are analized statistically.
