GE Power Management
745 Transformer Management Relay
5-7
5 SETPOINTS
5.2 AUTO-CONFIGURATION
5
Note that the Delta winding currents lag the Wye winding currents by 30°, which is in agreement with the trans-
former 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 below:
Figure 5–4: PHASORS FOR ACB SEQUENCE
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 Power Management 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 transformer nameplate phase relationship information is
only correct for a stated phase sequence.
It may be suggested that for the ACB sequence the phase relationship can be returned to that shown on the
transformer nameplate by connecting source phases A, B and C to transformer terminals A, C, and B respec-
tively. This will restore the nameplate phase shifts but will cause incorrect identification of phases B and C
within the relay, and is therefore not recommended.
All information presented in this manual is based on connecting the relay phase A, B and C terminals to the
power system phases A, B and C respectively. The transformer types and phase relationships presented are
for a system phase sequence of ABC, in accordance with the standards for power transformers. Users with a
system phase sequence of ACB must determine the transformer type for this sequence.
I
I
I
I
I
I
I
I
I
I
-
-
-
I
I
A
a
b
c
c
l
b
l
a
l
c
l
a
l
b
l
B
C
Summary of Contents for 745 TRANSFORMER MANAGEMENT RELAY
Page 30: ...2 8 745 Transformer Management Relay GE Power Management 2 3 SECURITY 2 GETTING STARTED 2 ...
Page 210: ...7 36 745 Transformer Management Relay GE Power Management 7 2 BLOCK DIAGRAMS 7 SCHEME LOGIC 7 ...
Page 322: ...9 12 745 Transformer Management Relay GE Power Management 9 3 USING 745PC 9 745 PC SOFTWARE 9 ...
Page 396: ...A 4 745 Transformer Management Relay GE Power Management A 1 FIGURES AND TABLES APPENDIXA A ...
Page 400: ...C 2 745 Transformer Management Relay GE Power Management C 1 WARRANTY INFORMATION APPENDIXC C ...
Page 406: ...vi 745 Transformer Management Relay GE Power Management ...
Page 407: ...GE Power Management 745 Transformer Management Relay NOTES ...
