PERFORMANCES OF HIGH-VOLTAGE GLASS INSULATORS SUBJECTED TO FAST TRANSIENT OVERVOLTAGES

Steep-front, short-duration voltage pulses occur in power systems as a consequence of lightning, switching of the increasingly used gas-insu lated switchgears or by electromagnetic pulses of very high amplitude. Such overvoltages characterised by very fast rise time may produce ir reversible damages to the insulation of the different apparatuses of a n electric power line. Test results will be presented in this paper co ncerning the behaviour of cap and pin-glass insulators subjected to st eep-front overvoltages. In particular the effect of the glass composit ion on the insulator performance will be analysed for both normal and anti-fog configurations. Moreover; the dependence of the test results on the polarity of the applied voltage and the electrodes arrangement will also be discussed.