Real time measurement of space charge evolution in polyethylene under rapidly varying voltage stress

Recently an instrument based on the PWP method was set up to measure in real time the evolution of space charge distributions in solid dielectrics submitted to rapidly varying voltages. Successive measurement are performed at a frequency up to 3200 Hz. No signal averaging is required, taking into account the large signal to noise ratio of each measurement. This instrument is used to study the evolution of space charge in polyethylene (LDPE) plates submitted to high voltage pulses. The influence of the duration of the pulse (from 10 ms to 300 ms) and the amplitude of the applied field are analyzed. The buildup of the space charge shows a very non-linear dependence with respect to these two parameters.