Siemens siprotec SJ62 User Manual page 327

2 Functions
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since the remaining lifetime is decremented with each trip by the corresponding
number of operating cycles. If one of the three phase values drops below the thresh-
old, a corresponding message will be triggered.
A double-logarithmic diagram provided by the CB manufacturer illustrates the relation-
ship of operating cycles and tripping current (see example in Figure 2-118). This
diagram allows the number of yet possible trips to be determined (for tripping with
equal tripping current). According to the example, approximately 1000 trips can yet be
carried out at a tripping current of 10 kA. The characteristic is determined by two ver-
tices and their connecting line. Point P1 is determined by the number of permitted op-
erating cycles at rated operating current Ir, point P2 by the maximum number of oper-
ating cycles at rated fault tripping current Isc. The associated four values can be
configured.
Figure 2-118 Diagram of operating cycles for the 2P procedure
Since figure 2-118 shows a double-logarithmic representation, the line connecting P1
and P2 can be described by means of the following exponential equation:
m
n = b·I
b
where n is the number of operating cycles, b the operating cycles at I
ping current, and m the directional coefficient.
The general line equation for the double-logarithmic representation can be derived
from the exponential function and leads to the coefficients b and m.
= 1A, I
b
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015
the trip-
b