Praise the UPS

[#1]

I think I posted about this strange issue a while back but I just had one of those strange power failures. The power failed for about a second three times within a few minutes. My Sky+ box nearly had a fit, I thought it was destroyed. Of course the computers etc were fine thanks to the 3Kva UPS, exactly the reason I bought it.
We get those strange power failures from time to time and I have no idea why. I would understand if there was nearby lightning but there is not. Can anyone offer any possible explaination?

[#2]

could be any thing, one near me was a swan flew into the feed to the main substation
Another a new  housing estate near me was planned for 2000 houses, now at 3000 plus, surprise, the feed to the estate was no good

[#3]

We get something similar around here from time to time.
What I think it is is that there is - in theory - double redundancy in the power distribution system.
What seems to happen is that the main circuit trips out (for whatever reason), which then fails over to the first backup circuit.
What should happen then is that the first backup circuit should take the strain. However, for reasons which are probably due to lack of maintenance (it costs money, y'know - think of all the profit not being made for shareholders), the first backup circuit can't hold it, and that trips out as well.
This throws all the weight onto the second backup circuit. Rinse and repeat, as it were, because that will be in the same condition as the first one (if not worse), and so that trips out, plunging the area into darkness anyway.
So you get a sequence of off-on-off-on (each lasting a few seconds) and then off (for anything up to two hours).

[#4]

We occasionally get outages, usually due to high winds or blizzards. Sometimes they seem to have no cause,  But, when the mains goes off several times for a second or two, it is due to the autorecloser in action trying to restore the power without human intervention!  There is a little bit about it here.
So my 2KVA UPS overrides them and shuts down the computer gracefully if the supply disappears for much longer!