Fault Location For Un-transposed Parallel Transmission Lines

To meet increasing power demands, numerous EHV transmission lines have been used in the grid. Un-transposed and parallel transmission lines are adopted considering construction cost, power-carrying capacity, mountainous areas and the distance between generation sites and load center. Most EHV transmission lines are aligned and un-transposed, which will lead to unsymmetrical parameters of each phase. Conventional fault location algorithm based on symmetrical parameters are no longer applicable. So it is necessary to find a new way in locating faults for EHV un-transposed transmission lines.This paper presents a fault-locating method for EHV un-transposed parallel transmission lines which use merely the voltage and current data at local end. The method uses voltage equation for the fault phase of the fault line. The equation consists of fault distance, fault resistance, and fault current. Kirchhoff's voltage law is applied to the loops of three phases containing fault line and the parallel line to get the fault current. The fault current is represented in terms of fault distance. Inserting fault current into the voltage equation results in an equation that contains fault distance and fault resistance. The fault distance is estimated by solving the equation.EMTP simulation test results indicates that the algorithm is accurate in locating faults, regardless of the fault resistance and mutual coupling effects.