1MAC309294-MB F Section 4
Protection functions
RER620 235
Technical Manual
4.5 Other protection functions available in RER620
4.5.1 Circuit breaker failure protection 50BFT
4.5.1.1 Identification
4.5.1.2 Function block
Figure 106: Function block
4.5.1.3 Functionality
The breaker failure function 50BFT is activated by trip commands from other protection
functions. The commands are either internal commands to the terminal or external
commands through binary inputs. The pickup or start input command can be single phase
or common for all three phases depending on the choice whether single phase or three
phase function is chosen. 50BFT includes a single or all three phase conditional or
unconditional re-trip function, and also back-up trip function.
50BFT uses the same levels of current detection for both re-trip and back-up trip. The
operating values of the current measuring elements can be set within a predefined setting
range. The function has two independent timers for trip purposes: a re-trip timer for the
repeated tripping of its own breaker and a back-up timer for the trip logic operation for
upstream breakers. A minimum trip pulse length can be set independently for the trip
output.
The function contains a blocking functionality. It is possible to block the function outputs,
if desired.
4.5.1.4 Operation principle
The function can be enabled and disabled with the Operation setting. The corresponding
parameter values are Enable and Disable.
The operation of breaker failure protection can be described by using a module diagram in
the figure below, typically for Phase A, when single phase operation mode is selected. All
Function description
IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Circuit breaker failure protection SCCBRBRF 3I>/Io>BF 50BFT
START
TRRET
TRBU
50BFT
BLOCK
POSCLOSE
_A
CB_ FAULT
TRBU_A
POSCLOSE
POSCLOSE
START_
A
TRRET_A
CB_ FAULT_AL
I_B
I_A
I_C
START_
B
START_
C
_B
_C
TRBU_B
TRBU_C
TRRET_B
TRRET_C
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