This thesis describes the engineering of a new prototype ultra-high-speed directional comparison relaying equipment, for the protection of EHV power transmission lines. The relay has been implemented using state-of-the-art microcomputer hardware and digital signal processing techniques, and is based upon a preliminary CAD design study. The basic operating principles which are central to the relaying scheme are discussed, together with the main features of the background CAD design. Relay operation has been verified in the laboratory by applying simulated power system fault waveforms, via programmable-transmission-line test equipment. Unique Noise Monitoring Trials have been performed, by installing the relaying equipment, together with associated, monitoring instrumentation, at the CEGB Cellarhead 400kV substation, in order to evaluate the levels of power system generated noise, and its effect on relay sensitivity and stability. These trials have been responsible for a significant contribution to the understanding of background superimposed disturbances on power systems. The subsequent analysis of site data has identified a number of problem areas with respect to the operation of the relay in a power system environment. These have been addressed, and a number of important refinements to the relay design have been proposed. Finally, several power system faults, internal and external to the protected line section, were detected during the site trials, of which four have been discussed in detail with the aid of recorded waveforms.
|Date of Award||1985|