I MIN may be used as a criterion for starting the meter. The meter can be set or reset. A CFC application
example for such meter is available on the Internet (SIPROTEC Download Area).
Circuit Breaker Maintenance
General
The procedures aiding in CB maintenance allow maintenance intervals of the CB poles to be carried out when
their actual degree of wear makes it necessary. Saving on maintenance and servicing costs is one of the main
benefits this functionality offers.
The universal CB maintenance accumulates the tripping currents of the trips initiated by the protective func-
tions and comprises the four following autonomous subfunctions:
•
Summation tripping current (ΣΙ-procedure)
•
Summation of tripping powers (ΣΙ
x
-procedure)
•
Two-point procedure for calculating the remaining lifetime (2P-procedure)
•
Sum of all Squared Fault Current Integral (I
2
t-procedure);
Measured value acquisition and preparation operates phase-selectively for all four subfunctions. The three
results are each evaluated using a threshold which is specific for each procedure (see Figure 2-123.).
[schema-lsw-171103-kn, 1, en_US]
Figure 2-123
Diagram of CB maintenance procedures
The ΣΙ procedure is always present and active as a basic functionality. However, the other procedures (ΣΙx, 2P
and Ι
2
t) can be selected via a common configuration parameter.
As the load on the switch depends on the current amplitude and duration of the actual switching action,
including arc deletion, determination of the start and end criteria is of great importance. The procedures ΣΙx,
2P and Ι
2
t make use of the same criteria for that purpose. The logic of the start and end criterion is illustrated
in Figure 2-124.
2.23.2.2
Functions
2.23 Auxiliary Functions
280 SIPROTEC 4, 7SJ80, Manual
E50417-G1140-C343-A8, Edition 12.2017
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