Acoustic signal propagation in solid insulating materials

Polymeric insulating materials are considered as a crucial part of most high voltage components. The continuous high electric stress applied across the insulation material may, over a long-time duration, initiate partial discharges which deteriorate the insulation and lead towards dielectric failure. The detection of the acoustic pressure pulses generated as a result of partial discharges can be helpful in detecting and locating the PD at the initial stage. Detection of Acoustic Emissions (AE) is a well-established technique for gas and liquid insulation systems but is not fully explored in the public domain for solid insulation systems. In this work, propagation behaviour of the pressure acoustic wave in nylon 6,6 rods of differing lengths were analysed in the laboratory. The discharge events were created in air but near the surface of one end of the polymeric rod. The acoustic transducer was attached to the opposite end of the polymeric rod to detect the arrival of the propagated acoustic signal. It was determined, based on the first peak of arrival for all data, that the drop-in magnitude of the propagating pulses follows the 1/r2relationship where r is the distance away from the discharging site.