Effect of Acoustic Wave Reflections on Space Charge Measurements with PEA Method

Abstract

The Pulsed Electro-Acoustic (PEA) method is the most used technique for space charge detection in solid dielectrics. The methodology is largely employed in the field of High Voltage Direct Current (HVDC) transmission and is based on the detection of acoustic waves generated by charges vibration. One of the most common problems arising during the detection is the presence of multiple reflections taking place due to the presence of means discontinuity in the different PEA cell components. This reflection phenomenon, if not well taken into account, could cause incorrect interpretation of the PEA output signal. It is easy to understand that a simulation model is a basic tool to understand the waves behavior within each PEA cell component and finally to correctly interpret the output charge profile. Furthermore, a simulation model turns out to be useful for assessing what samples can be tested with an available PEA cell without reflection in the main signal. In this work, the PEA cell has been modeled in Matlab environment and the waves behavior has been simulated by using a numerical method. The model has been validated theoretically by making a comparison with the results of another work found in literature. In addition, the good performances of the model have been confirmed by experimental validations carried out using two different PEA cells.