sepam 20 user manual - Schneider Electric

3
Protection functions Breaker failure
ANSI code 50BF
3/24
DE80107
Operation
This function is designed to detect when a breaker fails, i.e. when it fails to open when
a trip order is sent.
The "breaker failure" function is activated:
b by a trip order issued by the overcurrent protection functions
(50/51, 50N/51N, 46)
b by an external trip order sent by logic input I24 (I24 should be assigned to external
trip function 5)
It checks that the current has disappeared within the time interval specified by time
delay T. It can also take account of the position of the breaker read on the logic inputs
to determine effective breaker opening.
When the circuit breaker control function is used, the breaker failure function is
activated automatically by protection units 50/51, 50N/51N and 46, which trip the
breaker.
When the circuit breaker control function is not used, the user has the choice of
overcurrent protection functions to associate with the breaker failure protection
function.
The protection delayed output should be assigned to a logic output using the control
matrix.
Launching and stopping the time delay counter T both depend on the presence of a
current above the set point (I > Is) or, according to the parameter setting, on the
absence of breaker opening.
Block diagram
(I24) external tripping 5
Note: When an external trip order is issued on input I24 of an MES114 module configured for AC,
the 50BF operating characteristics are not guaranteed.
PCRED301005EN - 06/2008