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

Abstract

The application of ultrasonic techniques for location of partial discharges(PD) in power transformers is now well established -for example as described in references 1 and 2. A sound wave produced by a partial discharge inside a transformer must in general pass through various barriers on its way to a transducer attached to the outside of the tank wall. If the PD source is located deep inside the coils, the acoustic signal generated by the discharge may not be detectable because of the attenuation of the signal and the relatively poor sensitivity of the detecting system. Enhancement of the signal can be realised using signal averaging techniques. However, for a transformer having more than one PD source and large interference, averaging of the acoustic signals from different sources may lead to confusing results even when a combined electric and acoustic technique is used.The present paper describes a method by which these problems may be minimised or overcome. 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[3,41 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 330kV/fl/3SMVA transformer in service have given encouraging results. An increase of the acoustic detection sensitivity by 20-40dB has been achieved.

Study of the Ultrasonic Characteristics of Typical Partial Discharge on GIS

“…The detection and diagnosis ofultrasonic signals generated by partial discharge (PD)from electrical equipment is called ultrasonic test method. When PDoccurs in GIS, the charge neutralization process will inspire steep current pulse,which incurs thepartial area where partial discharge occurs been heated and expanded, theexpansion areareturn to the original size after the PD process [4,5]. The changing size causes the instantaneous changes of density and generates the ultrasonic signals, which in the form of spherical wave from the partial discharge point and spread to the space around,stimulating all sorts of sound waves on the metal shell, such as longitudinal wave, shear wave and surface wave.…”

Taylor-genetic Algorithm on PD Location

“…Up to now, the location of PD has been successful in the factory and laboratory environment, as reported in literature [1][2][3][4][5]. The most successful location techniques are probably those based on the measurement of the time difference of arrival (TDOA) of the acoustic signals.…”

An extrinsic Fabry–Pérot interference fiber sensorfor ultrasonic detection of partial discharge

“…The more commonly used detection methods of the PD signal are pulse current method [8,9], ultra-high frequency detection method [10][11][12][13][14][15], ultrasonic detection method [16] and optical detection method [17][18][19][20][21]. Electric sensing method and ultra-high frequency method are susceptible to electromagnetic interference, but they are not suitable for PD sensing in a strong electromagnetic environment.…”