Influence of repetitive application of damped AC voltage on insulation performance of water tree aged XLPE cable

The authors have confirmed that most major cause of degradation for 6 to 60 kV class XLPE cable in Japan is water trees with needle shape, which would develop only a few in an XLPE cable with its length of 100 m or so. Therefore, establishment of the detection and diagnostic methods for such water trees is important for degradation assessment and lifetime prediction of aged XLPE cables. The authors have focused on the application of damped ac high voltage (DAC) combined with partial discharge measurement for the water tree diagnosis. This paper deals with the influence of repetitive application of DAC on the insulation performance of water tree aged XLPE cable in order to confirm harmlessness of DAC application from viewpoint of partial discharge characteristics.