Influence of interfacial condition between film and lower electrode on space charge measurement

One electrical insulation evaluation technology is the pulsed electroacoustic method, which detects the acoustic pressure due to the space charge in the bulk. To improve its reliability, a measurement system for the apparent acoustic impedance of the sample is introduced into the space charge measurement system. The apparent acoustic impedance of a polyethylene terephthalate film increases as the applied mechanical pressure increases. The position of the lower electrode signal shifts under a lower mechanical pressure and magnitude of the lower electrode signal decreases. The larger silicone oil layer lead to a charge shift due to interfacial polarization and a smaller magnitude of the pressure wave generated from the interface between the silicone oil layer and the sample.