Detection of electrical tree initiation and assessment of shape of the developing tree using pattern recognition of partial discharge occurrence phase distribution

We have constructed a PD pulse measurement and degradation diagnosis system (PDM/ES-I) of materials suffering partial discharge using a personal computer. We applied PDM/ES-I to electrical tree degradation in low density polyethylene. The PD pattern measured at a given aging time was compared with five standard normalized PD patterns which had been registered in advance as five representative degradation stages. Consequently, the pattern recognition method proved to allow an exact determination of the time when the tree was initiated. In addition, the result of assessment agreed well with the observed tree shape