Page 50 - Electrical Equipment Handbook _ Troubleshooting and Maintenance

TRANSFORMERS

TRANSFORMERS 3.7

FIGURE 3.4 The power system of Example 3.1 (a) without and (b) with transformers at the ends of the
transmission line.

a. Eliminate transformer T by referring the load over to the transmission line’s volt-
2
age level.
b. Eliminate transformer T by referring the transmission line’s elements and the
1
equivalent load at the transmission line’s voltage over to the source side.
The value of the load’s impedance when reflected to the transmission system’s volt-
age is
2
Z' a Z
load load
2
10
(4 j3 )
1
400 j300
The total impedance at the transmission line level is now
Z Z Z'
eq line load
400.18 j300.24 500.3 36.88°
This equivalent circuit is shown in Fig. 3.5a. The total impedance at the transmission
line level (Z Z' ) is now reflected in across T source’s voltage level:
line load 1
2
Z' a Z
eq eq
2
a (Z Z' )
line load
2
( ⁄10) [(0.18 j0.24) (400 j300)]
1
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