ABB Relion 670 Series Applications Manual page 505

1MRK 511 401-UUS F
CT 200/1
Wye
CT 500/5
Wye
ANSI06000558 V1 EN-US
Figure 226: Wye-wye connected power transformer solutions
For this particular power transformer, the 110 kV side phase-to-ground no-load voltages are
exactly in phase with the 36.75 kV side phase-to-ground no-load voltages. Thus, when external
phase angle shift compensation is done by connecting main CTs in delta, both set of CTs must be
identically connected (i.e., either both DAC or both DAB as shown in the right-hand side in
226) in order to put 110 kV & 36.75 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 1 A CT inputs in the IED.
2. Check that LV CTs are connected to 5 A CT inputs in the IED.
3. Make sure that both CT sets are identically connected (i.e., either both side DAC or both side
DAB) when delta connected CTs are used.
4. For wye connected CTs, make sure how they are wye connected (i.e., grounded) towards or
away from the protected transformer.
5. Enter the settings for all three CT input channels used for the HV side CTs as shown in
226.
Table 62: HV side CTs input channels
Setting parameter
CTprim
CTsec
CTStarPoint
Bay control REC670
Application manual
31.5/31.5/(10.5) MVA
110±11×1.5% /36.75/(10.5) kV
YNyn0(d5)
Selected value for solution 1 (wye
connected CT)
200
1
FromObject
© Copyright 2017 ABB. All rights reserved
CT 200/1
in Delta
(DAB)
31.5/31.5/(10.5) MVA
110±11×1.5% /36.75/(10.5) kV
YNyn0(d5)
CT 500/5
in Delta
(DAB)
en06000558_ansi.vsd
Section 17
Monitoring
Figure
Figure
Selected value for solution 2 (delta
connected CT)
200
=
115
3
EQUATION1891 V1 EN-US
(To compensate for delta
connected CTs)
1
ToObject
499