A Study on PMU Based Fault Location Algorithms for Transmission Networks

This dissertation presents multi-terminal fault location algorithms for power transmission networks and multi-terminal transmission lines based on Synchronized Phasor Measurement Unit (PMU). In the past, it was difficult to precisely synchronize the sampling at the ends of transmission lines due to the lack of a common timing reference. It is widely recognized that the multi-terminal fault location algorithms are subject to errors resulting from unsynchronized sampling clock. Use of a timing signal from Global Positioning System (GPS) can greatly reduce or eliminate the synchronization errors from the measurements.
First, we propose a new concept of fault location observability for transmission networks based on PMUs. The aim of this work is to improve fault locating accuracy of transmission networks using limited PMUs. Generally, the number of installed PMUs is typically much lower than the number of substations in a transmission network. Under normal conditions, power engineers may be able to determine power system state from the synchronized data of a few PMUs installed at cardinal power system nodes. When a fault occurs, it is very hard to accurately locate the fault position using the data provided from limited PMUs, unless we install PMUs at all substations of transmission network. However, it would be very uneconomic to install PMUs at all substations. Thus, we present a new fault location algorithm to meet those needs (accuracy and economy). In the beginning, we propose a minimal PMU placement strategy for fault location observability and then develop a novel fault location algorithm using minimal PMUs to classify fault section and calculate fault location for transmission networks. An EMTP/ATP simulation of a 345 kV system is conducted to evaluate the performance of the proposed algorithm. The tested cases include various fault types, fault locations, fault resistance, fault inception angles, etc. The study also considers the effect of various buses. Simulation results indicate that the accuracy of the proposed algorithm is better than 99.363%.
Second, we also present a new PMU-based fault location algorithm for multi-terminal transmission lines. The development of the algorithm is based on distributed transmission line model and synchronized positive sequence voltage and current phasors. The method is an analytical solution and its computational cost is very low since it does not require iterative operations. The EMTP/ATP simulation was conducted to verify the accuracy of the method. The simulation studies show that the algorithm provides a high degree of accuracy in fault location under various fault conditions such as fault types, fault positions, fault path resistance, pre-fault load flows, and line shunt capacitance, etc. The average fault location error under various fault conditions is well below 1%.