GE 845 Instruction Manual page 197

CHAPTER 4: SETPOINTS
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
Figure 4-37: Example Transformer
The Example Transformer figure shows the physical connections within the transformer
that produce a phase angle in the delta winding lagging the respective wye winding by
30°. The winding currents are also identified. Note that the total current out of the delta
winding is described by an equation. Now assume that a source, with a sequence of ABC, is
connected to transformer terminals ABC, respectively. The currents that would be present
for a balanced load are shown below.
Figure 4-38: Phasors for ABC Sequence
Note that the delta winding currents lag the wye winding currents by 30°, which is in
agreement with the transformer nameplate.
Now assume that a source, with a sequence of ACB is connected to transformer terminals
A, C, B respectively. The currents that would be present for a balanced load are shown in
the next figure: Phasors for ACB Sequence.
Figure 4-39: Phasors for ACB Sequence
h f
SYSTEM
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