Power system faults normally result in system damage, profit loss and consumer dissatisfaction. Consequently, there is a strong demand on precise and fast fault location estimation for power system to minimize the system restoration time. This paper examines a method to locate short-circuit faults on a distribution system with unbalanced loads without fault type information. Bus impedance matrix technique was harnessed in the fault location estimation algorithm. The system data including line impedances, source impedance and distribution system layout was assumed to be known factors, hence pre-fault bus impedance can be calculated and implemented into the algorithm. Corresponding methods to derive system matrix information were discussed. Case studies were performed to evaluate the accuracy of the fault location algorithm and illustrate the robust performance under measurements errors influences, load variation impacts and load compensation implementations. Traditional fault location methods involve current and voltage measurements mandatorily locating at each ends of faulted section to locate the fault. The method examined finds fault location for distribution system utilizing impedance matrix accompanied with sparse measurements in the power network. This method fully considers the unbalance of distribution system.

In modern power transmission systems, the double-circuit line structure is increasingly adopted. However, due to the mutual coupling between the parallel lines it is quite challenging to design accurate fault location algorithms. Moreover, the widely used series compensator and its protective device introduce harmonics and non-linearities to the transmission lines, which make fault location more difficult. To tackle these problems, this dissertation is committed to developing advanced fault location methods for double-circuit and series-compensated transmission lines. Algorithms utilizing sparse measurements for pinpointing the location of short-circuit faults on double-circuit lines are proposed. By decomposing the original network into three sequence networks, the bus impedance matrix for each network with the addition of the fictitious fault bus can be formulated. It is a function of the unknown fault location. With the augmented bus impedance matrices the sequence voltage change during the fault at any bus can be expressed in terms of the corresponding sequence fault current and the transfer impedance between the fault bus and the measured bus. Resorting to VCR the superimposed sequence current at any branch can be expressed with respect to the pertaining sequence fault current and transfer impedance terms. Obeying boundary conditions of different fault types, four different classes of fault location algorithms utilizing either voltage phasors, or phase voltage magnitudes, or current phasors, or phase current magnitudes are derived. The distinguishing charactristic of the proposed method is that the data measurements need not stem from the faulted section itself. Quite satisfactory results have been obtained using EMTP simulation studies. A fault location algorithm for series-compensated transmission lines that employs two-terminal unsynchronized voltage and current measurements has been implemented. For the distinct cases that the fault occurs either on the left or on the right side of the series compensator, two subroutines are developed. In additon, the procedure to identify the correct fault location estimate is described in this work. Simulation studies carried out with Matlab SimPowerSystems show that the fault location results are very accurate.