Effects of electric field and temperature on space charge characteristics in double-layered polytetrafluoroethylene films

As the core component of composite insulation for dry-type high-voltage equipment, polytetrafluoroethylene (PTFE) films are subjected to high temperatures and complex electric fields. Therefore, this study explores the effects of electric field and temperature on the space charge characteristics of double-layered PTFE films based on the measurement of space charge distribution in double-layered PTFE films under different DC voltages and temperatures using the pulsed electro-acoustic measurement system. Results show that more charges accumulated in the PTFE sample subjected to a positive electric field during polarization and the space charges dissipated more rapidly during depolarization compared with those subjected to a negative electric field. The existence of a PTFE/PTFE interface increased the density of trap and deepened the trap. The positive charges that accumulated at the PTFE/PTFE interface during polarization gradually held a dominant position with the increase of temperature. Finally, the formation of charge in the PTFE/PTFE interface mainly depended on two factors. When the applied DC voltage was not large, the charge formation was mainly dominated by the Maxwell-Wagner polarization effect. When the voltage increased to a certain threshold, the charge formation was mainly caused by the charge injection and migration characteristics.