REG 316*4 1MRB520049-Uen / Rev. B ABB Switzerland Ltd
4-43
Ext Trip t2
Ext Trip EFP
Start Ext
CB On
CB Off
Unconditional
logic
End Fault
logic
Retrip
logic
Redundant
logic
Back up logic
Remote logic
Current
detectors
Start Lx
I
Red Trip Lx
Trip t1 Lx
Retrip t1
Remote Trip
Backup Trip t2
EFP Bus Trip
EFS Rem Trip
Uncon Trip t2
Uncon Trip t1
Ext Trip t1
Trip t2
Trip t1
HEST 005 045 C
³
1
³
1
³
1
Fig. 4.19 Block diagram
4.2.7.2. Three-phase/ single-phase mode
The function has three current detectors. When it is used in the
three-phase mode, each current detector measures the current
in each of the three phases.
In order to accommodate a fourth current detector measuring the
neutral current, this function has to be duplicated and the second
function set to the single-phase mode and the appropriate cur-
rent pick-up. The two functions then operate in parallel .
This arrangement also covers the two special cases of phase-to-
phase-to-ground and three-phase-to-ground faults.
4.2.7.3. ‘Redundant Trip’
The ‘Redundant Trip’ logic performs phase-segregated direct
tripping of the same circuit-breaker without any intentional time
delay, if the Start inputs are active and the corresponding current
detectors have picked up. This ensures that the breaker receives
a tripping command in the event of a unit protection trip circuit
failure, which would otherwise cause a second attempt to trip the
same breaker or backup tripping of the surrounding breakers.
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