Fundamental aspects of fault location algorithms used in distance protection

The paper considers fundamental problems involved in the precise location of faults on high-voltage transmission lines. The influence of pre-fault load on the distance-to-fault measurement problem is analysed and a new method of accounting for load effects is presented. Two of the algorithms considered are precise, containing no simplifying assumptions and their overall accuracy is limited only by the accuracy of digital impedance relays at both ends of the protected circuit. A third algorithm presents a new approach to the fault location problem, which requires digital impedance relays at one end only of a transmission line. The procedures described are applicable to any system arrangement and are suitable for a wide range of fault resistance values.