GE T35 Instruction Manual page 211
Transformer protection system ur series
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5 SETTINGS
The above diagram shows the physical connections within the transformer that produce a phase angle in the delta winding
that lag the respective wye winding by 30°. The currents in the windings 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 trans-
former terminals ABC respectively. The currents that would be present for a balanced load are shown the diagram below.
Note that the delta winding currents lag the wye winding currents by 30° (in agreement with the transformer nameplate).
Now assume that a source, with a sequence of ACB is connected to transformer terminals A, C, and B, respectively. The
currents present for a balanced load are shown in the Phasors for ACB Phase Sequence diagram.
Note that the delta winding currents leads the wye winding currents by 30°, (which is a type Yd11 in IEC nomenclature and
a type Y/d330 in GE Multilin nomenclature) which is in disagreement with the transformer nameplate. This is because the
physical connections and hence the equations used to calculate current for the delta winding have not changed. The trans-
former nameplate phase relationship information is only correct for a stated phase sequence.
GE Multilin
A
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Figure 5–20: EXAMPLE TRANSFORMER
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Figure 5–21: PHASORS FOR ABC SEQUENCE
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Figure 5–22: PHASORS FOR ACB SEQUENCE
T35 Transformer Protection System
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828716A1.CDR
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828718A1.CDR
5.4 SYSTEM SETUP
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