FUNCTION CHARACTERISTICS
39
NA011 - 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 may be 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 one or two binary inputs connected to
the auxiliary contacts 52a and 52b).
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 disabled or enabled by associating to the
BF Enable
parameter the
Trip I>,
trip I>>, trip I>>>, trip IE>, trip IE>>
and
/
or
Trip EXT
parameter.
The
t
BF
and
BF Enable
parameters are available inside the
Set \ Breaker failure-BF
menu.
all-FBF.ai
General logic diagram of the breaker failure element - BF
52b
52a
Trip
Star t BF
Trip BF
BF Enable
t
BF