Its a public forum, we can't assume anything!Think I'm a little wiser than to work with out turning the MCCB off but hey.
I would rather risk hurting someone's pride but underestimating them than have to live with overestimating somone by not saying something that ultimately led to an injury.
It would take a very high level of lightning hit to trigger an arc, and this is not a country that sees that every day!There are 66 apartments spread over the 12 floors. Rising main with tap off box ever other floor feeding fuse cabinets for the apartments. Which are in turn fed via split concentric to individual boards. Bear in mind these were fitted around 9 years ago so no surge protection. Interestingly though I was informed today that the apartment block next door it one had power outage yesterday as well might be coincidental but who knows
I'm guessing the flats are all on 60A fuses and if so they have total selectivity with 100A or more, so anything downstream of those fuses cannot be responsible for blowing the incoming 315A fuses.
So from my armchair view it comes down to a fault the rising main or in one of those boxes on the supply side of the flat's fuses.
Or there is some secret unknown big 3-phase load somewhere!