J.C. Yang, X.G. Yin, D.S. Chen, and Z. Zhang
Sampled value-differential protection, short transmission line,phasor-differential protection, current transformer (CT) saturation
This article describes the principle of sampled value-differential protection and discusses the selections of S and R values in the protection of short transmission lines. The basic selective rule is to ensure the restraint effectiveness of sampled value-differential protection equal or superior to the corresponding phasor-differential protection during external faults. Investigation shows the proposed method’s ability to avoid CT saturation and bad data is superior to that of the phasor methods. A new short transmission line protection system based on the proposed protection has been developed for GeZhouBa Hydroelectric Power Plant. Test results in the Electrical Power Dynamic Laboratory (EPDL) verify the protection performance. This system is now being put into trial operation.
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