Technical description
3 Supporting functions
3.5 Circuit breaker condition
monitoring
VM59.EN001
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115
Table 3.5-1. An example of circuit breaker wearing
characteristics in a table format. The values are taken from
the figure above. The table is edited with VAMPSET under
menu "BREAKER CURVE".
Point
Interrupted current
(kA)
Number of permitted
operations
1
0 (mechanical age)
10000
2
1.25 (rated current)
10000
3
31.0 (maximum breaking current)
80
4
100
1
5
100
1
6
100
1
7
100
1
8
100
1
Setting alarm points
There are two alarm points available having two setting
parameters each.
Current.
The first alarm can be set for example to nominal current of
the CB or any application typical current. The second alarm
can be set for example according a typical fault current.
Operations left alarm limit
An alarm is activated when there are less operation left at
the given current level than this limit.
Any actual interrupted current will be logarithmically weighted
for the two given alarm current levels and the number of
operations left at the alarm points is decreased accordingly.
When the "operations left" i.e. the number of remaining
operations, goes under the given alarm limit, an alarm signal is
issued to the output matrix. Also an event is generated
depending on the event enabling.
Clearing "operations left" counters
After the breaker curve table is filled and the alarm currents
are defined, the wearing function can be initialised by clearing
the decreasing operation counters with parameter "Clear"
(Clear oper. left cntrs). After clearing the relay 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.
