Propagation and Partial Discharge Characteristics of Electrical Trees in XLPE Cable Under High Temperatures and High Gas Pressures

The gas produced by electrothermal aging of cross-linked polyethylene (XLPE) insulation material will produce a local high pressure in the insulation layer of cable. In order to study the effect of partial pressure on electric dendritic growth and partial discharge characteristics of cable at different temperatures, using XLPE short cable as a sample to build the test system, we studied the growth law and partial discharge characteristics of electric tree of cable under different temperatures acting on the inner wall of insulation layer. The experimental results show that, at a low temperature, the XLPE is in the glass state, the material in the initial stage has good mechanical properties, and the increase of air pressure has no effect on the initial release and growth. In the late stage, the sharp increase of partial discharge causes the area of the needle to soften and deform under the pressure, and the electric branch develops rapidly along the stress concentration zone. XLPE is in a high elastic state at high temperature, and the free volume integral number increases. The higher the pressure, the greater the axial tension of the insulating material, the more obvious the electrical properties of materials are, the more easily the electric branches are raised. At a high temperature and high pressure, the insulation performance of XLPE cable decreases obviously, and the stable operation of cable is seriously threatened. © 2018, High Voltage Engineering Editorial Department of CEPRI. All right reserved.