City Power breaker tripping

[Andrew_van_Zyl]

Take the back end of your screwdriver and tap that breaker lightly on it's side. If it then trips, it's shot.

This is a trick that my tutor taught me in the 70's and it has been usefull on many occasions throughout the years.

Thanks Brother. Good suggestion. The breaker stood up to some quite enthusiastic tapping but stayed on. CP replaced the cb recently. Out of ideas here

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[GCE]

Been thinking on this one - Do you have an isolator or CB as mains in the DB

If city power is 80Amp - I would put a 60 amp in the DB on mains to see if that trips first

My gut tells me you have a cable fault that is tripping when it blows clear which is why your megga test does not pick up an issue - An hour or so later once water has got back into the problem area it will sit and short until it blosws again
Test after and hour or 2 of being on.

Had similar on 2 x 120sqmm in parallel - Cable must have been damaged years ago and took almost 15 years before the fault become a complete nuisance - It was under a concrete yard and we were just lucky that while we were standing there we saw wisp of smoke come out between concrete joints - dug down and found the cable fault.

[Andrew_van_Zyl]

Good suggestion GCE - Thank you. Weirdly the problem has gone away and the client is less noisy. I will re-visit this if and when.

Lol at wisps of smoke - generally a sign of trouble!