ABB Relion 670 Series Applications Manual page 501

1MRK 511 401-UUS F
• Solution 1: with all main CTs wye connected
• Solution 2: with delta connected main CT on Y (i.e., wye) connected sides of the protected
power transformer
The following settings are given for each solution:
• Input CT channels on the transformer input modules
• General settings for the transformer through fault monitoring where specific data about
monitored power transformer is entered.
Example 1: Wye-delta connected power transformer without on-load tap changer
Single line diagrams for two possible solutions for such type of power transformer with all
relevant application data is given in
CT 300/5
20.9 MVA
69/12.5 kV
YNd1
(YD )
AC
CT 800/5
Wye
ANSI06000554 V1 EN-US
Figure 224: Wye-delta connected power transformer solutions
For this particular power transformer, the 69 kV side phase-to-ground no-load voltages lead the
12.5 kV side phase-to-ground no-load voltages by 30 degrees. Thus, ensure that the HV currents
are rotated by 30° in the clockwise direction when external phase angle shift compensation is
done by connecting main HV CTs in delta (as shown in
DAC delta CT connection must be used for 69 kV CTs in order to put 69 kV & 12.5 kV currents in
phase.
In order to ensure proper application of the IED for this power transformer, proceed as follows:
Bay control REC670
Application manual
Wye
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Figure 224.
CT 300/5
in Delta
(DAC)
20.9 MVA
69/12.5 kV
YNd1
(YD )
AC
CT 800/5
Wye
Figure
GUID-10200B25-5D36-4BB3-8095-B5313C8E1D30 v1
en06000554_ansi.vsd
224, right-hand side). Therefore, the
Section 17
Monitoring
495