In article ,
Graham. writes:
I am trying to help some friends discover what is wrong with their
electrics.

The last 3 or 4 times I have visited them I have heard a thud, and the
lights blink at the same moment. This happens maybe twice per hour,
but not regularly enough to be able to predict the next event.

Does it happen all the time, e.g. including all through the night,
or only during the day? What about weekends?

My friends had not attached any significance to these events until I
called them catastrophic explosions, now they are worried. They hadn't
noticed the lights flicker at all, they had heard the thuds but put it
down to their neighbours door slamming, which isn't unreasonable
having heard it.

All the circuits are affected, lights and power.

Well, it could still be something next door, interfering with the
local mains supply.

Could the bang be a breaker tripping off next door?

Is the flicker a momentary brown-out, or a momentary surge
(which can happen if there's a short circuit on another phase
which momentarily yanks the neutral part way to that phase
voltage)?

Brown-outs and surges can show up better with mains filament
lamps, because they amplify the effect.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]