An Analysis of the Unbalanced Three Phase Fault in the Transmission Line

Abstract

In this paper, unbalanced three-phase fault in transmission lines is considered with respect to estimating the state of power system after a fault occurs at different buses. Faults such as a single line to ground (SLG), line to line (LL) and double line to ground (DLG) affect the bus system that is connected along with the transmission line. MATLAB software was employed in which unbalanced fault programs based on the Symmetrical Component method to determine the voltage magnitudes and line current magnitude at Phase A, Phase B and also on phase C for the different bus lines. The unbalanced fault programs are executed for the standard IEEE 14, IEEE 26 and IEEE 30 bus systems to describe in details the effect of different faults at bus systems in terms of voltage and current magnitude. A Newton Raphson-based power flow program was used as well to determine real and reactive power for the different bus lines. The obtained results show that the single line to ground fault is the most severe kind for IEEE 14 bus system, while for IEEE 26 and IEEE 30 bus system, the most severe fault is line to line fault.