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4-14
Supporting Functions
857-UM001A-EN-P – July 2009
Clearing "Operations Left" Counters
After the breaker curve table is filled and the alarm currents are
defined, the wearing function can be initialized by clearing the
decreasing operation counters with parameter "Clear" (Clear
oper. left cntrs). After clearing the device will show the
maximum allowed operations for the defined alarm current
levels.
Operation Counters to Monitor the Wearing
The operations left can be read from the counters "Al1Ln"
(Alarm 1) and "Al2Ln" (Alarm2). There are three values for
both alarms, one for each phase. The smallest of three is
supervised by the two alarm functions.
Logarithmic Interpolation
The permitted number of operations for currents in between the
defined points are logarithmically interpolated using the
following equations:
Equation 4.1
a
C =
, where
n
I
C = permitted operations
I = interrupted current
a = constant according Equation
n = constant according Equation
Equation 4.2
C
k
ln
C
=
+
k
1
n
I
+
k
1
ln
I
k
Equation 4.3
a =
2
C
I
k
k
ln
=
natural logarithm function
C
=
permitted operations.
k
I
=
corresponding current.
k
C
=
permitted operations.
k+1
I
=
corresponding current.
k+1
k = row 2...7 in Table 4.13.
k = row 2...7 in Table 4.13.
k = row 2...7 in Table 4.13.
k = row 2...7 in Table 4.13.
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