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Abstract

This thesis describes the simulation of an adaptive digital distance relay suitable for transmission line protection on line applications up to 250km in length.

The relay calculates the line impedance by solving the first order differential line eguation. To remove travelling wave distortion and transducer noise, the relay incorporates an adaptive filtering arrangement. This allows the relay to provide ultra-high-speed operation for faulted waveforms which do not require extensive filtering, yet provides discrimination and very-high-speed operation for more distorted waveforms.

To improve the reach point accuracy and fault resistance coverage for high resistance earth faults, the earth element characteristics, which are based on quadrilaterals, are adapted to the prospective fault condition by swivelling the characteristics according to the postfault zero sequence current. It is shown that the resistive to reactive reach ratio of the relay may be set to 3 without gross overreaching of the relay or particular reference to the line application.
The relay incorporates a novel power swing blocking feature where power swings and three-phase faults are reliably differentiated by checking for filter transients which are shown to be always present for three-phase faults but not for power swings. This arrangement gives the advantage that faults occurring during the power swing period will be detected by the relay. A study on part of a 400kV system subjected to a power swing shows that the relay successfully blocks.

Results are presented for reach point accuracy and operating time for single phase to earth, phase to phase and three-phase faults, where particular emphasis has been placed on the effect of harmonics, source short circuit level, prefault loading and fault inception angle. Fault resistive coverage is comprehensively investigated and results compare the difference between adaptive and fixed characteristic relays for short and medium line length applications.

Publication Type:	Thesis (Doctoral)
Subjects:	T Technology > T Technology (General) T Technology > TA Engineering (General). Civil engineering (General) T Technology > TK Electrical engineering. Electronics Nuclear engineering
Departments:	School of Science & Technology > Engineering School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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