Charge accumulation in LDPE and XLPE conditioned at 80/spl deg/C under reduced pressure

The effects of thermal conditioning, under reduced pressure, on space charge accumulation in planar LDPE and XLPE samples under DC stress, have been investigated. The samples were conditioned prior to voltage application by being held at 80/spl deg/C for 2-3 days in short circuit at rotary pump pressure. Some were then cooled to room temperature over a period of at least 6 hr, still under rotary pump pressure and in short circuit, while others were cooled to room temperature in less than 1.5 hr in the laboratory air. DC fields of 18 kV/mm were then applied at room temperature, and space charge accumulation was monitored as a function of time using the PEA (Denmark) and LIPP (Australia) techniques. Conditioning did not prevent space charge accumulation in either the LDPE or XLPE samples.