Analysis of Propagation Paths of Partial Discharge Acoustic Emission Signals

Transformers are one of the most important and costly components of any power system. Proper monitoring of the health of a transformer is thus indispensable. Online monitoring of partial discharges (PD) is one of the ways by which the risk of catastrophic failure of a power apparatus can be reduced. The acoustic emission method for PD measurement has numerous decisive advantages over the electrical measurement method. The acoustically emitted (AE) waves due to PD tend to propagate along various paths before being detected by the sensors. This paper analyses the results obtained from theoretical analysis of various propagation paths. It also analyses the experimental signals by applying various filtering techniques. A correlation between the theoretical and experimental results is thus established. Hence, by applying filtering techniques, it is possible to ascertain the peaks of the direct path and indirect path AE signals respectively and this can significantly reduce the error during the application of the PD source location algorithms, as more accurate time difference is now available. In the system under consideration, acoustically emitted signal produced by the PD are detected by the sensors mounted on the tank surface, stored on an oscilloscope and fed to a computer for analysis. For the theoretical analysis, the physical properties & features, of the transformer tank metal (steel) and the transformer oil are taken into consideration.