Table 32: Dependencies between parameters RetripMode and FunctionMode
RetripMode FunctionMode
Description
Off
N/A The re-trip function is disabled
UseFunctionMode Current
A phase current should be larger
than the set operate level to allow
re-trip once the
t1
timer elapses
CB Pos
Re-trip is done when the breaker
position indicates that breaker is
still closed after re-trip time has
elapsed
Current or CB Pos
Both the methods are used
Always
N/A Re-trip is always given when
t1
elapses without any further
checks
BuTripMode
: Defines how many current criterias to be fulfilled in order to detect failure of the
breaker. For
Current
operation
2 out of 4
means that at least two currents, of the three-phase
currents and the residual current, shall be high to indicate breaker failure.
1 out of 3
means
that at least one current of the three-phase currents shall be high to indicate breaker failure.
1
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
1 out of 3
is sufficient. For
CB Pos
operation
1 out of 3
is always used.
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
IBase
. Note that this setting shall not be set lower than 4% of Ir,
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
IBase
. It
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
BuTripMode
shall
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
IBase
.
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).
Timer
t2
is used when function is started in one phase only (i.e. for single-phase to ground
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:
margin
BFP_reset
CB_open
t2 t1 t t t
IECEQUATION18191 V1 EN-US
(Equation 41)
Section 7 1MRK 505 370-UEN D
Current protection
178 Busbar protection REB670
Application manual
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