50BF Circuit-Breaker Failure Protection – 3 Pole
Overview of Functions
Where a circuit‑breaker (CB) fails to operate, the power system will remain in a hazardous state until current
flow is interrupted by remote or back-up protections. To minimize any delay, CB failure protection monitors
the status and tripping of the associated CB and issues a back-up trip signal if the CB fails.
Structure of the Function
The circuit-breaker fail function element has group dependent settings. These settings can be different in each
settings group – group numbers (Gn) 1 to 4.
This function corresponds to the logical node
A50BFRBRF*
in IEC 61850.
The function monitors the primary system using the 4 current inputs e.g. CT1/2/3/4. The fundamental
frequency component is measured from processing of the measured current samples.
The function is initiated by the operation of output relays assigned as trip contacts or from a binary input.
Current flow is monitored after a tripping signal has been issued. If any of the 50BF current check elements
have not reset before the timers have expired an output is given. For CB trips where the fault is not current
related an additional input is provided,
50BF Mech Trip
, which monitors the CB closed input and provides
an output if the circuit‑breaker has not opened before the timers expire.
Outputs are also given to indicate the faulted phase, 50BF PhA , 50BF PhB, 50BF PhC and 50BF EF.
The circuit-breaker fail function has 2 time delayed outputs. For some systems, only the first will be used and
the CB failure output will be used to back-trip the adjacent CB(s). On other systems, however, this output will
be used to re-trip the local CB to minimize potential disruption to the system, if possible via a secondary trip
coil and wiring. The second CB failure stage will then be used to back-trip the adjacent CB(s). The 2 time delays
run concurrently.
The circuit-breaker fail protection time delays are initiated either from:
•
An output trip contact of the relay (
Configuration > Binary Outputs > Trip Config > Trip
Contacts
), or
•
A binary or virtual input assigned to
50BF Ext Trip
(
Configuration > Binary Inputs >
Input Matrix > 50BF Ext Trip
), or
•
A binary or virtual input assigned to
50BF Mech Trip
(
Configuration > Binary Inputs >
Input Matrix > 50BF Mech Trip
).
50BF Ext Trig
Any binary input can be mapped to this input to trigger the circuit-breaker fail function. Current must be
above setting for the function to operate.
50BF Mech Trip
Any binary input can be mapped to this input to trigger the circuit-breaker fail function. For the function to
operate the circuit-breaker closed input is used to detect a failure, not the current.
50BF CB Faulty
Any binary input can be mapped to this input, if it is energized when a trip initiation is received an output will
be given immediately (the timers are by passed).
6.1
6.1.1
6.1.2
Supervision Functions
6.1 50BF Circuit-Breaker Failure Protection – 3 Pole
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Reyrolle 7SR5, Transformer Protection Device, Device Manual
C53000-G7040-C015-1, Edition 11.2019
