The neutral point of a 11 kV alternator is earthed through a resistance of 12 ohm. the relay is set to operate when there is out of balance current of 0.8 A. The CTs have a ratio of 200/5. What percentage of the winding is protected against earth faults. What must be the minimum value of earthing resistance required to give 90% of protection to each phase.?

The neutral point of a 11 kV alternator is earthed through a resistance of 12 ohm. the relay is set to operate when there is out of balance current of 0.8 A. The CTs have a ratio of 200/5. What percentage of the winding is protected against earth faults. What must be the minimum value of earthing resistance required to give 90% of protection to each phase.?

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

Chapter7: Symmetrical Faults

Section: Chapter Questions

Problem 7.34P

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