When a protective current transformer (CT) operates in a reclosing process, the core will contain a certain amount of residual flux, which cannot be significantly reduced during reclosure. If a later fault occurs after reclosing, the CT core will rapidly saturate, resulting in protection devices refusing to operate or mal-operating. Aiming at this problem, a fast CT demagnetization strategy under reclosing process is proposed in this paper. The proposed demagnetization strategy is achieved by a demagnetizing circuit connected to the CT secondary side, which can generates a time varying voltage to control the CT magnetic flux. Different from the traditional demagnetization method, the proposed demagnetization strategy can be used for the already in-service CTs. Finally, simulations are carried out to verify the effectiveness of the proposed method under the reclosing process, and from the results, the method can operate faster and more efficiently. Furthermore, the selection methods of DC voltage source and current-limiting resistance in demagnetizing circuit is introduced in this paper.
Residual flux suppression of protective current transformers for autoreclosure process
01.08.2017
747496 byte
Aufsatz (Konferenz)
Elektronische Ressource
Englisch
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