Functions
2.20 Auxiliary Functions
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A5, Release date 11.2012
263
2.20.2 Statistics
The number of trips initiated by the 7SK80 and the operating hours under load are counted. An additional
counter allows the number of hours to be determined in which the circuit breaker is positioned in condition
„open“. Further statistical data can be collected to optimize the intervals for circuit breaker maintenance.
The counter and memory levels are secured against loss of auxiliary voltage.
2.20.2.1 Description
Number of Trips
In order to count the number of trips of 7SK80, the 7SK80 relay has to be informed of the position of the circuit
breaker auxiliary contacts via binary inputs. Hereby, it is necessary that the internal pulse counter is allocated
in the matrix to a binary input that is controlled by the circuit breaker OPEN position. The pulse count value
"Number of TRIPs CB" can be found in the "Statistics" group if the option "Measured and Metered Values Only"
was enabled in the configuration matrix.
Operating Hours
The operating hours under load are also stored (= the current value in at least one phase is greater than the
limit value BkrClosed I MIN set under address 212).
Hours Meter "CB open"
A meter can be realized as a CFC application if it adds up the number of hours in state „Circuit Breaker open“
similarly to the operating hours meter. The universal hours meter is linked to a respective binary input and
counts if the binary input is active. Alternatively, the undershooting of the parameter value 212 BkrClosed 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).
2.20.2.2 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 functions
and comprises the four following autonomous subfunctions:
• Summation tripping current (ΣI-procedure)
• Summation of tripping powers (ΣI
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 2-100).
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