New phase selection techniques for single-pole-autoreclosure schemes employing directional comparison protection.

  • Mahmoud Mohy El-Din Mahmoud

Student thesis: Doctoral ThesisPhD


The success of single pole autoreclosure relies on correct selection of the faulted phase and hence on the ability of the phase selectors to perform this task. In this thesis novel techniques which provide UHS phase selection have been developed. The lattice method was used to assist with the early development of the algorithm, in order to determine the approximate response of the modal variations of a 3-phase lossless system. The algorithm, in terms of primary system variations, was then tested using established digital techniques for modelling the faulted response of any arbitrary linear shunt reactor compensated EHV feeder system. The technique was then implemented within secondary simulation programs to indicate any susceptibility to transducers and digital processing errors. The new phase selector provides satisfactory phase discrimination following very high resistance faults and caters for evolving fault conditions. An evaluation of the performance of the new scheme for different line and source configurations is reported. The simulation results show the phase selector to have very good selective properties, complemented with very high speed of operation. The scheme, in a typical application such as that considered, has an operating time of 2 to 5ms for most fault conditions. Some insight is given into the techniques necessary for the opening of only one pole for clearance of both single phase to ground faults and interphase faults clear of ground, and the necessary modifications to the basic phase selector scheme are proposed. The investigation also presents the results of computer evaluations of the discriminative properties of the new scheme under complete fault clearance sequences. The performance of the phase selection equipment during single pole and three pole autoreclosure sequences is reported. The thesis concludes by presenting the results of preliminary field tests which go some way towards validating the aforementioned novel phase selection techniques developed.
Date of Award1984
Original languageEnglish
Awarding Institution
  • University of Bath

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