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

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. Most equipment is designed
to work at 110v - 220v (at 50 or 60Hz) look at the rating plate. That
voltage is nominal and will not include the tolerance.

Cheers

Peter

On Tue, 08 Mar 2011 09:09:02 +0000, 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.

So only 3v change, depending on the quality of you supply you may
well get a bigger fluctuantion when you drop a decent load on, say
5kW or more.

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.

They aren't spikes just norm fluctuation caused by local load
variations, either in your imdeiate vicinty or in your home. The
nominal UK voltage hasn't been 240v for years. See other post. Note
that the "harmonised" range covers the old 240v spec so nothing had
to change. The only comment I'd make about the voltage sitting at 250
odd is that incandescent light bulbs will have a much shorter life.

We used to get through 40W candles in the living room (6 in use
18hrs/day) at about one per month and other odd 60W bulbs at several
a year. Bought a UPS plugged it in and it went straight into "voltage
trim" mode I thought it was faulty! Measured the volts up at 250 or
so, reported it, men arrived in a couple of hours confirmed the
reading and came back a day or two later to adjust the tapping on our
transformer. Voltage now sits between 235 and 245 (was 245 to 255)
and incandescent light bulbs last "forever".

The post about voltage variation was probably mine from the 3rd March
wondering if the grid had had a problem as our volts had risen to 253
for quite long periods overnight 2nd/3rd. Since then things have been
with the normal 235 to 245 range.

--
Cheers
Dave.

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. Most equipment is designed
to work at 110v - 220v (at 50 or 60Hz) look at the rating plate. 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

On Tue, 08 Mar 2011 10:08:39 +0000 (GMT), "Dave Liquorice"
wrote:

The post about voltage variation was probably mine from the 3rd March
wondering if the grid had had a problem as our volts had risen to 253
for quite long periods overnight 2nd/3rd. Since then things have been
with the normal 235 to 245 range.

Last time I looked (ten minutes ago) the read-out was reading 248v.

MM

On Mar 8, 9:09*am, 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

A voltage spike is 100s of volts big, and lasts for milliseconds.

240v is the target voltage, real voltage can be 10s of volts away from
this. 1v variation isn't an issue.


NT

On Tue, 8 Mar 2011 10:27:33 +0000, Ian Jackson
wrote:

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.

I don't measure the mains voltage but I do notice fluctuations. All
the lights dim noticably in the house for a short time. It happens
fairly frequently in the early evening. It does not appear to cause
any problems to computers etc.

--
(\__/) M.
(='.'=) Due to the amount of spam posted via googlegroups and
(")_(") their inaction to the problem. I am blocking some articles
posted from there. If you wish your postings to be seen by
everyone you will need use a different method of posting.

In article ,
lid says...
I don't measure the mains voltage but I do notice fluctuations. All
the lights dim noticably in the house for a short time. It happens
fairly frequently in the early evening. It does not appear to cause
any problems to computers etc.


Nor should it - SMPS should be very tolerant of such things - after all,
they're usually considerably over rated in PC applications and only have
to up the duty-cycle briefly.

--
Skipweasel - never knowingly understood.

Tabby wrote:
On Mar 8, 9:09 am, 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

A voltage spike is 100s of volts big, and lasts for milliseconds.

240v is the target voltage, real voltage can be 10s of volts away from
this. 1v variation isn't an issue.


I'll second that and just add that unless all the supply cables are
superconductors then the voltage will vary according to the load in both MMs
house and neighbouring houses.

MM - It is not unusual for the voltage to drop by as much as 8 volts in a
house when an electric shower is switched on depending upon the external
resistance of the supply to the house.


--
Adam

On Tue, 8 Mar 2011 17:42:09 -0000, "ARWadsworth"
wrote:

Tabby wrote:
On Mar 8, 9:09 am, 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

A voltage spike is 100s of volts big, and lasts for milliseconds.

240v is the target voltage, real voltage can be 10s of volts away from
this. 1v variation isn't an issue.


I'll second that and just add that unless all the supply cables are
superconductors then the voltage will vary according to the load in both MMs
house and neighbouring houses.

MM - It is not unusual for the voltage to drop by as much as 8 volts in a
house when an electric shower is switched on depending upon the external
resistance of the supply to the house.

When I first observed the 250v this morning there was only the PC on.

MM

MM wrote:
On Tue, 8 Mar 2011 17:42:09 -0000, "ARWadsworth"
wrote:

Tabby wrote:
On Mar 8, 9:09 am, 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

A voltage spike is 100s of volts big, and lasts for milliseconds.

240v is the target voltage, real voltage can be 10s of volts away
from this. 1v variation isn't an issue.


I'll second that and just add that unless all the supply cables are
superconductors then the voltage will vary according to the load in
both MMs house and neighbouring houses.

MM - It is not unusual for the voltage to drop by as much as 8 volts
in a house when an electric shower is switched on depending upon the
external resistance of the supply to the house.

When I first observed the 250v this morning there was only the PC on.

And did you go and ask all the neighbours what they were using?

--
Adam

On Mar 8, 10:27*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. *Most equipment is designed
to work at 110v - 220v (at 50 or 60Hz) look at the rating plate. *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.

rusty

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

On Tue, 8 Mar 2011 20:34:49 +0000, Ian Jackson wrote:

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.

The frequency is very important, it's maintained at 50Hz +/- 1% ie
49.5 to 50.5 Hz nut National Grid work to an operational limit of +/-
0.4% (+/- 0.2Hz).

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!

Oh they do! Questions get asked in the house if they don't. IIRC the
last time they had to announce that mains driven clocks had the wrong
time and would need to be corrected was during the winter of 1947...

--
Cheers
Dave.

In article 3bb8952f-1316-4b1a-aaee-a773ee2fe244
@v31g2000vbs.googlegroups.com, says...
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.

Almost all LED clocks are mains synched. Since they have to be mains
powered anyway (yeah, mostly) then they're already connected to a well
regulated (by statute) frequency source.

As it happens, I have an exception, an LED clock that uses the RDS data
to set the time, though in the absence of decent reception it seems to
cope tolerably - presumably off the mains frequency or a crystal.

--
Skipweasel - never knowingly understood.

On Tue, 08 Mar 2011 21:26:01 +0000 (GMT), "Dave Liquorice"
wrote:

On Tue, 8 Mar 2011 20:34:49 +0000, Ian Jackson wrote:

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.

The frequency is very important, it's maintained at 50Hz +/- 1% ie
49.5 to 50.5 Hz nut National Grid work to an operational limit of +/-
0.4% (+/- 0.2Hz).

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!

Oh they do! Questions get asked in the house if they don't. IIRC the
last time they had to announce that mains driven clocks had the wrong
time and would need to be corrected was during the winter of 1947...

Maybe 20-30 years ago it dropped to minus 4 secs or so on one occasion
when there was a split system. It *might* have been October 1987.
Not sure if they got the clocks back to zero error at +24hours.

During winter on another occasion the frequency dropped to somewhere
in the mid to high 47's before a system split and load shedding gave a
high frequency in the north and midlands and a low one in the south.

It took a hell of a lot of work to get the two systems back in sync,
and as a consequence over the next couple of years they changed the
synchronising relays associated with a very large number of circuit
breakers across the 400kV and 275kV grid such that a second method of
automatic closure was possible dependent on slip angle and rate of
change of slip angle rather than just the slip angle. These could be
primed and left for 15mins so that if the system either side of the
breaker met the targets it would automatically close, previously the
only method was a 2 minute timer for 'perfect sync' or a manual
closure that ran the risk of exploding the breaker into copper and
porcelain shrapnel.

The long period of split running during this incident gave a clock
error such that various bits of the country were out of sync by a
second or more. None of this made the papers at the time


--

In article o.uk,
says...
The frequency is very important, it's maintained at 50Hz +/- 1% ie
49.5 to 50.5 Hz nut National Grid work to an operational limit of +/-
0.4% (+/- 0.2Hz).


There's also a close tolerance on the total number of cycles in the day,
too.

Had a quick fossick for it, but found this instead...

http://www.nationalgrid.com/uk/Elect...ncy/Freq60.htm

--
Skipweasel - never knowingly understood.

On Tue, 08 Mar 2011 22:14:39 +0000, The Other Mike
wrote:

Maybe 20-30 years ago it dropped to minus 4 secs or so on one occasion
when there was a split system. It *might* have been October 1987.
Not sure if they got the clocks back to zero error at +24hours.

During winter on another occasion the frequency dropped to somewhere
in the mid to high 47's before a system split and load shedding gave a
high frequency in the north and midlands and a low one in the south.

It took a hell of a lot of work to get the two systems back in sync,
and as a consequence over the next couple of years they changed the
synchronising relays associated with a very large number of circuit
breakers across the 400kV and 275kV grid such that a second method of
automatic closure was possible dependent on slip angle and rate of
change of slip angle rather than just the slip angle. These could be
primed and left for 15mins so that if the system either side of the
breaker met the targets it would automatically close, previously the
only method was a 2 minute timer for 'perfect sync' or a manual
closure that ran the risk of exploding the breaker into copper and
porcelain shrapnel.

The long period of split running during this incident gave a clock
error such that various bits of the country were out of sync by a
second or more. None of this made the papers at the time

Crikey, I never realised just what technology is needed to provide a
country with an electricity grid!

MM

On Tue, 8 Mar 2011 18:16:14 -0000, "ARWadsworth"
wrote:

MM wrote:
On Tue, 8 Mar 2011 17:42:09 -0000, "ARWadsworth"
wrote:

Tabby wrote:
On Mar 8, 9:09 am, 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

A voltage spike is 100s of volts big, and lasts for milliseconds.

240v is the target voltage, real voltage can be 10s of volts away
from this. 1v variation isn't an issue.


I'll second that and just add that unless all the supply cables are
superconductors then the voltage will vary according to the load in
both MMs house and neighbouring houses.

MM - It is not unusual for the voltage to drop by as much as 8 volts
in a house when an electric shower is switched on depending upon the
external resistance of the supply to the house.

When I first observed the 250v this morning there was only the PC on.

And did you go and ask all the neighbours what they were using?

Well, no!

MM

Dave Liquorice wrote:

Oh they do! Questions get asked in the house if they don't. IIRC the
last time they had to announce that mains driven clocks had the wrong
time and would need to be corrected was during the winter of 1947...

Back in the late 60s, I spent some time at Eggborough power
station. There was an interesting clock on the wall of the
control room. It clearly had two inputs - one was from the
station mains frequency which was driving its second hand (can't
remember if there were actually any others) forward, whilst it
was driven backwards by the station instrumentation feed, from a
pendulum clock which produced pulses ever second (and minute,
quarter hour etc for various printing recorders).

So the hand moved around the dial, twitching back every second,
generally hovered around 12 o'clock, but did move around a little
over time.

Chris
--
Chris J Dixon Nottingham UK


Have dancing shoes, will ceilidh.

In message , MM
writes
On Tue, 08 Mar 2011 22:14:39 +0000, The Other Mike
wrote:

Maybe 20-30 years ago it dropped to minus 4 secs or so on one occasion
when there was a split system. It *might* have been October 1987.
Not sure if they got the clocks back to zero error at +24hours.

During winter on another occasion the frequency dropped to somewhere
in the mid to high 47's before a system split and load shedding gave a
high frequency in the north and midlands and a low one in the south.

It took a hell of a lot of work to get the two systems back in sync,
and as a consequence over the next couple of years they changed the
synchronising relays associated with a very large number of circuit
breakers across the 400kV and 275kV grid such that a second method of
automatic closure was possible dependent on slip angle and rate of
change of slip angle rather than just the slip angle. These could be
primed and left for 15mins so that if the system either side of the
breaker met the targets it would automatically close, previously the
only method was a 2 minute timer for 'perfect sync' or a manual
closure that ran the risk of exploding the breaker into copper and
porcelain shrapnel.

The long period of split running during this incident gave a clock
error such that various bits of the country were out of sync by a
second or more. None of this made the papers at the time

Crikey, I never realised just what technology is needed to provide a
country with an electricity grid!

A long time ago, one of my set lab experiments was to run up fairly
large three-phase generator, synchronise it with the mains, get it
generating power and do various test measurements. Fortunately, my
professional career was more concerned with valves and transistors, and
I never needed to do it again!
--
Ian

MM wrote:
On Tue, 8 Mar 2011 18:16:14 -0000, "ARWadsworth"
wrote:
I'll second that and just add that unless all the supply cables are
superconductors then the voltage will vary according to the load in
both MMs house and neighbouring houses.

MM - It is not unusual for the voltage to drop by as much as 8
volts in a house when an electric shower is switched on depending
upon the external resistance of the supply to the house.

When I first observed the 250v this morning there was only the PC
on.

And did you go and ask all the neighbours what they were using?

Well, no!

Well there you are. Short of logging all the neighbours supplies you will
never know who turned on or off their electical devices:-)

Your electricity supply is normal.

Cheers
--
Adam

On Tue, 8 Mar 2011 17:18:17 -0000, Skipweasel
wrote:

In article ,
says...
I don't measure the mains voltage but I do notice fluctuations. All
the lights dim noticably in the house for a short time. It happens
fairly frequently in the early evening. It does not appear to cause
any problems to computers etc.

Nor should it - SMPS should be very tolerant of such things - after all,
they're usually considerably over rated in PC applications and only have
to up the duty-cycle briefly.

I was using this more as an indication of how long the light dimmed
for ;-) I am more interested if there is a problem with the supply.
--
(\__/) M.
(='.'=) Due to the amount of spam posted via googlegroups and
(")_(") their inaction to the problem. I am blocking some articles
posted from there. If you wish your postings to be seen by
everyone you will need use a different method of posting.

On Mar 8, 10:27*pm, Skipweasel
wrote:
In article o.uk,
says...

The frequency is very important, it's maintained at 50Hz +/- 1% ie
49.5 to 50.5 Hz nut National Grid work to an operational limit of +/-
0.4% (+/- 0.2Hz).

There's also a close tolerance on the total number of cycles in the day,
too.

Had a quick fossick for it, but found this instead...

http://www.nationalgrid.com/uk/Elect...ncy/Freq60.htm

Surprised no one has posted this yet http://www.dynamicdemand.co.uk/grid.htm

MBQ

In message
on Wed, 9 Mar 2011 02:19:24 -0800 (PST)
Man at B&Q wrote:

On Mar 8, 10:27Â*pm, Skipweasel
wrote:
In article o.uk,
says...

The frequency is very important, it's maintained at 50Hz +/- 1% ie
49.5 to 50.5 Hz nut National Grid work to an operational limit of +/-
0.4% (+/- 0.2Hz).

There's also a close tolerance on the total number of cycles in the day,
too.

Had a quick fossick for it, but found this instead...

http://www.nationalgrid.com/uk/Elect...ncy/Freq60.htm

Surprised no one has posted this yet http://www.dynamicdemand.co.uk/grid.htm


This site shows lots of useful info on one page:

http://www.bmreports.com/bsp/bsp_home.htm

--

Terry

On 9 Mar,
Chris J Dixon wrote:

Dave Liquorice wrote:

Oh they do! Questions get asked in the house if they don't. IIRC the
last time they had to announce that mains driven clocks had the wrong
time and would need to be corrected was during the winter of 1947...

Back in the late 60s, I spent some time at Eggborough power
station. There was an interesting clock on the wall of the
control room. It clearly had two inputs - one was from the
station mains frequency which was driving its second hand (can't
remember if there were actually any others) forward, whilst it
was driven backwards by the station instrumentation feed, from a
pendulum clock which produced pulses ever second (and minute,
quarter hour etc for various printing recorders).

So the hand moved around the dial, twitching back every second,
generally hovered around 12 o'clock, but did move around a little
over time.

Mains driven clocks are allowed to drift off by so many seconds a day. Before
privatisation it was kept very close to zero, but needed to catch up (or
even anticipate future slow running) at night. Since then the full range of
drift has been more likely to occur. If memory serves (probably not) the
legal requirement was about 30 seconds.

The clock will have been to show the difference. We had seperate clocks at
work which showed the difference.

--
B Thumbs
Change lycos to yahoo to reply

wrote:
On 9 Mar,
Chris J Dixon wrote:

Dave Liquorice wrote:

Oh they do! Questions get asked in the house if they don't. IIRC the
last time they had to announce that mains driven clocks had the wrong
time and would need to be corrected was during the winter of 1947...
Back in the late 60s, I spent some time at Eggborough power
station. There was an interesting clock on the wall of the
control room. It clearly had two inputs - one was from the
station mains frequency which was driving its second hand (can't
remember if there were actually any others) forward, whilst it
was driven backwards by the station instrumentation feed, from a
pendulum clock which produced pulses ever second (and minute,
quarter hour etc for various printing recorders).

So the hand moved around the dial, twitching back every second,
generally hovered around 12 o'clock, but did move around a little
over time.

Mains driven clocks are allowed to drift off by so many seconds a day. Before
privatisation it was kept very close to zero, but needed to catch up (or
even anticipate future slow running) at night. Since then the full range of
drift has been more likely to occur. If memory serves (probably not) the
legal requirement was about 30 seconds.

The clock will have been to show the difference. We had seperate clocks at
work which showed the difference.

That's short term. I believe that over a day, the grid has to average to
spot on.

The shortfall is generally made up at night when demand is low, and all
the pumped storage has been replenished.

In article , MM
writes

Crikey, I never realised just what technology is needed to provide a
country with an electricity grid!

There was an excellent series (of 3 programmes) called the Secret Life
of the National Grid shown before Christmas. You may be able to find it
with the BBC iPlayer.

--
Mike Tomlinson

On Mar 9, 2:23*pm, Mike Tomlinson wrote:
In article , MM
writes

Crikey, I never realised just what technology is needed to provide a
country with an electricity grid!

There was an excellent series (of 3 programmes) called the Secret Life
of the National Grid shown before Christmas. *You may be able to find it
with the BBC iPlayer.

Well, it was a bit lacking in real technical content.

MBQ

In article ,
lid says...
I was using this more as an indication of how long the light dimmed
for ;-) I am more interested if there is a problem with the supply.


Doesn't sound it - what you're describing is how electricity is in most
parts of the country - particularly in the countriside.

--
Skipweasel - never knowingly understood.

On Tue, 08 Mar 2011 22:14:39 +0000, The Other Mike
wrote:

During winter on another occasion the frequency dropped to somewhere
in the mid to high 47's

Make that 48's!

--

On Tue, 8 Mar 2011 10:27:33 +0000, Ian Jackson wrote:


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.

Routine load shedding, it's been happening for decades. 5% then 10% load
shed, acheived by a voltage reduction, I'll let you work out the percentage
reduction in voltage to get the reduction in load.

After that it's rota disconnection as happened in the 1970s.


--
The Wanderer

Computers are incredibly fast, accurate, and stupid;
humans are incredibly slow, inaccurate and brilliant;
together they are powerful beyond imagination.

The Wanderer wrote:
On Tue, 8 Mar 2011 10:27:33 +0000, Ian Jackson wrote:


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.

Routine load shedding, it's been happening for decades. 5% then 10% load
shed, acheived by a voltage reduction, I'll let you work out the percentage
reduction in voltage to get the reduction in load.

After that it's rota disconnection as happened in the 1970s.


Yep. Think of the grid as a huge generators to which lots of little
engines are geared. As demand goes up the voltage and frequency start to
fall..the whole contraption is 'climbing a hill'

Throttles are opened on all the engines online, and new ones are geared
to it to help a bit. Meanwhile the word goes out for anyone who can do
without the grid to get off it, and if anyone has any backup power units
spare, could they please start them..


If the whole shebang cant make it over the top, then passengers are
thrown out till it can.

You will get far more familiar with this as more silly wind power is
added to the grid.

On Thu, 10 Mar 2011 11:31:59 +0000, The Natural Philosopher wrote:

You will get far more familiar with this as more silly wind power is
added to the grid.

I'm not overly keen on this frequency based automatic load shedding
(as in switching off) either. Sounds like a recipe for grid
instabilty if you ask me. Frequency drops, lots of stuff drops off
line, Whe Hey! too much capacity frequency goes up, stuff comes back
online, frequency drops...

And how much stuff is about that can be switched off for an
indeterminate period without warning? Not a lot, storage heaters
maybe but they aren't on when there is peak demand and you could only
switch 'em off for a limited period otherwise people would be
cold(er) the next evening.

Some form of dynamic load directly controlled by the grid would work
but I'm skeptical about an open loop system.

--
Cheers
Dave.

Dave Liquorice wrote:
On Thu, 10 Mar 2011 11:31:59 +0000, The Natural Philosopher wrote:

You will get far more familiar with this as more silly wind power is
added to the grid.

I'm not overly keen on this frequency based automatic load shedding
(as in switching off) either. Sounds like a recipe for grid
instabilty if you ask me. Frequency drops, lots of stuff drops off
line, Whe Hey! too much capacity frequency goes up, stuff comes back
online, frequency drops...


No, that's not a problem really..as there are time delays and hysteresis
built in.

But the whole thing is pretty silly really as the amount of kit that can
be load dumped in this way is probably vanishingly small.




And how much stuff is about that can be switched off for an
indeterminate period without warning?

Exactly.

Not a lot, storage heaters
maybe but they aren't on when there is peak demand and you could only
switch 'em off for a limited period otherwise people would be
cold(er) the next evening.

Some form of dynamic load directly controlled by the grid would work
but I'm skeptical about an open loop system.


Actually it isn't open loop, the feedback control is in the frequency.


I am very mixed about this, On the one hand its a small effect, and wont
save the planet, on the other hand its actually bloody simple and cheap
to build into - say a fridge freezer - the intelligence to do it and
to move the largest part of that load to off peak times.

Probably a far fare better way to modulate demand, would be for people
to work 24x7, preferably from home, and spread the 'human activity' part
of the load throughout the night as well as the day..

Frankly this is just another bit of 'this will help a teeny bit, but
such a teeny bit its barely worth spending money on' like switching off
the telly at night, that's been blown up to 'This will save the planet'
by the eco-fantasists and the 'green' big business interests.

"Dave Liquorice" wrote in message ll.co.uk...
On Thu, 10 Mar 2011 11:31:59 +0000, The Natural Philosopher wrote:

You will get far more familiar with this as more silly wind power is
added to the grid.

I'm not overly keen on this frequency based automatic load shedding
(as in switching off) either. Sounds like a recipe for grid
instabilty if you ask me. Frequency drops, lots of stuff drops off
line, Whe Hey! too much capacity frequency goes up, stuff comes back
online, frequency drops...

And how much stuff is about that can be switched off for an
indeterminate period without warning?

I suspect that in the average household, not a lot but I have a friend who works for a water company and they regularly get paid for NOT pumping at certain times.

Tim

Tim Downie wrote:
"Dave Liquorice" wrote in message ll.co.uk...
On Thu, 10 Mar 2011 11:31:59 +0000, The Natural Philosopher wrote:

You will get far more familiar with this as more silly wind power is
added to the grid.
I'm not overly keen on this frequency based automatic load shedding
(as in switching off) either. Sounds like a recipe for grid
instabilty if you ask me. Frequency drops, lots of stuff drops off
line, Whe Hey! too much capacity frequency goes up, stuff comes back
online, frequency drops...

And how much stuff is about that can be switched off for an
indeterminate period without warning?

I suspect that in the average household, not a lot but I have a friend who works for a water company and they regularly get paid for NOT pumping at certain times.


He must work at Dinorwig :-)

Whilst there are a few industrial processes that are not critical when
they use power, by and large electricity is currently (sic!) used
BECAUSE it is always there, always on tap, when you need it.

"The train at platform five will be leaving when a squall hits the outer
Hebrides, and we can suck enough power off the grid to get it going, or
when everyone has finished watching Corrie, whichever is the soonest"



Tim

On Thu, 10 Mar 2011 13:38:50 +0000 (GMT), "Dave Liquorice"
wrote:

On Thu, 10 Mar 2011 11:31:59 +0000, The Natural Philosopher wrote:

You will get far more familiar with this as more silly wind power is
added to the grid.

I'm not overly keen on this frequency based automatic load shedding
(as in switching off) either. Sounds like a recipe for grid
instabilty if you ask me. Frequency drops, lots of stuff drops off
line, Whe Hey! too much capacity frequency goes up, stuff comes back
online, frequency drops...

It doesn't work like that.

If the frequency drops then the first response is the governors on all
the generators on the system. They will always actively control the
energy input such that the frequency is maintained at the target of
50Hz.

If the frequency still drops then load that is on a disconnection
agreement is removed in a controlled manner. This is usually
commercial heating / cooling / non critical processes.

Then there is voltage reduction in a number of stages to further
reduce load that isn't on a disconnection agreement (most domestic
load for instance)

If the frequency drops further then load gets shed in defined blocks
it could be an entire city, or an area , or a particularly large
industrial user - that load then stays off, there is no automatic
reconnection.

If by this stage the frequency is still dropping then the generators
automatically disconnect to protect themselves.

The grid is then dead.

Then sometime later certain contracted for 'black start' sites
commence generation.

Starting with a diesel generator, to power the fuel pumps etc to run
up a gas turbine (kerosine fueled) which then runs the auxiliaries to
run the main generation at that particular site (usually coal but
could be gas or oil) You might get some hydro running too.

Once part of the grid is energised it is interconnected with other
generation and load, controlling generation and load such that the
frequency and voltage is within limits. Gradually everything is
reconnected.

What happens at each stage is defined in advance, as are the frequency
targets (beyond the published +/- 0.5Hz) and the voltage reductions.
Consumers on a disconnection agreement know that they could be
disconnected at little or no notice.


--

On Thu, 10 Mar 2011 17:09:04 +0000, The Other Mike wrote:


If the frequency still drops then load that is on a disconnection
agreement is removed in a controlled manner. This is usually
commercial heating / cooling / non critical processes.

Then there is voltage reduction in a number of stages to further
reduce load that isn't on a disconnection agreement (most domestic
load for instance)

Two stages, as I said earlier, 5% and then 10%. Carried out very easily
these days with the automated control systems in use. It's worth noting,
however, that the load reduction is usually carried out by the Distribution
companies through their control rooms.

If the frequency drops further then load gets shed in defined blocks
it could be an entire city, or an area , or a particularly large
industrial user - that load then stays off, there is no automatic
reconnection.

Unlikely to be a whole city, unless it's an emergency load shed. Normally
the rota disconnections are planned on an 11kv feeder by feeder basis,
again carried out these days by a simple command from a central control
room. I disagree with your comment that there's no automatic reconnection,
rota shedding is usually for 3 hour periods.

If we're talking emergency load shedding, that usually implies something
catastrophic has happened, eith on the generation or transmission systems.
I seem to recollect it happened some years ago during summer, when part of
the grid was out for maintenance and there was another failure on either a
275 or 400kv cable somewhere around north London meaning effectively that
the country was electricaslly split in two. Lasted for several hours if
memory serves correctly.

Let's also be fair though, for the conditions you mention we are talking an
absolute catastrophe. That we don't get therm is why control engineers
suffer high blood pressure.....

BTDTGTTS.

--
The Wanderer

I cannot teach anybody anything, I can only make them think. ~Socrates

In article o.uk,
says...
And how much stuff is about that can be switched off for an
indeterminate period without warning?


Fridge, freezer, washing machine etc. Even if they're only swapped to a
lower duty cycle - say ten minutes off in an hour, that may well be
enough to tide over the demand peak.

--
Skipweasel - never knowingly understood.