On 03/02/2014 12:17, Lawrence wrote:
On Sun, 02 Feb 2014 16:00:41 +0000 (GMT), "Dave Liquorice"
wrote:
On Sun, 02 Feb 2014 15:17:41 +0000, Lawrence wrote:


Last night I had a power cut lasting 2 and half hours. This is
not
unusual in our village but what was unusual was how it started.
Initially the oven switched off and the kitchen ring went off but
all
the lights stayed on albeit dimmer than normal.


What lamps for lighting? CFLs are on or off at more or less the same
brightness over a large supply voltage range. Confused the heck out
of me at 0300 the other winter when an ice storm meant our volts
dropped to not much over 100. CFL lights worked, router, switch,
server where on (SMPSU's), other bits of IT kit not (lump of iron
PSU), tungsten was very red and dim...

Sounds like the sort of thing that happens when there is an abnormal
load on the line which is insufficient to immediately trip out the
protection circuit but enough to drop the volts at consumer unit.

We used to have a problem like that when the sewage pumping station down
the valley switched on at 6.30pm every night the lights would flicker
and dim until the pump got properly up to speed. NEDL replaced that
cable a while ago and it has never been any bother since.


Over the course of the next few minutes, various lighting
circuits went
off and on a few times before eventually all went off.


Synchronous on/off switching or different circuits at different
times. Synchronous would probably be an auto recloser in the feed
some where detecting a fault, tripping then reconnecting a few
seconds later. If this happens more then n times in x minutes it
locks out in the off state. Saves the DNO having to send an engineer
out to reset after transient faults like lightning or a small branch
touching the line.


Mixture of filament, CFL and linear fluorescent. I guess that answers my
query.

CFL and LED will run OK almost as bright on a surprisingly low mains
voltage but draw more current to do so.

--
Regards,
Martin Brown