The effects of cross-country fault to the power system

Abstract

Cross-country fault are more likely to occur on double circuit transmission lines located on the same tower structure. The occurrence of cross-country fault on transmission line will cause complex analysis such as unusual current distributions that compromise the seen impedance by units not directly involved in the fault loop, giving fault selector problems for close-in faults. The complex analysis may have effects on currents and the performance of distance relay. In accordance to this, the project will study the effects of cross-country fault to the power system and later analyze these effects. The modeling of line network with the occurrences of cross-country fault is simulated by using CAPE software. The simulation is conducted on 115kV parallel line network whereby there were six phase of conductor which are three phase for circuit A and three phase for circuit B. Since the cross-country fault occur when there are two simultaneous one phase to earth fault, so there will be 3×3 which equal to nine combination of cross-country fault at an instantaneous time. All of these nine combinations of fault are simulated for distance less than 100 km for each line and also under zero fault impedance. The effects of cross-country fault to the power system are expected to be in terms of faulted phase, fault location, breaker tripping sequence and tripping time. It is found that the value of cross-country fault currents are changing when the faults are placed on different location of the parallel line network and the fault current will only be affected by the location of fault on parallel line network. The fastest tripping time for this network is 0.033 sec while the latest tripping time is 0.042 sec. In the end, the effects of cross-country fault can be studied by constructing the double line circuit and applying two simultaneous single lines to ground fault to the parallel line network by using CAPE software.