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

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, line current magnitude, total fault current, real and reactive power at Phase A, Phase B and also on phase C for the different bus lines. The unbalanced fault programs are executed using a Newton Raphson based power flow program for the standard IEEE 14, IEEE 26 and IEEE 30 bus systems. 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. This finding is crucial for evaluating the reliability and stability of power transmission lines.