ABB Relion 670 Series Applications Manual page 500

Section 17
Monitoring
For wye connected main CTs, secondary currents fed to the IED:
• Are directly proportional to the measured primary currents
• Are in phase with the measured primary currents
• Contains all sequence components including zero sequence current component
For wye connected main CTs, the main CT ratio shall be set as it is in the actual application. The
StarPoint parameter, for the particular wye connection shown in
ToObject . If wye connected main CTs have their wye point away from the protected transformer,
this parameter shall be set as
For delta DAC connected main CTs, secondary currents fed to the IED:
• Are increased √3 times (1.732 times) in comparison with wye connected CTs
• Lag by 30° the primary winding currents (this CT connection rotates currents by 30° in
clockwise direction)
• Does not contain zero sequence current component and consequently winding currents are
not properly measured for all types of faults
For DAC delta connected main CTs, the ratio shall be set for √3 times smaller than the actual ratio
of individual phase CTs. The
ToObject .
For delta DAB connected main CTs, secondary currents fed to the IED:
• Are increased √3 times (1.732 times) in comparison with wye 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
17.12.4.2 Application examples for power transformers
Three application examples are presented here and each one has the following solutions:
494
FromObject .
StarPoint parameter, for the particular wye connection shall be set as
The delta DAC connected main CTs must be connected exactly as shown in
223.
StarPoint parameter for this particular connection shall be set as
The delta DAB connected main CTs must be connected exactly as shown in
223.
It is strongly recommended to use wye connected main CTs on all sides of the
monitored power transformer.
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1MRK 511 401-UUS F
Figure 223, shall be set as
Application examples.
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Bay control REC670
Application manual
Figure
Figure