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Section 7
Current protection
CCRBRF can also give a retrip command. This means that a second trip signal is sent to the
protected object circuit breaker. The retrip function can be used to increase the probability of
operation of the breaker, or it can be used to avoid backup trip of many breakers in case of
mistakes during relay maintenance and testing.
7.6.3
Setting guidelines
The parameters for Breaker failure protection CCRBRF are set via the local HMI or PCM600.
The following settings can be done for the breaker failure protection.
GlobalBaseSel : Selects the global base value group used by the function to define IBase , UBase
SBase . Note that this function will only use IBase value.
and
Operation : Off / On to enable/disable the complete function.
FunctionMode : It defines the way the detection of failure of the breaker is performed. In the
Current mode, the current measurement is used for the detection. In the CB Pos mode, the CB
auxiliary contact status is used as an indicator of the failure of the breaker. The mode
CB Pos means that both ways of detections can be activated. The CB Pos mode is used in
or
applications where the fault current through the circuit breaker is small. This can be the case
for some generator protection application (for example, reverse power protection) or in the
case of line ends with weak end infeed.
StartMode : By this setting it is possible to select how t1 and t2 timers are run and
consequently how output commands are given from the function:
•
Option 1 - LatchedStart : "By external start signals which is internally latched".
When function is once started by external
elapse and then measurement criterion defined by parameter
always checked in order to verify if the appropriate command shall be given out from the
function. Timers cannot be stopped by removing the external
be started again only when all of the following three timers
in function internal design has expired and the measurement criterion defined by
parameter
corresponds to the function behavior in previous versions of the 670 Series from version
1.0 up to and including version 2.1.
Option 2 - FollowStart : "Follow the external start signal only".
•
The timers
measurement criterion defined by parameter
verify if the appropriate command shall be given out from the function. Timers can be
always stopped by resetting the external
Option 3- FollowStart&Mode : "Follow external start signal and selected FunctionMode " .
•
The timers
the measurement criterion defined by parameter
then the appropriate command will be given out from the function. Timers can be stopped
by resetting the external
Figure
When one of the two "follow modes" is used, there is a settable timer
block the external
t1 and t2 timers and consequently prevent any backup trip command. At the same time the
STALARM output from the function will have logical value one. To reset this signal external
START signal shall be removed. This is done in order to prevent unwanted operation of the
breaker failure function for cases where a permanent
176
FunctionMode has deactivated, see
t1 and t2 will run while external START signal is present. If they elapse then
t1 and t2 will run while external START signal is present and in the same time
START signal or if the measurement criterion de-activates, see
101.
START input signal when it times-out. This will automatically also reset the
START signal, the timers t1 and t2 will always
FunctionMode will be
START signal. Function can
t1 , t2 and fixed timer of 150ms
Figure
99. Note that this option
FunctionMode will be checked in order to
START signal, see
Figure
FunctionMode is active. If they elapse
START signal is given by mistake (e.g.
1MRK 505 370-UEN D
M11546-4 v10
Current
100.
tStartTimeout which will
Busbar protection REB670
Application manual
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