The Growth of Electrical Tree and Its PD in Inner and Outer Layer of 110kV XLPE Cable Insulation

The growth of electrical tree in inner and outer layer of 110kV XLPE cable insulation was observed and its partial discharge was detected online. Because of the production process of XLPE cable, there are differences of the growth of electrical tree inside and outside the cable insulation with different voltages. Electrical trees in inner layer of insulation have bigger growth rate than the outer. With higher voltage, the situation is more obviously. When 9kV and 12kV added, there is a stage of PD disappeared before breakdown occurred, but PD persistence with 18kV and there are different changes in inner and outer layer of cable insulation.