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Section 7
Current protection
Table 32:
RetripMode
Off
UseFunctionMode
Always
BuTripMode : Defines how many current criterias to be fulfilled in order to detect failure of the
breaker. For
currents and the residual current, shall be high to indicate breaker failure.
that at least one current of the three-phase currents shall be high to indicate breaker failure.
out of 4 means that at least one current of the three phase currents or the residual current
shall be high to indicate breaker failure. In most applications
operation
IP> : Current level for detection of breaker failure, set in % of IBase . This parameter should be
set so that faults with small fault current can be detected. The setting can be chosen in
accordance with the most sensitive protection function to start the breaker failure protection.
Default setting is 10% of
where Ir is rated current of the IED CT input where the function is connected. In principle Ir is
either 1A or 5A depending on the ordered IED.
I>BlkCBPos : If the FunctionMode is set to Current or CB pos breaker failure for high current
faults are safely detected by the current measurement function. To increase security for low
currents the contact based function will be enabled only if the current at the moment of
starting is below this set level. The setting can be given within the range 5 – 200% of
is strongly recommended to set this level above IPh> set level.
IN> : Residual current level for detection of breaker failure set in % of IBase. In high impedance
earthed systems the residual current at phase- to-earth faults are normally much smaller than
the short circuit currents. In order to detect breaker failure at single phase-to-earth faults in
such systems it is necessary to measure the residual current separately. The
be set
1 out of 4 in such systems The current setting should be chosen in accordance to the
setting of the sensitive earth-fault protection. The setting can be given within the range 2 –
200 % of
t1 : Time delay of the retrip. The setting can be given within the range 0 – 60s in steps of 0.001
s. Typical setting is within range 0 – 50ms.
t2 : Time delay of the backup trip. The choice of this setting is made as short as possible at the
same time as unwanted operation must be avoided. Typical setting is within range 90 – 200ms
(also dependent of retrip timer).
t2 is used when function is started in one phase only (i.e. for single-phase to ground
Timer
fault on an OHL (Over Head Lines) when single-pole auto-reclosing is used).
The minimum time delay for the backup trip can be estimated as:
t2 t1 t
IECEQUATION18191 V1 EN-US
178
Dependencies between parameters RetripMode and FunctionMode
Current operation 2 out of 4 means that at least two currents, of the three-phase
1 out of 3 is always used.
IBase . Note that this setting shall not be set lower than 4% of Ir,
IBase .
t
t
margin
CB_open
BFP_reset
FunctionMode
N/A
Current
CB Pos
Current or CB Pos
N/A
1MRK 505 370-UEN D
Description
The re-trip function is disabled
A phase current should be larger
than the set operate level to allow
re-trip once the
t1 timer elapses
Re-trip is done when the breaker
position indicates that breaker is
still closed after re-trip time has
elapsed
Both the methods are used
Re-trip is always given when
elapses without any further
checks
1 out of 3 means
1 out of 3 is sufficient. For CB Pos
BuTripMode shall
(Equation 41)
Busbar protection REB670
Application manual
t1
1
IBase . It
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