ABB Relion 670 Series Applications Manual page 526
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- Technical manual (1432 pages) ,
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Section 18
Monitoring
For DAC delta connected main CTs, the ratio shall be set for √3 times smaller than the actual
ratio of individual phase CTs. The
be set as
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)
•
Does not contain zero sequence current component and consequently winding currents
are not properly measured for all types of faults
For DAB delta connected, main CT ratio shall be set √3 times smaller than the actual ratio of
individual phase CTs. The
ToObject .
For more detailed information regarding CT data settings, refer to Section
examples.
18.12.4.2
Application examples for power transformers
Three application examples are presented here and each one has the following solutions:
•
Solution 1: with all main CTs star connected
•
Solution 2: with delta connected main CT on Y (i.e., star) connected sides of the protected
power transformer
The following settings are given for each solution:
•
Input CT channels on the transformer input modules
•
General settings for the transformer through fault monitoring where specific data about
monitored power transformer is entered.
Example 1: Star-delta connected power transformer without on-load tap changer
Single line diagrams for two possible solutions for such type of power transformer with all
relevant application data is given in
520
ToObject .
The delta DAC connected main CTs must be connected exactly as shown in
Figure
252.
StarPoint parameter for this particular connection shall be set as
The delta DAB connected main CTs must be connected exactly as shown in
Figure
252.
It is strongly recommended to use star connected main CTs on all sides of the
monitored power transformer.
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StarPoint parameter, for the particular star connection shall
Figure
253.
1MRK 511 401-UEN Rev. K
Application
GUID-694949AA-4EA8-4B30-B8D1-10AB0A7622A7 v1
GUID-10200B25-5D36-4BB3-8095-B5313C8E1D30 v1
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