ABB SF6 LTB 245E1 BLG 1002A Product Manual page 75

Preventative maintenance
2.1.2 Service life of arcing contacts with short-circuit interruption
2.1.3 Tightness checking
4
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.
Number of interruptions
n
5000
2000
1000
500
200
100
50
20
2
Figure 2-1. Number of operations with short-circuit current.
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.
Operating and Maintenance Instructions
LTB 245E1
3 4 5 10
LTB 420E2
20 30 40 50 63
Short-circuit current
1HSB435409-100 en1
kA