3.4 Circuit breaker condition
monitoring
VAMP 24h support phone +358 (0)20 753 3264
5038.1
1250
31000
ln
80
10000
ln
n
65038.1
10454125010000 a
Using Equation 3.4-1the relay gets the number of permitted
operations for current 6 kA.
Thus the maximum number of current breaking at 6 kA is 945.
This can be verified with the original breaker curve in Figure
3.4-1. Indeed, the figure shows that at 6 kA the operation count
is between 900 and 1000. A useful alarm level for operation-
left, could be in this case for example 50 being about five per
cent of the maximum.
Example of operation counter decrementing when the CB is
breaking a current
Alarm2 is set to 6 kA. CBFP is supervising trip relay T1 and
trip signal of an overcurrent stage detecting a two phase fault
is connected to this trip relay T1. The interrupted phase
currents are 12.5 kA, 12.5 kA and 1.5 kA. How much are
Alarm2 counters decremented ?
Using Equation 3.4-1 and values n and a from the previous
example, the relay gets the number of permitted operation at
10 kA.
313
12500
10454
5038.1
6
10
kA
C
At alarm level 2, 6 kA, the corresponding number of operations
is calculated according
Equation 3.4-4
Thus Alarm2 counters for phases L1 and L2 are decremented
by 3. In phase L1 the currents is less than the alarm limit
current 6 kA. For such currents the decrement is one.
To Next Page
Loading...
