The figure above shows the percentage differential relay used for the protection of an alternator winding. The relay has a minimum pick up current of 0.2 ampere and has a percentage slope of 10%. A high resistance ground fault occurs near the grounded neutral end of the generator winding with the current distribution as shown. Assume a CT ratio of 400: 5; determine whether the relay will operate.

The figure above shows the percentage differential relay used for the protection of an alternator winding. The relay has a minimum pick up current of 0.2 ampere and has a percentage slope of 10%. A high resistance ground fault occurs near the grounded neutral end of the generator winding with the current distribution as shown. Assume a CT ratio of 400: 5; determine whether the relay will operate.

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

Chapter12: Power System Controls

Section: Chapter Questions

Problem 12.4P

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Concept explainers

Synchronous Motor

The synchronous motor is an AC electric type motor where at a steady-state the shaft rotation is synchronized with the supply current variable-frequency. To an integral number of AC cycles, the rotation period is exactly equal. The stator of the motor in the synchronous motor contains multi-phase AC electromagnets due to which a magnetic field is created that rotates in time with the oscillation of the line current. The rotor contains a permanent magnet and the rotor rotates in synchronization with the stator field at the same rate and provides the second synchronized magnetic field which is rotating in nature as a result. When the synchronous motor is supplied with independently excited multi-phase AC electromagnets on both the rotor and the stator, it is termed as a doubly-fed machine. The most widely used AC-type motors are the synchronous AC motor and the induction AC motors.

Question

The figure above shows the percentage differential relay used for the
protection of an alternator winding. The relay has a minimum pick up current of 0.2 ampere
and has a percentage slope of 10%. A high resistance ground fault occurs near the grounded
neutral end of the generator winding with the current distribution as shown. Assume a CT
ratio of 400: 5; determine whether the relay will operate.

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