ABB ret650 - Page 96

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 LV delta connected CTs are DAB connected.
3. For star connected CTs make sure how they are 'star'red (that is, earthed) to/from
protected transformer.
4. Enter the following settings for all three CT input channels used for the HV side
CTs, see table
13.
Table 13: CT input channels used for the HV side CTs
Setting parameter Selected value for both solutions
CTprim 400
CTsec 5
CTStarPoint ToObject
5. Enter the following settings for all three CT input channels used for the LV side
CTs, see table "CT input channels used for the LV side CTs".
CT input channels used for the LV side CTs
Setting parameter
Selected value for Solution 1 (star
connected CT)
Selected value for Solution 2
(delta connected CT)
CTprim 1500
1500
866
3
=
EQUATION1889 V1 EN-US (Equation 13)
CTsec
5 5
CTStarPoint ToObject ToObject
To compensate for delta connected CTs, see equation 13.
6. Enter the following values for the general settings of the differential protection
function, see table
14.
Table 14: General settings of the differential protection
Setting parameter
selected value for both Solution 1
(star conected CT)
Selected value for both
Solution 2 (delta connected
CT)
RatedVoltageW1
115 kV 115 kV
Rated VoltageW2 24.9 kV 24.9 kV
RatedCurrentW1 301 A 301 A
RatedCurrentW2 1391 A 1391 A
Table continues on next page
Section 6 1MRK 504 169-UEN A
Differential protection
90 Transformer protection RET650 2.2 IEC
Application manual