Siemens SIPROTEC 7ST6, Руководство пользователя, Страница: 159 / 356

2.15 It Function (current-time integral)
159
7ST6 Manual
E50417-G1176-C251-A3
2.15.2 Function Description 2P-procedure
General In the 2P-procedure the CB manufacturer's double-log operating cycle diagrams and
the fault current measured at the time of contact separation serve as a basis for the
calculation of the remaining lifespan. The data supplied by the CB manufacturer is
transformed in such manner that, by means of measuring the fault currents, a concrete
statement can be made with regard to the still possible operating cycles.
The calculated remaining lifespan represents the number of still possible trips of cur-
rents as high as the rating operating current. It is displayed as a statistical value. The
display does not indicate a unit and no decimals. As for the other procedures, the re-
maining lifespan is verified against a limit value. This forms the "lower limit" here, as
the remaining lifespan decrements with each trip by a number of operating cycles in
correspondence with the fault current. If the limit value is exceeded, a respective indi-
cation is generated.
Initiation The 2P-procedure can be initiated by different sources.
In case of an internal protective tripping, the start criterion is complied with by means
of generation of the group indication "Device OFF" (D-OFF).
An externally initiated trip command can be taken into consideration if it is sent simul-
taneously via a binary input on the message
„>2P start“
(FNo. 16019). As a further
initiation criterion the edge of the coming indication
„>Brk Aux NC“
(FNo. 4602) can
be used as it is herewith signalled that the mechanism of the circuit breaker has been
set in motion to separate the contact.
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