ABB REG670 Applications Manual

To compensate for delta connected CTs, see equation 20.
7. Enter the following values for the general settings of the differential protection
function, see table 22
Table 22: General settings of the differential protection function
Setting parameter
Selected value for both Solution 1
(star connected)
Selected value for both Solution 2
(delta connected)
RatedVoltageW1 110 kV 110 kV
RatedVoltageW2 36.75 kV 36.75 kV
RatedCurrentW1 165 A 165 A
RatedCurrentW2 495 A 495 A
ConnectTypeW1 STAR (Y) STAR (Y)
ConnectTypeW2 star=y star=y
ClockNumberW2 0 [0 deg] 0 [0 deg]
ZSCurrSubtrW1 On
Off
1)
ZSCurrSubtrW2 On
Off
1)
TconfigForW1 No No
TconfigForW2 No No
LocationOLT1 Winding 1 (W1) Winding 1 (W1)
LowTapPosOLTC1 1 1
RatedTapOLTC1 12 12
HighTapPsOLTC1 23 23
TapHighVoltTC1 23 23
StepSizeOLTC1 1.5% 1.5%
Other parameters Not relevant for this application.
Use default value.
Not relevant for this application.
Use default value.
1)
Zero-sequence current is already removed by connecting main CTs in delta.
7.1.4.4 Summary and conclusions
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.
Section 7 1MRK 502 071-UEN -
Differential protection
146 Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual

ABB REG670 Specifications

General

Brand	ABB
Model	REG670
Category	Protection Device
Language	English