In message
,
therustyone writes
On Mar 8, 10:27Â*am, Ian Jackson
wrote:
In message , puffernutter
writes

On 08/03/2011 09:09, MM wrote:
I believe someone was recently talking about voltage spikes, though I
can't find the thread in Google Groups to hang this on. I happened to
be watching my consumption thingy this morning and noticed that it was
constant at 249 volts. Then it went up to 250 for 30 seconds, back
down to 249, then back up to 250 again. For a good five minutes it
hovered around 249-250. Then it came down to 248, then 247.

Aren't these spikes damaging to sensitive equipment? (TVs, DVD Players
etc) I don't worry about the PC because I have a UPS on it. The
voltage is ~supposed~ to be 240 in the UK.

MM

Voltage in the UK was harmonised with Europe on 1st January 1995 and is
supposed to be 230V +10%-6% (216.2€“253 V).

So, your fluctuations are within tolerance. Â*Most equipment is designed
to work at 110v - 220v (at 50 or 60Hz) look at the rating plate. Â*That
voltage is nominal and will not include the tolerance.

Some time before Christmas, I inherited from a deceased works colleague
a purpose-built home-made meter for measuring the mains voltage (a 4"
moving-coil meter + rectifier). After testing it and tweaking it
slightly so that it read correctly at 230V, I left it plugged in,
sitting on the desk, so that I could instantly see how the mains was
doing. I have seen some considerable variations.

Before Christmas, the typical 'normal' voltage was 230V, occasionally
going up to 235. However, when the really cold weather started, after
around 5pm, the voltage would start to drop and, on several days,
regularly fell to 215V. The lowest (checked on a couple of digital
meters) was 214.4V.

After the New Year, have noticed that the typical 'normal' seems to be
235V (even when it was still very cold), and I occasionally see as high
as 245V. [Presumably someone decided to change the output tap at the
substation.] However, a couple of nights ago, I noticed that, every 30
seconds or so, the lights were very obviously suddenly going alternately
dim and bright. The mains was abruptly jumping between 230 and 220V, and
I was rather concerned that this might indicate that a power cut was
about to happen. However, an hour later, things settled down, and the
mains was a steady 235V again.
--
Ian

but did the frequency go down with the volts? I have a far eastern
LED Lloytron clock that seems to sync to the mains. If the frequency
goes down the clock runs slow.

No. I haven't been monitoring the mains frequency. I've only been
keeping an eye on the volts (simply because I acquired the meter, which
sits permanently plugged in, on a corner of the desk).

I was surprised to see how low the voltage sometimes went (right down to
the minimum limit). When it was really cold over Christmas and New Year,
I expect the guys at the power stations were shovelling coal for all
they were worth, and that the frequency (which is of less interest than
the voltage) was well down on normal.

Obviously, any type of clock which uses the mains frequency will run
fast or slow if the frequency varies. My understanding is that the
generating people are supposed make sure that, come hell or high water,
during a 24 hour period the correct number of cycles are delivered, so
that the clocks are correct at 8am. I'm not sure that they always
achieve this!
--
Ian