An improved electric/acoustic method for the location of partial discharges in power transformers

A combined electric/acoustic method was utilized for PD (partial discharge) detection on a 330-kV transformer at site. The electrical pulses on the HV and neutral terminals of a transformer and the outputs of two acoustic transducers attached to the tank wall were measured by a four-channel digital transient recorder. The ratio of magnitudes of the electrical signals after filtering by a digital filter of a predetermined frequency band for the winding was used to discriminate acoustic signals from different PD sources. The signals from the same PD source were then averaged, resulting in significant suppression of the interference from mechanical vibration and from other PD sources. Tests on a 330-kV/√3/35-MVA transformer in service have given encouraging results. An increase of the acoustic detection sensitivity by 20-40 dB has been achieved