Adaptive overcurrent relay (AOCR) based on Fano Factors of current signals

Abstract

A Fano Factor-based adaptive overcurrent protection scheme, that automatically adjusts the protection settings in response to the prevailing conditions of the power system, is presented. Both phase and ground overcurrent relays are based on the same mathematical algorithm to calculate the operating time using Fano Factors (FFs) estimated for phase and ground current signals, respectively. Effectiveness of the proposed adaptive overcurrent method is validated for various fault types under a plethora of loading current levels, besides a wide range of fault inception angles and fault resistance. Simulation results confirm that the proposed algorithm can detect series and shunt faults, differentiate between grounding and phase faults, and adapt the relay operating time settings using the FF for all conditions examined. The relay algorithm speed and sensitivity are controllable using both the FF setting values and moving data window size. Moreover, it is characterized by being simple, reliable, accurate, and can be implemented practically as a base of digital protective relay for use in substation automation systems and phasor measurement units.