The laser induced pressure pulse technique for space charge measurements-a user's perspective

This paper discusses the difficulties in determining a calibration when very high electric stresses are used, particularly if the material under test contains charges with very high mobilities. An extended method for determining the calibration, which allows for the resolution of the very mobile charges is presented. This method can be applied to any fast non-destructive measuring technique such as the LIPP or PEA. The calibration procedure is discussed as applied to the LIPP technique and crosslinked polyethylene (XLPE) samples are used to illustrate the method. It is demonstrated that under high electric stress there is a very mobile space charge that will modify the internal electric stress distribution after very short periods of time. The mobility of these carriers may be sufficient to affect the performance of the insulation under ac conditions.