A 3-phase, 20 MVA, 11kV star connected alternator is protected by Merz-Price circulating current system. The star point is earthed through a resistance of 5 ohms. If the CTs have a ratio of 1000/5 and the relay is set to operate when there is an out of balance current of 1-5 A, calculate : (i) the percentage of each phase of the stator winding which is unprotected (ii) the minimum value of earthing resistance to protect 90% of the winding [(i) 23-6% (ii) 2-12 ]

A 3-phase, 20 MVA, 11kV star connected alternator is protected by Merz-Price circulating current system. The star point is earthed through a resistance of 5 ohms. If the CTs have a ratio of 1000/5 and the relay is set to operate when there is an out of balance current of 1-5 A, calculate : (i) the percentage of each phase of the stator winding which is unprotected (ii) the minimum value of earthing resistance to protect 90% of the winding [(i) 23-6% (ii) 2-12 ]

Introductory Circuit Analysis (13th Edition)

13th Edition

ISBN:9780133923605

Author:Robert L. Boylestad

Publisher:Robert L. Boylestad

Chapter1: Introduction

Section: Chapter Questions

Problem 1P: Visit your local library (at school or home) and describe the extent to which it provides literature...

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