ABB Relion 650 Series Applications Manual page 96

Section 7
Current protection
indicate breaker failure. In most applications
back-up trip is done when circuit breaker is closed (breaker position is used).
Pickup_PH : 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.
Typical setting is 10% of
Pickup_BlkCont : If any contact based detection of breaker failure is used this function can be
blocked if any phase current is larger than this setting level. If the
Current&Contact breaker failure for high current faults are safely detected by the current
measurement function. To increase security the contact based function should be disabled for
high currents. The setting can be given within the range 5 – 200% of
Pickup_N : Residual current level for detection of breaker failure set in % of IBase . In high
impedance grounded systems the residual current at phase- to-ground faults are normally much
smaller than the short circuit currents. In order to detect breaker failure at single-phase-ground
faults in these systems it is necessary to measure the residual current separately. Also in
effectively grounded systems the setting of the ground-fault current protection can be chosen to
relatively low current level. The
in accordance to the setting of the sensitive ground-fault protection. The setting can be given
within the range 2 – 200 % of
t1 : Time delay of the re-trip. The setting can be given within the range 0 – 60s in steps of 0.001 s.
Typical setting is 0 – 50ms.
t2 : Time delay of the back-up 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 90 – 200ms (also dependent
of re-trip timer).
The minimum time delay for the re-trip can be estimated as:
³ +
t 2 t 1
EQUATION1430 V1 EN-US
where:
t
cbopen
t
BFP_reset
t
margin
It is often required that the total fault clearance time shall be less than a given critical time. This
time is often dependent of the ability to maintain transient stability in case of a fault close to a
power plant.
90
IBase . Set the parameter IP> lower than the parameter I>BlkCont .
BuTripMode is set 1 out of 4 . The current setting should be chosen
IBase .
+ +
t t t
cbopen BFP reset _ margin
is the maximum opening time for the circuit breaker
is the maximum time for breaker failure protection to detect correct breaker function
(the current criteria reset)
is a safety margin
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1 out of 3 is sufficient. For Contact operation means
FunctionMode is set
IBase .
1MRK 505 287-UUS B
(Equation 17)
Busbar protection REB650
Application manual