ABB RET670 Applications Manual page 478

Section 3
IED application
472
applications 1 out of 3 is sufficient. For Contact operation means 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 IBase.
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
FunctionMode is set 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 IBase.
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 BuTripMode is set
1 out of 4. The current setting should be chosen in accordance to the setting of the
sensitive ground-fault protection. The setting can be given within the range 2 – 200 %
of IBase.
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 t t
cbopen BFP reset _
EQUATION1430 V1 EN
where:
t is the maximum opening time for the circuit breaker
cbopen
t is the maximum time for breaker failure protection to detect correct breaker function (the
BFP_reset
current criteria reset)
t is a safety margin
margin
+
t
margin
1MRK504116-UUS C
(Equation 369)
Application manual