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108
Two step definite and inverse time-
delayed residual
overcurrent protection (TEF1 and TEF2)
The switch-onto-fault function is used to minimize the operate time in case of pole dis-
crepancy at breaker closing and in case of closing on to a fault. The function is released
by activating the TEF1--BC binary input and will operate if I
IN>Low during 300 ms. The function is activated for 1 second after the reset of the
TEF1--BC binary input.
The residual overcurrent function is blocked by activating the TEF1-BLOCK binary in-
put.
Activating the TEF1-BLKTRLS blocks the low current definite/inverse delay trip out-
puts TEF1-TRLS and the switch-on-to-fault trip TEF1-TRSOTF.
The I
current lags the polarizing voltage (U
N
the zero-sequence source impedance. The forward measuring element (STFW) operates
when:
⋅
(
ϕ
65 °
) IN>Dir
≥
I
cos
–
N
where:
ϕ
is the angle between I
IN>Dir
is the set operate value
) by a phase angle equal to the angle of
N
and U
(positive if I
lags U
N
N
N
&KDSWHU
&XUUHQW
is equal or greater than
N
(Equation 51)
) and
N
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