Although polymer insulators have been used by industry for more than thirty years, wide-spread use occurred in Australia only at the beginning of the nineties [1]. Currently there are more than thirty thousand medium and high voltage EPDM and PDMS units installed in Queensland, Australia. Premature ageing of polymer insulators is a major fear for utilities. It has been reported that degradation of one type of polymer insulator with subsequent flashover occurred just within six months after installation of the insulator [2]. The ageing of insulators has been found to be usually caused by the presence of discharges on the polymer surface. Discharges usually occur between water drops on the insulator shed and create a number of radicals and ionised species which may chemically react with the insulator surface and thus alter the original properties of the insulator material. The situation is further aggravated by relatively high temperature of such discharges which thermally degrade the insulator surface [3]. Changes in the material surface properties due to these effects may cause a flashover to develop across the insulator.
展开▼
