REG 316*4 1MRB520049-Uen / Rev. F ABB Switzerland Ltd
3-289
Tripping delay tEFP
The setting for tEFP can be seen from Fig. 3.5.28.2 which shows
a typical timing diagram for tripping a fault.
CB
open (3)
EFP
tripping signal (4)
tEFP
CB
tripping signal (1)
t
CB open
CB
tripped (2)
t
Reset
+ t
Margin
t
CB Off
Fig. 3.5.28.2 Timing diagram for an end zone fault
(1) Tripping command applied to the CB.
(2) CB auxiliary contact sends a signal that the CB is open to
the “CB Off” input of the function which is used to start the
EFP.
(3) The circuit-breaker ruptures the fault current.
(4) After a reset delay plus a safety margin, the current unit ei-
ther detects that the fault current has been interrupted and
the EFP function resets, or the fault current continues to
flow and an EFP signal is issued.
ResetOffCBopenCB
ttttEFP +-³ + t
Margin
t
CB open
CB opening time including arc extinction time
t
CB Off
CB opening time of the CB auxiliary contact
(Signal „CB open“)
t
Reset
Reset time of the current detector
3)
t
Margin
Allowance for variations in normal fault clearing time
4)
3)
see reset time of the current detector t
Reset
4)
see Margin time t
Margin
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