System unbalance effect on faulted distribution systems: A numerical study

This paper presents a numerical study of the system unbalance effect on system voltage and current calculation during asymmetrical faults. Two different system operational conditions are tested considering a voltage imbalance at the substation bus: balanced system loads and voltage imbalance equal to 3.65% due to system loads. Five fault impedances are simulated. Two fault analysis methods, the symmetrical components and phase component algorithms are implemented and analyzed based on numerical simulations of asymmetrical faults on the IEEE 13 bus test feeder. The results show the accuracy of each fault analysis method and how the errors may vary according to the system pre-fault unbalance operation condition and the fault impedance.