Siemens 6MD85, Manual

Page: 1025 / 1256

[LoCBWIxF, 1, en_US]
Figure 9-25 Logic of the Determination of the Tripping Current Value
(1) Current-flow criterion fulfilled
(2) 20 ms prior value
Calculation of the Wear
If the ΣI x -method stage receives the logic release signal, the determined tripping current is used in the calcula-
tion of wear. The calculation results are then added to the existing statistic values of the ΣI x method as
follows, with phase A as example.
[FoCBWIxA-301012-01.tif, 1, en_US]
Where:
x Parameter exponent
q No. of circuit-breaker switching cycle
Tripping/opening current of phase A to the power of x in the qth circuit-
breaker operation
Rated normal current to the power of x
Statistic value of current phase A calculated with the ∑I x method
m Total number of switching cycles
The phase-selective ΣI x value is available as statistical value. You can reset or preset the statistics according to
the specific application.
To simplify the interpretation of the sum of the tripping current powers, the values are set in relation to the
exponentiated rated normal current I
rated
of the circuit-breaker (see also Setting notes).
Circuit-Breaker Maintenance Warning
If the summated ΣI x value of any phase is greater than the threshold, a phase-selective warning signal is
generated.
Measured Values, Energy Values, and Supervision of the Primary System
9.6 Circuit-Breaker Wear Monitoring
SIPROTEC 5, High-Voltage Bay Controller, Manual 1025
C53000-G5040-C015-9, Edition 11.2017