Equivalent Transmission Line Model and Acoustic Characteristic Analysis of Measurement System of Pulsed Electro-acoustic Method

When using the pulsed electro-acoustic(PEA) method to measure space charge inside insulation materials, a characteristic evaluation of measurement system based on simulation methods is beneficial to the accurate analysis of charge results. For the acoustic propagation and transition in the measurement process representing charge signal propagation process, the modeling method of the equivalent lossy transmission line model of acoustic waves was proposed combining with the propagation principle of voltage wave in transmission lines. Based on the consistent simulation results and theoretical analysis on the electrode record point and transducer, the reliability of the model was verified. For the actual situation of reflected clutter signals existing in the measurement results, it is pointed out that the clutter signals may affect the measured effective signals when the frequency of pulse excitation is excessively high. Further simulation results indicate that the mismatch of acoustic impedances between semiconducting electrode and sample can affect the measured acoustic amplitude on the interface of upper electrode. Moreover, the mismatch of sound-absorbing material and transducer can influence the shape of waveforms. Finally, the simulation results of multi-layer sample show that the thickness of the sound-absorbing material should be much larger than that of the multi-layer sample to avoid the superposition effect of reflection. And the acoustic characteristic of an actual PEA measurement system can be effectively evaluated by the simulation model. © 2021, High Voltage Engineering Editorial Department of CEPRI. All right reserved.