This thesis describes the development of a new directional relay for the ultra-high-speed protection of EHV transmission lines. The work has been carried out by utilising digital computer simulations, and the relay has been developed assuming that it would be implemented by micro-computer. This has enabled the use of a new digital filtering structure, which has been specifically devised to extract the superimposed quantities that the directional principle is concerned with. A modal transformation is utilised within the relay in order to define decoupled wave signals for a multi-conductor system, the transformation is also shown to provide significant hardware economies in the final design. In order to study the characteristics of the new relay, a number of new primary system digital simulations have been devised and are described in the thesis. These simulations include single and double-circuit multi-terminal systems with advanced fault capabilities. The novel decision process, in combination with the digital filter, enables the relay to provide a secure directional decision within typically, 2.5 ms of a fault occurring. Such an operating time will enable ultra-high-speed clearance of faults to be achieved, if the most recent circuit breaker developments and wide-band communication equipment are also employed.
|Date of Award||1984|