ABB ret650, Applications Manual

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• are increased √3 times (1.732 times) in comparison with star connected CTs
• lag by 30° the primary winding currents (this CT connection rotates currents
by 30° in clockwise direction)
• do not contain zero sequence current component
For DAC delta connected main CTs, ratio shall be set for √3 times smaller than the
actual ratio of individual phase CTs. The “StarPoint” parameter, for this particular
connection shall be set
ToObject . It shall be noted that delta DAC connected main
CTs must be connected exactly as shown in figure 31 .
For delta DAB connected main CTs, secondary currents fed to the IED:
• are increased √3 times (1.732 times) in comparison with star connected CTs
• lead by 30° the primary winding currents (this CT connection rotates currents
by 30° in anti-clockwise direction)
• do not contain zero sequence current component
For DAB delta connected main CT ratio shall be set for √3 times smaller in RET
670 then the actual ratio of individual phase CTs. The “StarPoint” parameter, for
this particular connection shall be set
ToObject . It shall be noted that delta DAB
connected main CTs must be connected exactly as shown in figure 31 .
For more detailed info regarding CT data settings please refer to the three
application examples presented in section
"Application Examples" .
6.1.4.3 Application Examples
SEMOD167854-5 v2
Three application examples will be given here. For each example two differential
protection solutions will be presented:
• First solution will be with all main CTs star connected.
• Second solution will be with delta connected main CT on Y (that is, star)
connected sides of the protected power transformer.
For each differential protection solution the following settings will be given:
1. Input CT channels on the transformer input modules.
2. General settings for the transformer differential protection where specific data
about protected power transformer shall be entered.
Finally the setting for the differential protection characteristic will be given for all
presented applications.
Example 1: Star-delta connected power transformer without on-load
tap-changer
SEMOD167854-110 v5
Single line diagrams for two possible solutions for such type of power transformer
with all relevant application data are given in figure
32 .
Section 6
1MRK 504 169-UEN A
Differential protection
86 Transformer protection RET650 2.2 IEC
Application manual