Coming to this rather late - having lacked the spare time till now to wade through 5+ pages ...
I've had faults at work where a computer PSU with (I assume) a local fuse of no more than probably 3.15A rating has taken out a 32A breaker when it went - killing everything else on the same power strip in the rack.
Before the answer was given, I'd have said something along the lines of "pretty well any random combination - possibly including all the fuses and breakers".
On the why didn't the 10A fuse blow while the 32A MCB tripped, but the 5A fuse did blow ...
When the breaker trips, there will indeed be a period between when the current reaches a level that "fires" the mechanism and the contacts actually opening. It'll be very short, but definitely non-zero. During this time, the fault current is still flowing - so the 5A fuse can blow, remove the fault current, but the breaker will still trip.
Add to that the fact that a fuse does not instantaneously stop the fault current when it does break. When the wire breaks, an arc forms across the short gap and the current continues to flow until the arc has grown (by the wire melting away) to a length where the supply voltage is no longer enough to maintain it. Thus the fuse can have blown but still be passing enough fault current to still trip the breaker. I'm told that the effect of using a fuse on a higher voltage than it is design for can be "quite spectacular" as the higher voltage supports an arc longer than the fuse !
Add these two together, and no I'm not surprised at all.
I would also not be surprised if the 10A fuse blew at some random point in the future for no apparent reason. It's fuse wire will have been very hot, perhaps even to melting point, and then cooled. The size/shape of the wire is likely to have changed, and it's surface will have oxidised. So the actual effective size of the fuse wire is now different to when it was made - most likely smaller at some points.
I have, myself, managed to blow several fuses in one go when introducing an ... err 'fault' through carelessness (I know better now, honest guv
). More usual when they are the same rating (eg all 13A), but I've done it with different rating fuses.
For the 16A breaker to not trip, well I guess it's just a smidgen slower than the 32A one. There will always be some variation - especially if they are different makes, or even just different batches of the same make/design.
