Study of Steep Impulse Voltage Characteristics of Suspension Insulators

Transmission and distribution lines are sometimes hit by lightning strokes and there is some risk of electrical puncture of suspension insulators due to high and steep lightning surge voltage. When the insulators suffer from steep lightning surge voltages, solid insulating body of the insulators is sometimes punctured before external flashover in the air occurs. These characteristics were investigated on the insulators at the laboratory by using different steep impulse voltages. From the investigation results, both V-t characteristics of external flashover and internal puncture were obtained on the insulators. And it was found out that the puncture of the insulators is a matter of probability, depending on the dimensions of the insulators, steep impulse voltages and number of impulse voltage applica-tion. Especially, effect of number of voltage application on puncture probability was clarified and partial damage by a small number of voltage application was verified before complete puncture occurred. Based on the study results empirical equation relating to probability of puncture (P), impulse voltage (V) and number of voltage application (N) was established.