Comparison and Analysis of Magnetizing Inrush and Fault Condition for Power Transformer

Abstract

This paper presents the second harmonics present in the primary current of a power transformer at different conditions using Fast Fourier Transform and Total Harmonic Distortion techniques to analyze the inrush condition and to distinguish it with fault condition of a power transformer. Result shows that the 2nd harmonic content is pre-dominant in inrush condition of primary current of the power transformer. It is observed that there are significant differences amongst the parameters found during inrush condition, normal condition and internal fault condition which are useful in the identification of magnetizing inrush current of power transformer. The simulation is done in MATLAB/SIMULINK.

Mitigation of magnetising inrush current in three–phase power transformer

“…And after 1 second, it comes up to around 200 A. There is a DC component present in inrush current waveform and is rich in second harmonics [2]. The presence of DC component slows down the response of protection system and generally deteriorates the discrimination ability of the relay.…”

“…Thus, flux in the transformer is a function of the residual flux, instant of switching, magnetic properties of core. This current has various disturbances on transformer attribute: reduced life-span, major voltage drop, insulation weakening, electrical and mechanical vibrations in coils, difficulties in protecting relays and all leads to poor power quality of the electric system [2][3][4][5]. Many inrush current mitigation techniques have been proposed over the years each with its own advantages and disadvantages.…”

Differential Protection of Power Transformer using Wavelet Transform

“…This is mainly due to the high magnitude of inrush current. The difficulties produced due to the occurrence of magnetizing inrush are the inappropriate operation of the machines, failure of relay systems, unbalanced voltage in the transformer windings, increase in voltage drop in the power system during energization of power transformer [1].…”