A new method for signal averaging resorting to space charge measurements by the pulsed electro-acoustic method under AC stress

A new method for space charge measurement resorting to the pulsed electroacoustic (PEA) method under periodic stress of arbitrary waveform is presented. The originality of the work resorts to the use of a long memory digital oscilloscope combined to the method used to sample one period of the HV stress into several profiles. There is no need for synchronization between pulse generation and HV stress and hence no hardware change of classic PEA system. The pulse generator provides a probing pulse of 5 ns duration, at a maximum frequency of 1 kHz. With these features, one period of the AC frequency can be resolved into 200 profiles by frequency adjustment of the pulse generator. The typical measurement time is less than 20s for f > 0.2 Hz. Preliminary results obtained on a crosslinked polyethylene film under 50Hz ac stress are shown to demonstrate the feasibility.