2.15 It Function (current-time integral)
163
7ST6 Manual
E50417-G1176-C251-A3
the 2P-procedure. All trips counted in this manner can be retrieved under the statistical
value
„mechan.TRIP=“
(FNo. 16011).
2.15.3 Setting Notes
General
The determination of the circuit breaker load in accordance with the It or 2P-procedure
can only operate if you have set address
141
FCT It-Calc.
to
Start by Aux
or
Start by TRIP
during configuration of the functional scope. Additionally, the
It
FUNCTION
in address
4101
and via the binary inputs
„>It ON“
(FNo. 13845) and
„>It OFF“
(FNo. 13846)
ON
— and
OFF
can be set. When the function is switched
on, the indication
„It ACTIVE“
(FNo. 13850) or
„2P ACTIVE“
(FNo. 13857) is gen-
erated.
IT Procedure
The following paragraphs apply to the IT procedure, however, not to the 2P-procedure.
This is set out in detail in the following.
When setting the parameter (address
141
) that configures the functions, you select at
the same time the method for determining the starting time
t
start
of the It procedure. If
the circuit breaker auxiliary contacts are connected to the device, select method
Start by Aux
.
Time Difference CB
Main and Auxiliary
Contact
This setting is only needed if you have selected the method
Start by Aux
when
configuring the It procedure.
The moment of opening of the circuit breaker main contact can only be determined in-
directly by acquisition of the circuit breaker auxiliary contacts. In the 7ST6 device the
indication
„>Brk Aux NC“
(FNo. 4602) is used for this purpose. The circuit breaker
main contact may open before or after the circuit breaker auxiliary contact. The time
difference between the switching of these two contacts is set with the parameter
DELTA AuxCont
(address
4103
). A positive value is set for this time difference if the
auxiliary contact opens or closes later than the main contact.
CB Response Time
This setting is only needed if you have selected the method
Start by TRIP
when
configuring the It procedure.
The moment of opening of the circuit breaker main contact can only be determined in-
directly by means of a preset time difference between the TRIP command and the
opening of the circuit breaker main contacts. This time difference is set in address
4102
T00
.
Circuit Breaker
Alarm
The current value
I dt
, which is accumulated over all trips, is a measure for the circuit
breaker load and can be used for planning the circuit breaker maintenance.
The limit for this measure of the circuit breaker load is set in address
4104
It ALARM
.
When the threshold is reached, the alarm
„It Alarm“
(FNo. 13847) is output.
2P-procedure
This procedure, together with the It procedure, uses the same configuration parameter
It FUNCTION
(address
141
) under "Functional Scope" and the same activation pa-
rameter
It FUNCTION
(address
4101
) under "It Function".
All parameters relevant to this procedure are available in the parameter block
P.System Data 1
(see chapter 2.1.3).
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