STUDY ON ELECTRICAL STRENGTH OF SUSPENSION INSULATORS IN STEEP IMPULSE VOLTAGE RANGE

High and steep lightning surge voltages sometimes cause electrical pun ctures of suspension insulators. Microscopic analysis clarifies electr ical breakdown mechanism of ceramic material. V-t characteristics of t he insulators are closely examined. Chance of the puncture depends on the dimensions of the insulators, steepness of the impulse voltages an d the number of impulse occurrences. Empirical equations relating to t hese parameters has been established based on laboratory test results. Calculation shows no risk of puncture on the quality insulators for t he impulse voltages of 2500kV/mu s steepness which is required by the standards.