Functions
2.16 Breaker Failure Protection 50BF
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008
282
2.16.2
Setting Notes
General
Breaker failure protection is only effective and accessible if address
170
50BF
is set to
Enabled
or
enabled
w/ 3I0>
. Setting
Enabled
considers the three phase currents for total current monitoring. Setting
enabled
w/ 3I0>
additionally evaluates the ground current or the negative sequence system when only one phase
current occurs.
If this function is not required, then
Disabled
is set. The function can be set to
ON
or
OFF
under address
7001
FCT 50BF
.
Criteria
Address
7004
Chk BRK CONTACT
establishes whether or not the breaker auxiliary contacts connected via
binary inputs are to be used as a criterion for pickup. If this address is set to
ON
, then current criterion and/or
the auxiliary contact criterion apply. This setting must be selected if the circuit breaker failure protection is
started by functions, which do not always have a certain criterion for detection of an open circuit breaker, e.g.
voltage protection.
Time Delay
The time delay is entered at address
7005
TRIP-Timer
. This setting should be based on the maximum circuit
breaker operating time plus the dropout time of the current flow monitoring element plus a safety margin which
takes into consideration the tolerance of the time delay. Figure 2-105 illustrates the time sequences.
Figure 2-105
Time sequence example for normal clearance of a fault, and with circuit breaker failure
Pickup Values
The pickup value of the current flow monitoring is set under address
7006
50BF PICKUP
, and the pickup value
of the ground current monitoring under address
7007
50BF PICKUP IE>
. The threshold values must be set
at a level below the minimum fault current for which the total current monitoring must operate. A setting of 10%
below the minimum fault current for which breaker failure protection must operate is recommended. The pickup
value should not be set too low since otherwise there is a risk that transients in the current transformer second-
ary circuit may lead to extended dropout times if extremely high currents are switched off.
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