Transient based earth fault location in 110 kV subtransmission networks

摘要

This thesis deals with ground fault location in subtransmission networks. The main subject of the thesis is transient based ground fault location using low frequency fault generated transients. However, the thesis also considers the conventional fault location methods and reviews the various other methods. Low frequency transient based methods, in general, are more precise and more reliable than the conventional methods based on fundamental frequency. They also avoid the need for further investment in existing systems that would be required, for example, for the implementation of travelling wave fault location, as existing transient recorders can be used.As a byproduct of the thorough investigation of conventional fault location and the presentation of its properties and limitations, a new error estimation technique is proposed.Fault generated transients are presented and tested, and their potential to aid fault location using the phase or neutral current is studied. The thesis also tries to solve some of the problems related to fault transient generation and propagation, as well as measurements and signal processing. The network configuration and transformer neutral grounding type receive special attention. The thesis shows the network conditions under which the method works reliably and accurately, and for critical conditions it proposes appropriate correction factors. The studies are performed for the 110 kV overhead lines under the jurisdiction of Fingrid (the Finnish electricity transmission system operator) for all kinds of neutral configurations. The EMTP/ATP software package is used as the network simulator. The results of the simulations as well as real ground fault recordings are analysed and processed in a fault locator developed by the author and implemented in Matlab.