Decaying DC Offset Removal in Fault Current Signals of Digital Relays Based on LMSR Method

In this paper, a new method for estimation and removal of decaying dc offset from fault current signal using the Least Median of Squares Regression (LMSR) method is proposed. The fault currents include the decaying component and the mentioned component reduces the speed response and validity of grid protection relays. The proposed algorithm can foresee the dc decaying component and disassemble it from the fault current wave in a period of the wave cycle. as well as it has used from conventional fast Fourier equations to measure the phasor magnitude and fault current wave in grid protection relays which are mean the dc decaying magnitude and time constant is estimating by integrating fault current during one period cycle. The dc decaying component by deducing the ever sampling of a cycle wave in one period. About the fact that the mentioned proposed method creates the best performance, the simulation has been applying in PSCAD/EMTDC. the results of this work illustrate that the proposed method can foresee the component from fault current wave, as well as this method, could apply as phasor derivation in digital protection relays.