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6 F 2 S 0 8 5 7
• Apply an infeed current to terminal TB1-1 and -2.
When the infeed current applied is larger than the setting of ik (pu) and smaller than [kp
⋅p2 +
(1
−p1)ik]/(p2 − p1) (pu), characteristic DF1 is checked.
When the infeed current applied is larger than [kp
⋅p2 + (1−p1)ik]/(p2 − p1) (pu), characteristic
DF2 is checked.
Note: When the default settings are applied, the critical infeed current which
determines DF1 checking or DF2 checking is 1.6×(CT secondary rated
current).
• Apply an outflow current of the same magnitude and counterphase with the infeed current, to
terminal TB1-7 and -8.
• Decrease the outflow current in magnitude and measure the values at which the element
operates.
• Check that the measured values are within 15% of the theoretical values.
For characteristic DF1, the theoretical outflow current is given by the following equation.
I
out
= (1−p
1
)(I
in
−ik) (pu)
where,
p1 = slope setting of DF1 (= 0.1 fixed)
ik = minimum operating current setting
When the default settings are applied, I
out
= 0.9× (I
in
– 0.5) × (CT secondary rated current). For
characteristic DF2, the theoretical outflow current is given by the following equation
I
out
= (1−p
2
) I
in
+ p
2
×kp (pu)
where,
p
2
= slope setting of DF2
kp = restraining current section setting of DF2
When the default settings are applied, I
out
= 1.0 × (CT secondary rated current).