Nuisance tripping of Air Circuit breaker

[jimdevonshire]

MY main incomer to my building is protected by a 450kva/625A ACB it trips now and again but: there is no averload my max demand is 333kva, there is no fault on any of my circuits and the electricity board is saying that they have not had any problems with the supply voltage on any phase. Is it likely to be a dodgy breaker or could there be another cause. Gratefull for any help

 

[peebee]

What's it tripping on? Overcurrent? Some other relay? How old is this -- are the relays electronic or induction disk? When's the last time the relays were calibrated? When's the last time the breaker was overhauled?

You need to provide more specifics. Your question sounds something like: "My car keeps breaking down. Any idea why?"

 

[Crowbar1]

I once had an Allis-Chalmers 5KV breaker trip for no reason several random times. It's culprit turned out to be a latching mechanism very much in need of cleaning and lubricating.

 

[nukeman]

You might what to check for harmonics. Read phase currents and neautral current.

 

[peebee]

Don't forget the possibility that it's operating correctly and protecting you against intermittent ground faults or some other problem.

 

[ruggedscot]

This is one that you have to watch, firstly the breaker age has to be checked and how often it has been serviced, you also have to consider especially in todays climate just how much loading can be attributed to computer based loads or anything being fed of an inverter drive aircon and building ventilation uses such things nowadays and this can add to the harmonic content and also produce over currents in the neutral line.