ABB REL670 2.2 IEC, Applications Manual

Page: 515 / 908

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. Typical setting is 10% of
IBase .
I>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 .
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-earth faults in these systems it is necessary to measure the
residual current separately. Also in effectively earthed systems the setting of the
earth-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 earth-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:
_
2 1
³ + + +
cbopen BFP reset margin
t t t t t
EQUATION1430 V1 EN-US
(Equation 483)
where:
t
cbopen
is the maximum opening time for the circuit breaker
t
BFP_reset
is the maximum time for breaker failure protection to detect correct breaker function (the
current criteria reset)
t
margin
is a safety 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.
1MRK 506 369-UEN B
Section 9
Current protection
Line distance protection REL670 2.2 IEC 509
Application manual