ANSI05000164 V1 EN-US
Figure 58: Example for the high impedance restricted earth fault protection
application
For a through fault one current transformer might saturate when the other CTs still will
feed current. For such a case a voltage will be developed across the measuring branch.
The calculations are made with the worst situations in mind and a minimum operating
voltage V
R
is calculated according to equation
18
EQUATION1531-ANSI V1 EN-US (Equation 18)
where:
IF
max is the maximum through fault current at the secondary side of the CT
Rct
is the current transformer secondary winding resistance and
Rl
is the maximum loop resistance of the circuit at any CT.
1MRK 502 071-UUS A Section 7
Differential protection
Generator protection REG670 2.2 ANSI and Injection equipment REX060, REX061, REX062 159
Application manual
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