ABB Relion 670 Series Applications Manual page 503

1MRK 511 401-UUS F
CT 400/5
60 MVA
115/24.9 kV
Dyn1
(D Y)
AB
CT 1500/5
ANSI06000555 V1 EN-US
Figure 225: Delta-wye connected power transformer solutions
For this particular power transformer, the 115 kV side phase-to-ground no-load voltages lead the
24.9 kV side phase-to-ground no-load voltages by 30 degrees. Thus, ensure that the 24.9 kV
currents are rotated by 30° in the anti-clockwise direction when external phase angle shift
compensation is done by connecting main 24.9 kV CTs in delta (as shown in
side). Therefore, the DAB CT connection must be used for 24.9 kV CTs in order to put 115 kV & 24.9
kV currents in phase.
In order to ensure proper application of the IED for this power transformer, proceed as follows:
1. Ensure that HV & LV CTs are connected to 5 A CT inputs in the IED.
2. For the second solution, make sure that LV delta connected CTs are DAB connected.
3. For wye connected CTs, make sure how they are wye connected (i.e., grounded) to/from the
protected transformer.
4. Enter the settings for all three CT input channels used for the HV side CTs as shown in
59.
Table 59: HV side CTs input channels
Setting parameter
CTprim
CTsec
CTStarPoint
Bay control REC670
Application manual
Wye
Wye
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CT 400/5
Wye
60 MVA
115/24.9 kV
Dyn1
(D Y)
AB
CT 1500/5
in Delta
(DAB)
en06000555_ansi.vsd
Selected value for both solutions
400
5
ToObject
Section 17
Monitoring
Figure 225, right-hand
Table
497