UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > General Vintage Technology > General Vintage Technology Discussions

Notices

General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc.

Closed Thread
 
Thread Tools
Old 7th Mar 2018, 9:23 pm   #41
Andrew2
Octode
 
Join Date: Mar 2010
Location: Dukinfield, Cheshire, UK.
Posts: 1,486
Default Re: Electric clocks running slow warning

I saw a very interesting documentary on the Grid a year or two back (and I think we may have discussed it on here) and I'm sure one of the interviewees said that averaged over a 24 hr (?) period, the frequency HAD to be 50 Hz. So if it dropped below 50 Hz for a period, it was then sped up to above 50 Hz for the same period, thus averaging 50 Hz to keep synchronous clocks on time.
Of course if demand is so heavy that they cannot speed up then they just can't do it I suppose.
__________________
Andy G1HBE.
Andrew2 is offline  
Old 7th Mar 2018, 9:51 pm   #42
tealandsilver
Tetrode
 
Join Date: Nov 2017
Location: East Lothian, Scotland, UK.
Posts: 64
Default Re: Electric clocks running slow warning

Andrew, yes, I remember that one, although the requirement for an average over the 24hr period I wasn't aware of.

Here's another shorter video

https://www.youtube.com/watch?v=UTM2Ck6XWHg
tealandsilver is offline  
Old 7th Mar 2018, 10:10 pm   #43
broadgage
Octode
 
Join Date: Jan 2010
Location: North Somerset, UK.
Posts: 1,354
Default Re: Electric clocks running slow warning

Quote:
Originally Posted by hannahs radios View Post
There was one day Friday I think when the OCGT plant was run all day this is as Paul says unusual. I also notice that other gas generation was throttled back because of the gas shortage and the fact that the price of gas was the highest it's been all winter. The French link was running at less than full capacity for at least 2 days. I think really the grid coped well all things considered. Incidentally highest consumption was just over 50,000 Megawatts that's a LOT of electricity.
I observed that, and my suspicion is that the OCGT plant was at the time burning light distillate oil and not natural gas.
I can't see why at a time of gas scarcity, that relatively inefficient OCGT plant would be run for many hours, whilst more efficient CCGT plant was idle.

It may have been preferable to burn oil at relatively low efficiency rather than to burn gas at greater efficiency.
broadgage is offline  
Old 7th Mar 2018, 10:30 pm   #44
tealandsilver
Tetrode
 
Join Date: Nov 2017
Location: East Lothian, Scotland, UK.
Posts: 64
Default Re: Electric clocks running slow warning

Unfortunately it has less to do with efficiency, more to do with the bid price that the generator has submitted into the trading system. There are can be other reasons why a generator will run more expensive plant such as outage requirements, proving runs, statutory tests etc.
tealandsilver is offline  
Old 7th Mar 2018, 10:34 pm   #45
high_vacuum_house
Octode
 
high_vacuum_house's Avatar
 
Join Date: May 2003
Location: Rugby (home) and all over the country for work
Posts: 1,092
Smile Re: Electric clocks running slow warning

Last week we ran all of our gas and Diesel engines every day. The buy price for electricity went very high and on one of the days we ran them for 17 hours continuously. We certainly got through a lot of diesel!! (Approximately 100,000 litres!!) The grid frequency is the same all over the UK and all of the rotating alternators speed is governed by the grid frequency as they are all synchronous machines.

The national grid have to be very careful about the maximum and minimum frequency as well as the rate of change of frequency as all of our STOR power generation sites have protection relays called G59 which will trip the site offline should the frequency deviation go outside the prescribed limits. This is to prevent a situation called island mode where the power station can continue generating into the local grid when the power is cut to the local substation. This could cause a sudden voltage and frequency increase damaging equipment or making equipment being worked on live that should be dead.

The grid frequency is constantly changing slightly as demand and generation change throughout the day. The slightest increase in load slows it down whereas a slight increase in generation increases frequency. It is a fine balance to keep it as close to 50hz as possible.

Christopher Capener
__________________
A proper radio is one that needs to be moved with a wheelbarrow !!
high_vacuum_house is online now  
Old 7th Mar 2018, 11:08 pm   #46
tealandsilver
Tetrode
 
Join Date: Nov 2017
Location: East Lothian, Scotland, UK.
Posts: 64
Default Re: Electric clocks running slow warning

This may illustrate some of the reasons. I assume that there is a similar scheme in place for this year. Towards the end of my career in the industry I had noticed that the numbers of "Notification of Inadequate System Margins" (NISM's) had gone from zero in the 2000's to 3 or 4 a year by the time I retired in 2013. This has frightened the Government into action!

https://www.theguardian.com/environm...this-christmas
tealandsilver is offline  
Old 8th Mar 2018, 12:02 am   #47
McMurdo
Dekatron
 
McMurdo's Avatar
 
Join Date: Jun 2009
Location: Staffordshire Moorlands, UK.
Posts: 3,590
Default Re: Electric clocks running slow warning

I saw that documentary, if it was the same one, from the national grid control centre. Lots of LCD monitors and guys in shirt & tie scanning the tv schedules and keeping an eye on the big LED frequency meter. At one point the chappie told the reporter he'd have to 'bring another power station online soon' as the frequency was getting too low; apparently the drop was a good indicator of more power needed.

I assume power generation works in a similar way to other supply & demand systems (such as compressed air) where there's a hardcore of bulk supply for coarse adjustments and then a smaller, more easily variable set of generators that take up the slack to fine tune everything up or down.
__________________
Kevin
McMurdo is offline  
Old 8th Mar 2018, 12:18 am   #48
tealandsilver
Tetrode
 
Join Date: Nov 2017
Location: East Lothian, Scotland, UK.
Posts: 64
Default Re: Electric clocks running slow warning

Good way of looking at it, the hardcore or base load stations being the nuclear fleet and to an extent coal and gas fired stations. If you look at the monthly graphs on the link below you will see the variance in energy supplies.

http://www.gridwatch.templar.co.uk/
tealandsilver is offline  
Old 8th Mar 2018, 12:27 am   #49
g8jzyian
Pentode
 
Join Date: Jan 2009
Location: Liverpool, Merseyside, UK.
Posts: 111
Default Re: Electric clocks running slow warning

In the late 70's we had a differential time indicator in the grid control room.
Basically a synchronous clock and a gents pulse clock both feeding to a differential gear with an indicator. the control room staff tried to keep the error below 1 min per day if I remember correctly (long time ago)

Ian
g8jzyian is offline  
Old 8th Mar 2018, 2:30 am   #50
cheerfulcharlie
Heptode
 
Join Date: May 2009
Location: Birmingham, West Midlands, UK.
Posts: 544
Default Re: Electric clocks running slow warning

We are led to believe that time is this wondrous thing holding together the universe and that if we reach the speed of light we can go back and forth in time etc.. but I think these events just prove that time is bunk...a figment of the human imagination based on mechanical observations, first of the Earth going around the Sun and then invention of the clock, photograph etc. If the mother of all clocks-the most accurate clock in the world breaks down. What do we measure as the point for starting it up again? There is nothing in nature, we have to make it up.
cheerfulcharlie is offline  
Old 8th Mar 2018, 6:09 am   #51
Radio Wrangler
Dekatron
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 12,483
Default Re: Electric clocks running slow warning

Quote:
Originally Posted by Nymrod121 View Post
There were three sets and it had to be 'got right' on the Synchroscope - any discrepancy and the relevant set's ACB would trip ... followed by remedial action which included the duty Senior Tx Eng promptly adminstering a firm kick up the TE's backside
[Best quality 'uddersfield accent: ON]

Eeeee! Tha had a proper synchroscope, not just three light bulbs? Luxury, lad!

For those that don't already know, you can see grid frequency, loading and sources data here:

http://www.gridwatch.templar.co.uk

The national grid is completely synchronised (except for a major disaster scale fault) so a mechanical analogy would be a drive shaft connecting all generators and all loads. If generation can't make the load demands, the RPM (frequency) drops, and consequentially the voltage drops which gives less power to SOME loads. Low frequency triggers some spare generating capacity into action, much lower frequency and more expensive generators are brought on-line. The grid frequency is both an indicator of the availability versus demand balance, and it is the command structure.

Switch-mode PSUs in loads don't reduce power demand when the supply voltage falls, they increase demanded current to compensate. This increases ohmic losses, drops their supply volts a bit and then compensate for that with even more current demand, so their power demand increases with falling supply volts, creating a destabilising influence.

The drive for energy saving has meant more SMPS, more 'smart motors' and has given us a less-stable network, add in wind fluctuations and the quality of our supply is less than it used to be.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline  
Old 8th Mar 2018, 7:08 am   #52
broadgage
Octode
 
Join Date: Jan 2010
Location: North Somerset, UK.
Posts: 1,354
Default Re: Electric clocks running slow warning

To add to the points already made regarding frequency control, any sudden and severe drop in frequency also triggers the automatic starting of gas turbine and diesel generating plant.
If the frequency remains low, then areas are automatically blacked out by frequency relays in substations.
Such drastic measures are only taken if the grid frequency drops to about 48.8 cycles, well below the normal lower limit of 49.5 cycles.

IIRC this last happened some years ago and resulted in large scale but brief power cuts. There was nothing exceptional about demand at the time, the problem was caused by the almost simultaneous tripping of two large generating units.
The frequency remained below the legal limit of 49.5 cycles for about 10 minutes.
The national grid are required to have a margin to cover for the largest reasonably foreseeable failure, but if two failures occur at almost the same time, not much can be done.
broadgage is offline  
Old 8th Mar 2018, 9:04 am   #53
percival007
Heptode
 
percival007's Avatar
 
Join Date: May 2005
Location: Oxfordshire, UK.
Posts: 714
Default Re: Electric clocks running slow warning

Just FYI...............

http://www.dynamicdemand.co.uk/grid.htm

James.
percival007 is offline  
Old 8th Mar 2018, 12:35 pm   #54
Goldie99
Heptode
 
Join Date: Jul 2014
Location: Boston, Lincolnshire, UK.
Posts: 544
Default Re: Electric clocks running slow warning

Am I right in assuming these frequency variations, at this order of magnitude, are also sufficient to noticeably(*) impact the speed of AC synchronous drive turntables, e.g., a Linn LP-12 (pre-Valhalla) ?

(*) By noticeably, I mean audibly.
Goldie99 is online now  
Old 8th Mar 2018, 1:48 pm   #55
Herald1360
Dekatron
 
Herald1360's Avatar
 
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 13,551
Default Re: Electric clocks running slow warning

A semitone is about a 6% frequency change, so 2% or 1 Hz in 50Hz might well be audible- especially if it happened during a sustained note in a musical piece.

The fat lady's voice might wobble a bit!
__________________
....__________
....|____||__|__\_____
.=.| _---\__|__|_---_|.
.........O..Chris....O
Herald1360 is offline  
Old 8th Mar 2018, 1:58 pm   #56
broadgage
Octode
 
Join Date: Jan 2010
Location: North Somerset, UK.
Posts: 1,354
Default Re: Electric clocks running slow warning

I suspect that most listeners would not notice most frequency disturbances, but yes a keen listener would notice bad mains frequency variations.

In years gone by, cinema projectors were tied to the line frequency, and cinema staff with a good watch or clock could just about detect that the actual running time of a film could vary by a minute or so.
broadgage is offline  
Old 8th Mar 2018, 2:06 pm   #57
Andrew2
Octode
 
Join Date: Mar 2010
Location: Dukinfield, Cheshire, UK.
Posts: 1,486
Default Re: Electric clocks running slow warning

Quote:
Originally Posted by cheerfulcharlie View Post
We are led to believe that time is this wondrous thing holding together the universe and that if we reach the speed of light we can go back and forth in time etc.. but I think these events just prove that time is bunk...a figment of the human imagination based on mechanical observations, first of the Earth going around the Sun and then invention of the clock, photograph etc. If the mother of all clocks-the most accurate clock in the world breaks down. What do we measure as the point for starting it up again? There is nothing in nature, we have to make it up.
Quite right - we must all bear in mind that God invented time to prevent everything happening at once!
Who was it that said that?
__________________
Andy G1HBE.
Andrew2 is offline  
Old 8th Mar 2018, 3:16 pm   #58
kalee20
Dekatron
 
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 5,098
Default Re: Electric clocks running slow warning

Quote:
Originally Posted by broadgage View Post
In years gone by, cinema projectors were tied to the line frequency, and cinema staff with a good watch or clock could just about detect that the actual running time of a film could vary by a minute or so.
Only approximately. Often, induction motors were used, and these have 'slip' so only loosely tied. And the projector mechanism may be belt-driven too, another opportunity for slip.

However, assuming these are constant, yes a small frequency change in the mains could still manifest itself in a minute or so variation in duration.

I recall Adrian Hope (Barry Fox) in an article, pointing out that crystal-locked turntable motors might actually be unnecessarily more accurate than the records they would be playing, as recording lathes were driven by off-line AC motors so could vary by the supply frequency.


Quote:
Originally Posted by Andrew2 View Post
...we must all bear in mind that God invented time to prevent everything happening at once!
Who was it that said that?
Dunno! But He did a good job, time (or frequency) is the quantity which we've been able to measure with the best precision of anything!
kalee20 is offline  
Old 8th Mar 2018, 3:27 pm   #59
merlinmaxwell
Dekatron
 
merlinmaxwell's Avatar
 
Join Date: Jul 2008
Location: Maidenhead, Berkshire, UK.
Posts: 8,431
Default Re: Electric clocks running slow warning

Mains clock 3 minutes slow, I wonder if they will insert cycles to correct it when the load goes down?
__________________
Cats have staff, it's dogs that have owners.
merlinmaxwell is offline  
Old 8th Mar 2018, 3:34 pm   #60
barrymagrec
Heptode
 
Join Date: Dec 2017
Location: Morden, Surrey, UK.
Posts: 560
Default Re: Electric clocks running slow warning

Quote:
Originally Posted by Goldie99 View Post
Am I right in assuming these frequency variations, at this order of magnitude, are also sufficient to noticeably(*) impact the speed of AC synchronous drive turntables, e.g., a Linn LP-12 (pre-Valhalla) ?

(*) By noticeably, I mean audibly.
I`d be very surprised, prior to circa 1970 most broadcast tape machines used mains synchronous capstan motors and I don`t remember anyone suggesting a problem - the broadcast spec for speed stability was +/- 0.2% or about 3.6 seconds an hour, this was measured assuming correct mains frequency but even so much more speed error would have played havoc with programme timings, crashing the pips and so on.

Any variation in mains frequency is likely to be quite slow so not easily heard.

Also bear in mind that TV runs 24 fps feature films at 25 fps so more than 4% fast yet no one seems to notice.
barrymagrec is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 10:25 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Copyright ©2002 - 2019, Paul Stenning.