Light emission characteristics during the initiation of the electric tree in insulating polymers

Abstract

The light emission during the growing of the electric tree has been studied before, but very little is known about it before the electric tree initiation. The aim of this work is to study the light emission before electric tree initiation in insulate materials under high AC stress. The ultra-sensitive photomultiplier tube is used to detect the photons in a darkroom and a series of optical filters are used to investigate the spectrum of the photons. The existence of photons before tree initiation is proved and the pattern of them during an AC cycle is observed. The spectrums of the light emission in different dielectric materials are acquired and provide some evidence for the interaction between free charges and polymer molecules. Although the investigation of the light emission is far from being complete, it is found that the light emission under AC voltage starts with the recombination of opposite charges and the interaction process begins under a higher electric field. Based on the experimental results, a brief charge behaviour model is built up.