Influence of water-tree degradation on electroluminescence spectrum in XLPE

We have studied electroluminescence (EL) and reported that EL activity in XLPE with dried water-tree degradation is higher than that in virgin XLPE. Dried water-treed XLPE is reported to contain excess number of micro voids and also polar groups different from those in virgin XLPE. EL spectrum is detected in the visible range in virgin PE and clearly distinguished from spectrum of partial discharge which exists in the UV range. Here we will report the existence of water-tree degradation changes EL spectrum in XLPE. EL spectrum peak appeared at 650 nm in virgin XLPE, but at 550 nm in dried water-treed XLPE. The EL spectrum change is considered to be caused by the formation of polar groups in water-treed XLPE