Scheme Communication Logic For Residual Overcurrent Protection (Efc); Application; Functionality; Function Block - ABB REL 501-C1 2.5 Technical Reference Manual

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Scheme communication logic for residual
overcurrent protection (EFC)
Scheme communication logic for residual
overcurrent protection (EFC)

Application

The EFC directional comparison function contains logic for blocking overreaching and permis-
sive overreaching schemes. The function is applicable together with a directional residual over-
current protection in order to decrease the total operate time of a complete scheme.
One communication channel, which can transmit an on / off signal, is required in each direction.
It is recommended to use the complementary additional communication logic EFCA, if the weak
infeed and/or current reversal conditions are expected together with permissive overreaching
scheme.

Functionality

The communication logic for residual overcurrent protection contains logics for blocking over-
reach and permissive overreach schemes.
In the blocking scheme a signal is sent to the remote end of the line if the directional element, in
the directional residual overcurrent protection (sending end), detects the fault in the reverse di-
rection. If no blocking signal is received and the directional element, in the directional residual
overcurrent protection (receiving end), detects the fault in the forward direction, a trip signal will
be sent after a settable time delay.
In the permissive overreach scheme a signal is sent to the remote end of the line if the directional
element, in the directional residual overcurrent protection (sending end), detects the fault in the
forward direction. If an acceleration signal is received and the directional element, in the direc-
tional residual overcurrent protection (receiving end), detects the fault in the forward direction,
a trip signal will be sent, normally with no time delay. In case of risk for fault current reversal
or weak end infeed, an additional logic can be used to take care of this.

Function block

EFC--
EFC
BLOCK TRIP
CACC CS
CSPRM CRL
CSBLK
CR
xx00000204.vsd
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