Siemens SIPROTEC 4 7SJ61 Manual page 200

Functions
2.17 Auxiliary Functions
[lsw-2p-schaltspiel270404-he, 1, en_US]
Figure 2-77
As Figure 2-77 illustrates a double-log diagram, the straight line between P1 and P2 can be expressed by the
following exponential function:
n = b·Ι m
b
where n is the number of operating cycles, b the operating cycles at Ι
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.
NOTE
i
i
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 Ιsc (263 OP.CYCLES
Isc) is used instead as the calculation result for the current number of operating cycles, see
200
Diagram of operating cycles for the 2P procedure
= 1A, Ι the tripping current, and m the
b b
Figure
SIPROTEC 4, 7SJ61, Manual
C53000-G1140-C210-6, Edition 05.2016
2-78.