Influence of Clamping Pressure on Measured Signals for Space Charge Measurements of Cables using Pulsed Electro-acoustic Method

This study investigates the effects of clamping pressure on measured signals when attaching measurement sensors to cables for space charge measurements using the pulsed electro-acoustic (PEA) method. The results reveal variations in amplitude and frequency characteristics with clamping pressure, particularly at high temperature compared to room temperature. To investigate the causes of these changes, structural and acoustic field analyses were conducted, and the analyses have qualitatively reproduced the amplitude variations observed experimentally. In addition, analysis of acoustic waves reaching the piezoelectric transducer revealed that increasing clamping pressure causes waves to deviate from ideal cylindrical propagation and shift towards plane-like propagation, enhancing the signal strength from the outer side of the cable insulation. The currently proposed signal recovery method for acoustic attenuation does not account for such transitions in acoustic wave propagation, leading to inaccuracies in estimating the acoustic attenuation function. Consequently, these inaccuracies affect the precision of converting measured signals into charge and electric field distributions. These findings highlight the critical importance of minimizing and standardizing clamping pressure to ensure the accuracy and reproducibility of space charge measurements using the PEA method.