ABB RELION 620 Series Technical Manual page 814

Section 5
Protection related functions
5.2.3
5.2.4
808
Functionality
The circuit breaker failure protection function CCBRBRF is activated by trip
commands from the protection functions. The commands are either internal
commands to the terminal or external commands through binary inputs. The start
command is always a default for three-phase operation. CCBRBRF includes a three-
phase conditional or unconditional retrip function, and also a three-phase conditional
back-up trip function.
CCBRBRF uses the same levels of current detection for both retrip 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 retrip 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.
Operation principle
The function can be enabled and disabled with the Operation setting. The
corresponding parameter values are "On" and "Off".
The operation of CCBRBRF can be described using a module diagram. All the
modules in the diagram are explained in the next sections. Also further information on
the retrip and backup trip logics is given in sub-module diagrams.
I_A
Level
I_B detector
1
I_C
POSCLOSE
START
Level
Io detector
2
Timer 3
t
CB_FAULT
BLOCK
A070445 V3 EN
Figure 412: Functional module diagram
Level detector 1
The measured phase currents are compared phasewise to the set Current value. If the
measured value exceeds the set Current value, the level detector reports the exceeding
Timer 1
Start
t
logic
Timer 2
t
1MRS757644 F
Retrip
TRRET
logic
Back-up
trip TRBU
logic
CB_FAULT_AL
620 series
Technical Manual