Partial discharge in a cylindrical cavity in XLPE under DC voltage: Simulation and experiment

A simulation model is established to investigate the influence of applied voltage and temperature on DC partial discharge characteristics of a XLPE sandwich internal cavity sample. The field and temperature dependent conductivity of XLPE is considered, and its influence on the electrical field distribution is computed. The calculation results show that the voltage across the cavity changes with time under constant DC, and the steady cavity voltage is 32.7% higher than that just after voltage application. When calculating the cavity voltage at 70 °C, the error is over 500%, if the characteristics of the conductivity of XLPE is not considered. Residual cavity voltage with the opposite polarity after decreasing voltage is discovered by computation, and discharges with the polarity opposite to the applied voltage are detected by experiment. By simulation, the partial discharge repetition rate increases by two orders of magnitude when the temperature increases from 23 to 70 °C. The repetition rate measured by experiment increased by over one order of magnitude. The change of repetition rate is attributed to the reduction of cavity voltage recovery time influenced by the temperature dependence of the XLPE conductivity.