ABB RELION RET670 Applications Manual page 155

1MRK 504 163-UUS A
Transformer protection RET670 2.2 ANSI
Application manual
are rotated by 30° in clockwise direction. Thus the DAC delta CT connection must be
used for 69 kV CTs in order to put 69 kV & 12.5 kV currents in phase.
To ensure proper application of the IED for this power transformer it is necessary to do
the following:
1. Check that HV & LV CTs are connected to 5 A CT inputs in the IED.
2. For second solution make sure that HV delta connected CTs are DAC connected.
3. For wye connected CTs make sure how they are stared (that is, grounded) to/from
protected transformer.
4. Enter the following settings for all three CT input channels used for the LV side CTs
see table 15.
Table 15: CT input channels used for the LV side CTs
Setting parameter Selected value for both solutions
CTprim
CTsec
CT_WyePoint
5. Enter the following settings for all three CT input channels used for the HV side
CTs, see table 16.
Table 16: CT input channels used for the HV side CTs
Setting parameter
CTprim
CTsec
CT_WyePoint
To compensate for delta connected CTs, see equation 14.
6. Enter the following values for the general settings of the Transformer differential
protection function, see table 17.
800
5
ToObject
Selected value for solution 1 (wye
connected CT)
300
5
From Object
Section 7
Differential protection
Selected value for solution 2 (delta
connected CT)
300
=
173
3
(Equation 14)
EQUATION1888 V1 EN-US
5
ToObject
149