5.2.2
Function block
Figure 421: Function block
5.2.3
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.
5.2.4
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.
Protection related functions
1MRS757644 H
806
620 series
Technical Manual
