ABB SF6 LTB 245E1 BLG 1002A, Product Manual

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Preventative maintenance Operating and Maintenance Instructions
4
1HSB435409-100 en1
2.1.2 Service life of arcing contacts with short-circuit interruption
The diagram below shows the number of interruptions versus short-circuit current
that the contacts in a LTB E circuit-breaker can manage before the metal losses due
to burning becomes so great that they must be replaced.
Figure 2-1. Number of operations with short-circuit current.
2.1.3 Tightness checking
The circuit-breakers are equipped with density monitors for checking the gas
density. Each density monitor is equipped with an alarm contact that gives an
electric signal in the event of abnormal leakage. Alarm level 1 gives an alarm signal
while alarm level 2 blocks.
N.B. A new or overhauled circuit-breaker should be checked for tightness by
reading the density monitors after about 1 month and then at 1-2 year
intervals in connection with the regular ocular inspections.
5000
2000
1000
20
500
50
100
200
20 10 2 4 5 3 30 40 50 63
n
kA
Number of interruptions
Short-circuit current
LTB 245E1
LTB 420E2