The space charge decay of high density polyethylene under different temperatures and accumulation fields

Polyethylene is a material that is widely used as insulation for power cables. In this paper, the space charge decay of high density polyethylene under different temperatures and accumulation fields is described. On voltage application both positive and negative space charge was found to accumulate rapidly in the bulk of the samples. The amount of positive space charge present increased with increasing voltage. An application of 5KV at temperatures 25-60°C gave mainly negative space charge, whereas voltages 8-23kV gave much more positive charge than negative charge. Charge accumulation was found to be rapid after voltage application. On short-circuit the main part of the space charge disappeared within a few tens of seconds. The decay time of the positive space charge decreased either with increase of the magnitude of applied voltage before short circuiting or with increase of temperature. It was suggested that the decay rate of positive space charge in HDPE was enhanced by temperature and the field produced by the accumulated space charge in the bulk.