This thesis presents the development of a new approach to EHV transmission line protection based on fundamental principles. The method is based on a travelling wave approach and utilises analysis of spectral information derived for the transient phenomena caused by fault inception. By establishing practical means to utilise a frequency bandwidth of about 70-400kHz, a new protective-scheme could be developed to operate on detecting HF current components due to travelling waves set up by the inception of a fault. Thus, the scheme operates at ultra-high-speed and can detect a fault within a fraction of a millisecond. It possesses its essential discriminative feature by virtue of applying line wave traps (LWTs) installed at each end of the protected line. The locations of these traps define the zone of protection that is formed due to the combined effect of both the trap and the station bus-bar capacitance which in turn provides correct termination of the transmission line when over the requisite frequency-bandwidth. Thus, in-band current components will ideally not be able to pass through LWTs when these are set up due to external faults. The performance of the scheme was successfully demonstrated by digitally simulating many different test conditions. It is a non-unit scheme, that does not require communication channels, but it nevertheless possesses the features of unit schemes. It can cater for the protection of whole length of line when faults occur near voltage-maximum point-on-wave and also covers relatively high resistive fault conditions. The scheme may also provide a solution to lonstanding problems encountered in the protection of series-compensated transmission lines. In this respect, further investigations may now be performed in order to examine the possibility of achieving this goal.
|Date of Award||1984|