Space charge dynamics and electric field distortion in the laminated insulation for HVDC cable

Polypropylene laminated paper (PPLP) is an important composite insulation which has been successfully used in oil filled (OF) cable, mass impregnated (MI) cable and high temperature superconductor (HTS) cable. PPLP is an improved insulation based on conventional cellulose Kraft paper. It is made of one PP film sandwiched between two Kraft papers. The space charge distribution in DDB oil impregnated PPLP sample under DC electric field has been investigated by the pulsed electroacoustic (PEA) technique in this paper. The electric field distribution and distortion have been discussed based on the results obtained from one, two and three layers of PPLP sample. The results show that space charges start to accumulate at the interfaces between paper and PP with time. As a result, the electric field created by the accumulated space charge within the PP film has been enhanced while the electric field in paper reduced. The more the charge accumulated, the higher the electric field distortion in the PP film. The charge distribution and electric field distortion present repeatable pattern in multilayered PPLP sample.