Space charge measurements on impregnated paper: a review of the PEA method and a discussion of results

In electrical insulation in high voltage equipment being serviced under dc stress, space charge is often present. This change greatly influences the electrical field. Quantitative knowledge about the presence of space charge is therefore needed. This paper describes the quest for useful measurement principles. One measurement principle, the Pulsed Electroacoustic method, will be described extensively. The method of calibration and the importance of knowledge about the frequency response of the system are described. The results of space charge measurements on impregnated paper samples are presented and discussed, along with a model that predicts the observations fairly well.