Transients in distance protection

Mathews, P.; Nellist, B.D.

doi:10.1049/piee.1963.0056

Cited by 11 publications

(1 citation statement)

References 4 publications

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“…Time response of relays The polarised-relay characteristics so far given define the range of complex impedances for which the relays instigate circuit-breaker tripping, and the characteristics themselves are those obtaining under threshold conditions. To guard against an incorrect trip on external faults due to errors in impedance measurement caused by time-varying unidirectional transients in the relaying signals, 8 the practice is frequently to lengthen the tripping time as the boundary of the protection characteristic is approached. In this way, the accuracy of impedance measurement by the relays is maintained at the expense of an increased protection measuring time, and speed of response is exchanged for accuracy.…”

Section: Healthy-circuit Relay Encroachmentsmentioning

confidence: 99%

Discriminative performance of distance protection under fault operating conditions

Humpage

Kandil²

1968

Proc. Inst. Electr. Eng. UK

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SynopsisThe paper is devoted to an evaluation in detail of the protection coverage afforded by earth-and phase-fault distance relays in terms of the range of apparent impedances presented to them for which the protection correctly operates and initiates circuit-breaker tripping. This requires a knowledge of both the effective polar characteristics of relays for specified system-fault conditions and also, for the same conditions, the apparent impedance to which the relays respond. Owing to the wide variation encountered in both of these in practice, the ordinary static characteristics of relays provide only a limited indication of the discriminative properties of distance relays in different applications, but it is shown how a comprehensive assessment may be made. In particular, investigations are described of the performance of mho relays when applied to 132kV and 400kV circuits, and the results of the investigations are summarised. The studies include the response to faults within the protected zone, the discrimination against external reverse faults, against healthy-phase relay operation and, on double-circuit-line constructions, the discrimination against healthy-circuit relay operation. The time response of comparators in impedance measurement is introduced, and it is explained how, evolving from this, the coverage afforded by the protection may be directly related to its operating time. In this way a basis is provided on which the operating time of distance relays may be systematically linked to its discriminative properties. List of principal symbols> J Y> h = phase currents VY-. VB = phase voltages Z s \> Zs2 = source impedances in the positive phase sequence at ends ' 1 ' and '2' of the protected circuit, respectively Z L = line impedance in the positive phase sequence so , Z L Q = source and line impedances in the zero phase sequence, respectively S = relaying signal k/_

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Section: Healthy-circuit Relay Encroachmentsmentioning

confidence: 99%