Current transformers of current ratio of 1000/5 A are used for protection of a star connected 3 phase, 10 MVA, 6.6 kV alternator. If the relay is set to operates for a minimum current of 0.5 A, Calculate the percentage of each phase stator winding which is unprotected agains earth fault when the machine operates at normal voltage. Assume that star point of alternator is earthed through a resistance of 7.5 2.

Current transformers of current ratio of 1000/5 A are used for protection of a star connected 3 phase, 10 MVA, 6.6 kV alternator. If the relay is set to operates for a minimum current of 0.5 A, Calculate the percentage of each phase stator winding which is unprotected agains earth fault when the machine operates at normal voltage. Assume that star point of alternator is earthed through a resistance of 7.5 2.

Power System Analysis and Design (MindTap Course List)

6th Edition

ISBN:9781305632134

Author:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Publisher:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Chapter3: Power Transformers

Section: Chapter Questions

Problem 3.56P: Three single-phase two-winding transformers, each rated 3kVA,220/110volts,60Hz, with a 0.10 per-unit...

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