Siemens SIPROTEC 4, User Manual

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[lsw-2p-schaltspiel270404-he, 1, en_US]
Figure 2-140 Diagram of operating cycles for the 2P procedure
As Figure 2-140 illustrates a double-log diagram, the straight line between P1 and P2 can be expressed by the
following exponential function:
n = b·
Ι
b
m
where n is the number of operating cycles, b the operating cycles at
Ι
b
= 1A,
Ι
b
the tripping current, and m the
directional coefficient.
The general line equation for the double-logarithmic representation can be derived from the exponential func-
tion and leads to the coefficients b and m.
i i
NOTE
Since a directional coefficient of m < -4 is technically irrelevant, but could theoretically be the result of
incorrect settings, it is limited to -4. If a coefficient is smaller than -4, the exponential function in the oper-
ating cycles diagram is deactivated. The maximum number of operating cycles with
Ι
sc (263
OP.CYCLES
Isc
) is used instead as the calculation result for the current number of operating cycles, see Figure 2-141 .
Functions
2.25 Auxiliary Functions
324 SIPROTEC 4, 7SJ62/64, Manual
C53000-G1140-C207-8, Edition 08.2016