Acoustic emission from partial discharges in cable termination

An investigation by computer modelling was carried out to determine the nature of acoustic signal from partial discharges (PDs) in a model insulation system containing materials commonly used in cable terminations. These were polyethylene (PE), ethylene-propylene-diene monomer (EPDM) and silicon insulating fluid (SF). Two simple defect types were considered: spherical voids and fissures. Gaussian pulse point-source placed within the defect was used to model a PD event. The results showed that the relationship between the defect size and the acoustic signal frequency is governed by an inverse power law of the form f ~ 1/d in spherical defects and f ~ 1/(t^0.45w^0.48) in fissures. The frequency of sound emitted from defects of similar overall size was similar regardless of the shape.