Location of partial discharges and diagnostics of power transformers using acoustic methods

Acoustic partial discharge location is used by all major transformer manufacturers during production test to locate discharge activity before significant damage can occur, and to minimise the time required to locate and rectify the fault. The method uses an array of high-frequency acoustic sensors, typically responding at up to 150 kHz, attached to the outside of the tank. These sensors are sensitive to the transient, structure-borne, acoustic signals resulting from partial discharge or arcing, whilst being insensitive to vibration and general noise. They contain electronics to amplify and buffer the signal making them virtually immune to electrical noise. Time arrival methods are used to locate the sources, in the same way that earthquakes are located, but extended to 3-dimensions. In the past, operators looking at the signals captured on digital oscilloscopes perform the source location, a highly skilled job which requires a continuous source. Systems have been developed and are being increasingly used which make greater use of software and computers to locate and characterise emissions.