The partial discharge characteristic of typical XLPE cable insulation defects under damped oscillating voltage

The oscillating wave test system (OWTS) which is similar to power frequency test system can be used to test the partial discharge of cable insulation defects. It is proved that using OWTS can bring many benefits such as it can make the test result be normative, and is not harmful to cable insulation which is totally suitable for field test. In order to study the PD characteristic of XLPE cable under oscillating wave voltage, four typical defects at different severity are designed to withstand the test voltage. The four defects are: A) the air-gap defect located at the cable joint, B) the cusp of semi-conducting layer, C) overly long or overly short overlap of stress cone joint, D) metal cusp at high potential. The experimental result shows that the partial discharge of different defects occurs at different phases which concentrate at 30°-70°, 220°-250°, while the number and quantity of discharge are quite different. The obvious differences between the four typical defects may lay a foundation for the further study on pattern recognition of XLPE cable. The typical damped oscillating voltage can be divided into 8 parts, the PD characteristic of XLPE cable under every part is also studied in this paper. After reading this paper we will have a deeper understanding of the PD excitation theory of oscillating wave.