Space charge signal interpretation in a multi-layer dielectric tested by means of the PEA method

Since a few decades, the pulsed electro acoustic (PEA) method is used for measuring space charge in insulating materials. Through the years, the PEA method has been mainly applied on flat homogeneous dielectrics. However, this technique has been recently used on multi-layer dielectrics as well. In this case, particular attention must be paid to the calibration of the measuring system and to the interpretation of measurement results. In fact, when a combination of different materials is tested, the dissimilar acoustic and electric properties of the materials affect the detected space charge signal. Besides, the measurement results can also be influenced by the presence of interfaces within the sample. In this paper, the authors discuss the generation, transmission and reflection of the acoustic signal in a multi-layer dielectric tested by means of the PEA method. Based on the proposed analysis of the acoustic phenomena occurring in a two-layer test object, the results of a PEA measurement were evaluated.