Impedance Analysis of Buffer Layer of High Voltage XLPE Cables

When the buffer layer of high voltage XLPE cable is ablated, white powders often appear at the contact position between water blocking tape and aluminum sheath, which changes the impedance of the buffer layer. In order to study the impact of white powders on the buffer layer impedance, an impedance circuit model of buffer layer in 110 kV XLPE cable was established, and the amplitudes of the new buffer layer as well as the defective one at different lengths were simulated and calculated by Simulink. Also, the repairing method for cables with white powder defects is studied, by replacing the water blocking tape with the new one in different positions and some suggestions were given. The results have shown that the buffer layer with white powder defects will significantly increase the impedance between the cable insulation screen and the aluminum sheath. The impedance of the new buffer layer is almost unchanged with the length increasing, while the impedance of the water blocking tape with white powders decreases with the length increasing and gradually tends to a steady value. Using replacement units with good conductivity in different positions of the defective cables can provide a reference for the remediation of cable buffer layer defects with white powders.