A 3-phase, 10 MVA, 11 kV generator with a solidly earthed neutral point supplies a feeder. The relevant impedances of the generator and feeder in ohms are as under: Positive sequence impedance Negative sequence impedance Zero sequence impedance Generator j 1.2 j 0.9 j0.4 feeder j 1.0 j 1.0 j 3.0

A 3-phase, 10 MVA, 11 kV generator with a solidly earthed neutral point supplies a feeder. The relevant impedances of the generator and feeder in ohms are as under: Positive sequence impedance Negative sequence impedance Zero sequence impedance Generator j 1.2 j 0.9 j0.4 feeder j 1.0 j 1.0 j 3.0

Introductory Circuit Analysis (13th Edition)

13th Edition

ISBN:9780133923605

Author:Robert L. Boylestad

Publisher:Robert L. Boylestad

Chapter1: Introduction

Section: Chapter Questions

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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

A 3-phase, 10 MVA, 11 kV generator with a solidly earthed neutral point
supplies a feeder. The relevant impedances of the generator and feeder in ohms are as under :
feeder
j 1.0
j 1.0
j 3-0
Positive sequence impedance
Negative sequence impedance
Zero sequence impedance
Generator
j 1-2
j 0.9
j0.4

roor
B
N
R
elle
EB
TER
mor
Y
IR
ly = 0
IB=0
If a fault from one phase to earth occurs on the far end of the feeder, calculate
(i) the magnitude of fault current

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