Distance Digital Algorithm Immune to Saturation of Current Transformer
Wiszniewski, A (Wroclaw University of Technology, Poland) ; Szafran, J (Wroclaw University of Technology, Poland)
/ ||I08/1989/I-044 ||ENY-ARTICLE-2008-206|
Abstract: Saturation of current transformers due to slowly decaying primary current D.C. components cause errors in reproduction of the current fundamental harmonic. Most of the relays are more or less sensitive to the errors. If the saturation occures before the given relay operated. the operation may be delayed up to about 2 time constants of the D.C.component. In some, although rare cases, transient CT errors may cause unselective operation of the relay. Whether the current transformer saturates and when it occures depend mainly on the accuracy limit factor and on the residual flux in the transformer core. However bearing in mind the very high expected values of short circuit currents and the long D.C. time constants one may conclude, that the design of CT-s which never saturate would end in bulky and expensive units. Therefore most of the protective CT-s which are in service saturate during severe transients. It is a duty of protection engineers to design the relays in such a way, that the errors caused by the saturation neither cause maloperation, nor bring about excessive delay.
Keyword(s): distance protection ; current transformer
Note: Developments in power system protection. Fourth International Conference, London, 11-13 April 1989. London : IEE, 1989. pp. 196-199
Fulltext : http://zet10.ipee.pwr.wroc.pl/record/260/files/
Cited by: try citation search for ENY-ARTICLE-2008-206; I08/1989/I-044
Record created 2008-11-11, last modified 2008-11-11
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