New fault location method for HV T-connection transmission lines

In the conventional fault location method, the fault section is first identified, and then, three-terminal lines are converted into two-terminal to calculate the fault location. However, when the fault occurs nearby the T-connection point, particularly in the case of high resistance grounding, the method cannot identify the fault section precisely and has a dead band. To overcome the shortcoming, this paper presents a new fault location method for teed lines, assuming the fault occurs at each of the three branches respectively, then calculating the teed node voltage and current flowing to the assumed fault branch. In the three fault distances calculated, the only one greater than zero and less than the corresponding branch length is for the real faulty branch. The proposed method can locate faults without having to identify the fault section first and can accurately locate the faults occurring near the teed node through large resistance. The fault location accuracy is independent of the fault resistance and fault type in theory. In addition, pre-fault data or filter is not required. Simulation results with EMTP indicate that the method is correct and accurate.