Light emission and electrical tree initiation in highly stressed XLPE and the effect of DC prestressing

In the last few years it has become established that electroluminescence (EL) is emitted prior to the growth of electrical trees in a range of polymeric materials. Previous workers have related light emission to the calculated electrical field even though it is known that space charges can influence the internal electrical field. In this paper light emission from cross-linked polyethylene insulated samples has been measured and an attempt has been made to alter the internal field using DC polarisation and to investigate any effects upon the emitted light.