Evaluation of Partial Discharge in Power Transformers by Acoustic Emission Method and Propagation Modeling of Acoustic Signal

Abstract

Transformers are one of the most important and costly components of any power system. Proper monitoring of the health of a transformer is thus inevitable. 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. Common insulation in power transformers are pressboard and oil. Unconventional PD measurement was developed for several decades ago as a form of PD detection system. In these PD measurement systems that are named unconventional method PD is analyzed by indirect features of this phenomenon, which includes electrical, acoustic, UHF, optical, and chemical methods. The main advantage of unconventional method is the ability of this method in order to decrease the amount of signal to noise ratio for on-site or on-line measurement. A study of the correlation between acoustic emission signals generated by PD and electrical PD charges is inevitable. By developing the speed of measuring devices like digital signal processor (DSP) the possibility of evaluation and calculation of acoustic signals in very short time have been increased. The aim of this paper is evaluation of acoustic signals for two different kind of pressboard (new and aged) with two types of sensors (75 kHz and 150 kHz peak frequency) and simulation of Acoustic Emission (AE) signals propagation which are produced due to PD inside a sample transformer tank by using Finite Element Method (FEM). 