Accurate fault location for power transmission lines

This thesis describes a new accurate fault location technique for power transmission lines. The technique is based on a distributed parameter line model which inherently accounts for line conductor asymmetry and shunt capacitance. The accuracy of the new technique is not significantly affected by fault resistance, source network configuration or line length. Also, in most cases no fault type identification is required. The new fault location technique uses the current and voltage phasors at power frequency measured at the line ends. These measurements are synchronised from a knowledge of the prefault phasor data. For a single-phase network the basic idea is to equate two equations obtained for the fault point voltage; one from the sending end phasor data and the other from the receiving end phasor data. The resultant equation is solved for the distance to fault. For multiphase systems the idea is 'generalised by using the theory of natural modes which involves the evaluation of eigenvalues and eigenvectors of the lines. In this way a multiphase system is decoupled into a number of single-phase modal circuits; each circuit can be solved for fault location. For perfectly transposed lines the eigenvalues can simply be evaluated from the sequence components and a real eigenvector matrix can be defined for all the lines. For untransposed lines the new algorithm maintains its high accuracy when assuming perfect transposition to simplify the evaluation of eigenvalues and eigenvectors. Also for double-circuit applications a circuit-by-circuit fault location, without any link between the two circuits, is possible. The test results for different fault conditions presented in this thesis show the higher accuracy in fault location achieved by the new,algorithm in comparison with the algorithms used in the best commercially available fault locators.