دانلود Elimination of DC component and identification of inrush current using harmonic analysis for power transformer protection

Abstract

This  paper  provides  an  estimation  of  transients and  method  of  elimination  of  decaying  DC  component  for  the purpose of power transformer protection. Further, the presented strategy discriminates different harmonics generated during power  transformer  energization  and  distinguishes  inrush  from  short circuit. The algorithm proposed in the relay logic disconnects  the  equipment  reliably  and  accurately  on  sensing fault  based  on  switching  instance,  switching  angle  of  the  circuit breaker and amplitude estimation of the current waveform generated during the fault. In order to verify the performance of the  proposed  algorithm,  off  line  simulation  of  the  power  system  model is carried out using MATLAB and observed the performance of the relay during inrush and short circuit phenomenon. In this paper a method has been proposed to estimate harmonics up to 5th order using MATLAB and a laboratory test results has been exhibited for analysis and interpretation with respect to a set threshold value. The laboratory  simulation  discriminates  internal  and  external  fault  from  inrush  current,  thereby  preventing  mal-operation  of  the  relay during inrush while tripping on a short circuit.