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Abstract

This thesis describes an adaptive digital distance protection scheme suitable for Teed transmission line applications. The scheme utilises the line and source impedances in order to measure the exact line impedance at the reach point and gives correct discrimination between in-zone and out-of-zone faults.

The relay requires some information about the system operating conditions at the remote terminals. This data is not required in real-time but has to be available at the measuring point. Thus, the speed and accuracy during a fault is not affected.

The implementation of the scheme requires a central computer system where information about the system operating conditions can be provided. The update at the relay is initiated by the control centre and is transmitted by a low-speed channel to modify the setting each time the system operating conditions change.

Tests to show the likely scheme performance for different loading conditions and for different short circuit levels are presented. Some of the more interesting results are compared with conventional distance relays for solid and resistive faults. These illustrate the advantage offered by implementing such scheme.

The relay which is simulated in software, calculates the line impedance by solving the first order differential line equation. In order to remove the travelling wave distortion and exponentials, analogue and digital filtering techniques are employed.

Results are presented, on a typical 400kV system, for single phase to earth faults and phase to phase faults, where particular emphasis is placed on the effect of short circuit level and fault inception angle. The relay is also tested for closeup faults in the forward and reverse direction. Finally, another method to implement the scheme is introduced and results are presented showing its likely performance.

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

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