FUNCTION CHARACTERISTICS
48
NC020 - Manual - 05 - 2022
— Breaker failure - BF
Preface
When the protection issues a trip command but, because an anomaly, the circuit breaker cannot
open, the breaker failure protection issues a back-up trip command to trip adjacent circuit break-
ers.
The breaker failure function is started by internal protective function (if associated with BF).
Operation and settings
The starting of the timer occurs if both the following conditions are filled:
A) Start and trip of internal protective elements (trip of elements matched with BF protection);
B) The CB is closed (the CB state may be acquired by means two binary inputs connected to the
auxiliary contacts 52a and 52b).
The breaker failure protection reliability is improved by means of the CB position control.
If both conditions are held along the set operate time t
BF
, the BF element trips at deadline, vice versa
the timer is cleared and the function is restored.
To the purpose to restore the BF element as quickly as possible, with start of the same protection
(see A condition), additionally to the trip of some internal protections, their starts are required (start
reset is faster than trip reset).
The element may be enabled or disabled by setting the BF Enable parameter (Trip I>, TripI>>...)
available inside the Set \ Profile A(or B) \ Breaker failure-BF menu.
all-FBF.ai
52a/52b
Trip I>
Trip I>>
Trip---
Trip U>>>
Trip BF
BF Enable
t
BF
General logic diagram of the breaker failure element - BF
≥1
Trip int-prot
Fun-BF_Pro-n.ai
TRIPPING MATRIX
(LED+RELAYS)
Trip BF
Trip int-prot
&
&
ON≡
CB Closed
Trip BF
52a
52a
tBF
0T
t
BF
Binary input INx
T 0
Logic
INx
t
ON
INx
t
ON
INx
t
OFF
T0
n.o.
n.c.
INx
t
OFF
52b
Binary input INx
T 0
Logic
INx
t
ON
INx
t
ON
INx
t
OFF
T0
n.o.
n.c.
INx
t
OFF
52b
Logic diagram concerning the breaker failure element -BF
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