PM on Power Breakers and Arc Flash

[brother]

I haven't seen this topic addressed much. I have seen where power breakers have failed to close, and on very rare occassions Ive heard of them failing to OPEN!! The result the gear was horribleMost manufacturers require preventive maintenance/exercising on power breakers, even though alot of places dont do it. Some areas have breakers that have not been exercised in over 20 years!! I do not believe one can do an accurrate ARC FLASH calculation when you have breakers that have not been properly pm. What is your opininon of this issue??

 

[ron]

The calculations are reliant on devices performing as advertised so when PM is required, then it is required.

 

[zog]

I haven't seen this topic addressed much. I have seen where power breakers have failed to close, and on very rare occassions Ive heard of them failing to OPEN!! The result the gear was horrible

We test thousands of breakers every year, and have been collecting data on this for over 25 years.

Over 30% of low and medium voltage power circuit breakers tested that have been in service for more than 24 months in industrial applications will not perform to specification when “as found” trip tests are performed.

After exercise and operation, cleaning and proper lubrication this is reduced to less than 12 %.

Now if you are a large industrial plant that has hundreds of power breakers, how many bad ones do you have based off of those stats?

Most manufacturers require preventive maintenance/exercising on power breakers, even though alot of places dont do it. Some areas have breakers that have not been exercised in over 20 years!! I do not believe one can do an accurrate ARC FLASH calculation when you have breakers that have not been properly pm. What is your opininon of this issue??

Required per NFPA 70E. Article 200 covers the scope and refers to NFPA 70B or NETA MTS for required PM's and frequency of the tests.

Article 205.3 covers OCPD's specifically.

 

[Jim W in Tampa]

How often do they not open at a number that would not likely melt the wires or have loads that were still far under what the wire was rated for ?
Many factories simply can not shut off breakers without disrupting production. Not saying its good idea to ignore but they will take chances

 

[zog]

How often do they not open at a number that would not likely melt the wires or have loads that were still far under what the wire was rated for ?

Well we are talking power breakers here so usually no wires, usually buss or cable and the main concern is the load. The breakers are usually set per a study to ensure motor or other load damage doe not occur. Most of the failures I mentioned would alow the loads to be damaged.

Many factories simply can not shut off breakers without disrupting production. Not saying its good idea to ignore but they will take chances

Nearly all factories have planned outages for doing this type of thing several times a year. And these days not many are running 3 shifts 7 days a week so even less excuses.