Fuzzy Logic Based Scheme for Directional Earth Fault Detection and Classification

This paper presents a fuzzy-logic-based protection scheme for detecting the direction of earth faults in a transmission network using polarized voltage. The IEEE 9-Bus transmission network has been used to test the fuzzy logic scheme in MATLAB/Simulink. The proposed scheme involves the measurement of RMS value of each phase voltage in order to detect occurrence of a fault; the direction of fault is determined by measuring the phase angle between the fault current and the polarized or reference voltage. The proposed scheme has been tested in six earth fault cases, faults in the forward and reverse direction per phase. The simulation results demonstrate that the proposed protection scheme is able to detect earth fault and classify the fault direction accurately within one cycle time.