ABB RELION RET670, Applications Manual

Page: 887 / 1016

N
u
m
b
e
r
o
f
m
a
ke
-b
re
a
k
op
e
ra
tio
n
s
(
n
)
Interrupted current (kA)
P1
P2
100000
50000
20000
10000
2000
5000
1000
100
200
500
10
20
50
0.1 0.2 0.5 1 2 5 10 20 50 100
IEC12000623_1_en.vsd
IEC12000623 V1 EN-US
Figure 406: An example for estimating the remaining life of a circuit breaker
Calculation for estimating the remaining life
The graph shows that there are 10000 possible operations at the rated operating current
and 900 operations at 10 kA and 50 operations at rated fault current. Therefore, if the
interrupted current is 10 kA, one operation is equivalent to 10000/900 = 11 operations
at the rated current. It is assumed that prior to tripping, the remaining life of a breaker
is 10000 operations. Remaining life calculation for three different interrupted current
conditions is explained below.
• Breaker interrupts at and below the rated operating current, that is, 2 kA, the
remaining life of the CB is decreased by 1 operation and therefore, 9999
operations remaining at the rated operating current.
• Breaker interrupts between rated operating current and rated fault current, that is,
10 kA, one operation at 10kA is equivalent to 10000/900 = 11 operations at the
1MRK 504 163-UUS A
Section 18
Monitoring
Transformer protection RET670 2.2 ANSI 881
Application manual