Example 3.2Using the transformer equivalent circuit found in Example 3.1, determine the line-to-neutral (120 V)and line-to-line (240 V) fault currents in three-wire single-phase 120/240 V secondaries shown inFigures 3.33 and 3.34, respectively. In the figures, R represents the resistance of service-drop cableper conductor. Usually R is much larger than X for such cable and therefore X may be neglected.Using the given dala, determine the following:a. Find the symmetrical rms fault currents in the HV and LV circuits for a 120 V fault if R of theservice-drop cable is zero.b. Find the symmetrical rms fault currents in the HV and LV circuits for a 240 V fault if R of theservice-drop cable is zero.c. If the transformer is a CSPB type, find the minimum allowable interrupting capacity (in sym-metrical rms amperes) for a circuit breaker connected to the transformer's LV terminals.24.637 L 53.9 28.525 x 10 L 18.9 nH(x)ISHV120 V7200 VX2120 Vx3H28.525 x 10-3 L 18.9° 0R> Relehelelelllllll

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Answered: determine the line-to-neutral (120 V)

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Electrical Engineering

determine the line-to-neutral (120 V)

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 3.64P: The per-unit equivalent circuit of two transformers Ta and Tb connected in parallel, with the same...

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Single Phase AC Circuit

Alternating Current (AC) is a type of electric power in which the electric current changes, both in magnitude and direction, at regular intervals. This AC Circuits can deliver power in either a Single Phase system or a Three Phase system.

Question

Example 3.2
Using the transformer equivalent circuit found in Example 3.1, determine the line-to-neutral (120 V)
and line-to-line (240 V) fault currents in three-wire single-phase 120/240 V secondaries shown in
Figures 3.33 and 3.34, respectively. In the figures, R represents the resistance of service-drop cable
per conductor. Usually R is much larger than X for such cable and therefore X may be neglected.
Using the given dala, determine the following:
a. Find the symmetrical rms fault currents in the HV and LV circuits for a 120 V fault if R of the
service-drop cable is zero.
b. Find the symmetrical rms fault currents in the HV and LV circuits for a 240 V fault if R of the
service-drop cable is zero.
c. If the transformer is a CSPB type, find the minimum allowable interrupting capacity (in sym-
metrical rms amperes) for a circuit breaker connected to the transformer's LV terminals.
24.637 L 53.9 2
8.525 x 10 L 18.9 n
H
(x)
ISHV
120 V
7200 V
X2
120 V
x3
H2
8.525 x 10-3 L 18.9° 0
R> R
elehele
lelllllll

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