抄録
In order to propose a method for producing water trees that measure a few millimeters in length in 20kV class to 60kV class XLPE cables, we discussed defect types and thermal conditions. First, surface roughness, needle protrusions, and line cracks were formed on the XLPE insulation surface of 6.6kV cables, and it was found that the water tree grew to a few millimeters in length from the needle protrusions and the line cracks. Second, water trees were generated in XLPE sheet and cable samples at room temperature and under a heat cycle and continuous elevated temperature conditions. Here, the longest water trees grew at room temperature. From these results, we selected needle protrusions and line cracks as defects and set room temperature as an artificial water tree degradation method. This method was applied with needle protrusions to a 22kV class XLPE cable, and we found that water tree length reached a few millimeters and AC breakdown voltage decreased to approximately 35% of the initial value.
