Mechanism for Stimulated Acoustic Events associated with Partial Discharge

A mechanism is proposed for Stimulated Acoustic Events (SAE) observed as associated with Partial Discharge (PD) events. The mechanism is based on the formation of a transverse horizontal wave within a dielectric gap and propagating along the high voltage electrode — dielectric interface. The excitation of an extensional wave in the electrode and a large acoustic impedance mismatch at the electrode — dielectric interface are required (as first described at the 2006 IPMHVC). The frequencies in the ultrasound of both the fundamental and first harmonic components of the observed SAE are explained. The spatial shear displacement due to the transverse horizontal wave has been estimated and will be described. The maximum displacement is predicted in the dielectric, close to the high voltage electrode. The possibility that cyclic displacement resulting from SAE could nucleate voids that could then excite PD under voltage stress is explored.