2.1 General
35
7ST6 Manual
E50417-G1176-C251-A3
Circuit Breaker
At address
239
T-CB close
the operating time of the connected circuit breaker is
set for the CLOSE command. This operating time will be taken into account by the
Sync. Check
function when closing the circuit breaker.
At address
237
the operating time of the circuit breaker
T CB BREAKTIME
is set for
the TRIP command. This time is taken into account for tripping to determine the dura-
tion of the current-time integral.
In address
240
the minimum trip command duration
TMin TRIP CMD
is set. This
setting applies to all protective functions that initiate tripping. It also determines the
length of the trip pulse when a circuit breaker trip test is initiated via the device. Each
trip command is extended by at least the time set here. This time must be chosen to
ensure a reliable tripping of the breaker. This parameter can only be altered with
DIGSI
®
under
Additional Settings
.
In address
241
the maximum close command duration
TMax CLOSE CMD
is set. This
applies to all close commands issued by the device. It also determines the length of
the close command pulse when a circuit breaker test cycle is issued via the device. It
must be chosen to ensure that the circuit breaker can always close reliably. There is
no risk in setting this time too long, as the close command will in any event be termi-
nated following a new trip command from a protection function. This parameter can
only be altered with DIGSI
®
under
Additional Settings
.
The 7ST6 allows a circuit breaker test during operation by means of a tripping and a
closing command entered on the front panel or via DIGSI
®
. The duration of the trip
command is set as explained above. Address
242
T-CBtest-dead
determines the
duration from the end of the trip command until the start of the close command for this
test. It should not be less than 0.1 s.
At address
243
TEST CB CIRCUIT
you can choose the trip circuits in which a circuit
breaker test is to be performed. For an initial test, you should test both breaker circuits
individually and one after the other in order to achieve a maximum of security.
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