Steep-front impulse voltage tests of composite insulators /

It is very important to eliminate improper insulator designs and technological faults. The most sensitive parts of non-ceramic insulators (NCIs) are their microscopic and macroscopic interfaces. In this paper our experiences with the steep-front impulse voltage test are presented. According to the IEC standard, after the action of thermo-mechanical loads samples of NCIs are subjected to steep-front impulses with steepness s 1 kV/ns. Each impulse should cause an external flashover without any puncture of the tested NCI sample. A setup which makes it possible to produce steep-front impulse voltage with steepness in a range of 1-4 kV/ns has been constructed. Specially prepared samples of NCIs were tested by applying such impulses. The obtained results indicate that even 4 kV/ns pulses do not damage properly manufactured insulators. Moreover, the steepness is more selective than the standardised 1 kV/ns impulse for badly made insulators.