ABB ret650 - Summary and Conclusions

Setting parameter selected value for both Solution 1
(star conected CT)
Selected value for both
Solution 2 (delta connected
CT)
ConnectTypeW1
Delta (D)
STAR (Y)
1)
ConnectTypeW2 star=y star=y
ClockNumberW2 1 [30 deg lag]
0 [0 deg]
1)
ZSCurrSubtrW1 Off Off
ZSCurrSubtrW2 On
On
2)
TconfigForW1 No No
TconfigForW2 No No
LocationOLTC1 Not Used Not Used
Other parameters Not relevant for this application.
Use default value.
Not relevant for this
application. Use default
value.
1)
To compensate for delta connected CTs.
2)
Zero-sequence current is already removed by connecting main CTs in delta.
6.1.4.4 Summary and conclusions
SEMOD168160-5 v3
The IED can be used for differential protection of three-phase power transformers
with main CTs either star or delta connected. However the IED has been designed
with the assumption that all main CTS are star connected. The IED can be used in
applications where the main CTs are delta connected. For such applications the
following shall be kept in mind:
1. The ratio for delta connected CTs shall be set √(3)=1.732 times smaller than
the actual individual phase CT ratio.
2. The power transformer vector group shall typically be set as Yy0 because the
compensation for power transformer the actual phase shift is provided by the
external delta CT connection.
3. The zero sequence current is eliminated by the main CT delta connections.
Thus on sides where CTs are connected in delta the zero sequence current
elimination shall be set to Off in the IED.
The following table summarizes the most commonly used star-delta vector groups
around the world and provides information about the required type of main CT
delta connection on the star side of the protected transformer.
1MRK 504 169-UEN A Section 6
Differential protection
Transformer protection RET650 2.2 IEC 91
Application manual