Siemens 6MD85, Manual

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NOTE
Since a slope coefficient of m < -4 is technically irrelevant, but could theoretically be the result of incorrect
settings, the slope coefficient is limited to -4. If a coefficient is smaller than -4, the exponential function in
the switching-cycles diagram is deactivated. The maximum number of switching cycles with I
sc
is used
instead as the calculation result for the current number of switching cycles, as the dashed line with m =
-4.48 shows in following figure.
[DwCBWSlo, 1, en_US]
Figure 9-28 Value Limitation of Slope Coefficient
(1) Applied function from m < -4
(2) Parameterized function with m = -4.48
(3) Parameterized function with m = -1.77
If the 2P-method stage receives the logic release signal, the current number of used up switching cycles (in
relation to the number of switching cycles at rated normal current) is calculated based on the determined trip-
ping current. This value is subtracted from the the remaining lifetime (switching cycles). The remaining life-
time is available as statistic value. For better understanding, refer to the example below.
You can reset or preset the statistical values according to the specific application. The reset operation changes
the statistic values to 0, and not to their default values of 10 000.
The statistic value of the residual switching cycles is calculated according to the following formula:
[FoCBW2P2-301012-01.tif, 1, en_US]
Measured Values, Energy Values, and Supervision of the Primary System
9.6 Circuit-Breaker Wear Monitoring
SIPROTEC 5, High-Voltage Bay Controller, Manual 1029
C53000-G5040-C015-9, Edition 11.2017