Basler BE1-CDS220, Instruction Manual

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D-14 Settings Calculations BE1-CDS220
Figure D-7 illustrates how a lower Rs value reduces the difference between SF and SF’.
Figure D-7. Reducing the Difference between SF and SF’
Conclusion
This analysis shows that the easy to apply SF based on the ANSI Accuracy Class may yield optimistic
results in cases where the CT internal resistance is significant. The Excitation Curve method, requiring
more data, yields more accurate results and should be used when the SF is marginal.
SETTING NOTE 2 - CT BURDEN, DELTA CONNECTED CT’S, 3-PHASE FAULT
B
A
D2857-22.vsd
11-09-99
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- I
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RELAY
Figure D-8. CT Burden, Delta Connected CTs, 3-Phase Fault
SF
IF
SF'
IF
IF
0 20 40 60 80 100
0
0.2
0.4
SF and SF` for Zc=2, ZB=0.5, Rs=0.2