For wye connected main CTs, the main CT ratio shall be set as it is in actual
application. The “W
yePoint” parameter, for the particular wye connection shown in
figure
53, shall be set ToObject. If wye connected main CT
s have their wye point away
from the protected transformer this parameter should be set FromObject.
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)
• 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 “WyePoint” 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
53.
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)
• 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 “WyePoint” 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
53.
For more detailed info regarding CT data settings please refer to the three application
examples presented in section "Application Examples".
7.1.4.3 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 wye connected.
• Second solution will be with delta connected main CT on Y (that is, wye)
connected sides of the protected power transformer.
For each differential protection solution the following settings will be given:
1MRK 502 071-UUS A Section 7
Differential protection
Generator protection REG670 2.2 ANSI and Injection equipment REX060, REX061, REX062 145
Application manual
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