Acoustic emission technique for detection and location of simulated defects in power transformers

Some of the practical limitations of conventional electrical method for measurement of partial discharge (PD), especially at site, have lead to the development of alternate methodologies. Acoustic emission (AE) technique is one among them. PD detection based on AE technique is gaining importance due to the advantages like AE technique is nondestructive, on-line, possibility of location of PD sources, etc and hence being tried as one of the on-line diagnosis tools for power transformers. During field testing of power transformers, in addition to PD signals, AE data acquired may contain acoustic emission signals from different sources like electrical, thermal, mechanical, environmental, etc. For realistic analysis of such AE data, it is essential to eliminate unwanted signals (noise). Different defects generate acoustic emission signals with different characteristics, which help in discrimination of PD from noise. This requires precise knowledge of the characteristics of individual sources. Simulation of known types of defects in power transformers has helped to study their AE characteristics and differentiate PD sources from noise source.