Hi gang,

AIUI, out in the road there are three live wires and one neutral. The phases of the lives are 120 degrees out of phase with one another. The potential difference between any two live wires is 440V. The potential difference between any live and neutral is 230V. Domestic supplies only tap one live and the neutral to give you a single phase supply, so if you want a 3 phase supply for a workshop or whatever, you have to get the leccy blokes in to dig up the road and tap you into one of the other live wires. Do I have that right?

cheers.

Oh, and before some helpful soul offers up a practical solution, such as "get yerself a phase converter, mate, it's a lot cheaper" I should just point out that I'm NOT looking for solutions, here, I'm simply enquiring as to whether my understanding of the basic situation is correct or not. Thanks!

On Sun, 7 Jul 2013 06:03:20 -0700 (PDT),
wrote:

Oh, and before some helpful soul offers up a practical solution, such as "get yerself a phase converter, mate, it's a lot cheaper" I should just point out that I'm NOT looking for solutions, here, I'm simply enquiring as to whether my understanding of the basic situation is correct or not. Thanks!

From a legal, technical or practical angle?

AB

On Sunday, 7 July 2013 15:08:12 UTC+2, Archibald wrote:
On Sun, 7 Jul 2013 06:03:20 -0700 (PDT),

wrote:



Oh, and before some helpful soul offers up a practical solution, such as "get yerself a phase converter, mate, it's a lot cheaper" I should just point out that I'm NOT looking for solutions, here, I'm simply enquiring as to whether my understanding of the basic situation is correct or not. Thanks!



From a legal, technical or practical angle?



AB

Er, technical and theoretical. I'm already aware that the most cost-effective practical solution is to hook up a phase converter to the distribution board via its own spur and that's what I'll probably end up doing.

On Sun, 7 Jul 2013 05:59:03 -0700 (PDT),
wrote:

Hi gang,

AIUI, out in the road there are three live wires and one neutral. The phases of the lives are 120 degrees out of phase with one another. The potential difference between any two live wires is 440V. The potential difference between any live and neutral is 230V. Domestic supplies only tap one live and the neutral to give you a single phase supply, so if you want a 3 phase supply for a workshop or whatever, you have to get the leccy blokes in to dig up the road and tap you into one of the other live wires. Do I have that right?

No good tapping into just one of the other live wires you need two
more.

Five wires in total

L1
L2
L3
N
E

Plus a new three phase meter (or another two single phase ones)

and a big hole in your bank account

wrote:
On Sunday, 7 July 2013 15:08:12 UTC+2, Archibald wrote:
On Sun, 7 Jul 2013 06:03:20 -0700 (PDT),

wrote:



Oh, and before some helpful soul offers up a practical solution, such as "get yerself a phase converter, mate, it's a lot cheaper" I should just point out that I'm NOT looking for solutions, here, I'm simply enquiring as to whether my understanding of the basic situation is correct or not. Thanks!



From a legal, technical or practical angle?



AB

Er, technical and theoretical. I'm already aware that the most cost-effective practical solution is to hook up a phase converter to the distribution board via its own spur and that's what I'll probably end up doing.

I don't really see any 'legal' angle provided the leecy board or their
agents does the work.
In addition to the cabling, you will need a change of meter and
distribution board.
I doubt that they will want to balance the loads for domestic use so
your main house load can stay on one phase and the three phase go off to
your workshop etc
When selecting your wiring to the 3 phase load, you may want to run a
neutral as well because some machines use the neutral for control
circuits. Latest machines tend to use a 440-110 or a 440-24 transformer
for controls. If you are buying secondhand stuff, my suggestion would be
to be prepared with a neutral too.

Incidentally if you go down either the converter or inverter route, you
might find this of interest.
http://homepage.ntlworld.com/bob.min...-%20Issue2.pdf

Some converters will use the single phase neutral as one of the output
phases thus not providing a neutral in the correct relationship to the
other phases.
Inverters will usually only provide 3 phase output at the same voltage
as the input. i.e. run from 240v single phase will only produce 240v
three phase output so motors in your machines need to be dual voltage -
marked as 240/440v or similar.

hth

Bob

It's curious. I've been heavily into electronics for decades yet nothing I've learned it seems, is relevant to domestic/industrial electric installations.
Though I'm intimately acquainted with the concept of phase, phase-shift and know the difference between current, voltage and power inside-out I'm still struggling to get to grips with this 'macro' stuff. These two fields are like chalk and cheese. I suppose an electrician would be equally perplexed if required to calculate the output impedance of a buffer/current-amplifier stage. :-/

wrote :
Hi gang,

AIUI, out in the road there are three live wires and one neutral. The phases
of the lives are 120 degrees out of phase with one another. The potential
difference between any two live wires is 440V. The potential difference
between any live and neutral is 230V. Domestic supplies only tap one live and
the neutral to give you a single phase supply, so if you want a 3 phase
supply for a workshop or whatever, you have to get the leccy blokes in to dig
up the road and tap you into one of the other live wires. Do I have that
right?

cheers.

The basic numbers in the UK are 415v 3Ph. 240v single phase = 240v from
any of the three phases, to neutral. 415v as measured from any phase
aay of the other two.

If you have 1ph + N, you are lacking two more phases to make a 3ph
supply.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

I mean they're clearly two different disciples entirely. In my typically millivolt/milliamp world, we don't have to contend with forces sufficient to rip a machine's internals to pieces as you do with power engineering, so the need for nice, smooth 3 phase supplies simply doesn't arise in the first place!

Right, Harry. So with only two live phases you'd have your 415V potential difference alright, but it would be effectively unusable?

On 07/07/2013 15:30, Harry Bloomfield wrote:
....
The basic numbers in the UK are 415v 3Ph. 240v single phase = 240v from
any of the three phases, to neutral. 415v as measured from any phase aay
of the other two....

Since 2003, it has been 400v and 230v, but with wider tolerances, so
that neither we nor any other EU country had to make any change to
existing equipment.

Colin Bignell

On Sunday, 7 July 2013 17:22:17 UTC+2, Nightjar wrote:
On 07/07/2013 15:30, Harry Bloomfield wrote:

...

The basic numbers in the UK are 415v 3Ph. 240v single phase = 240v from

any of the three phases, to neutral. 415v as measured from any phase aay

of the other two....



Since 2003, it has been 400v and 230v, but with wider tolerances, so

that neither we nor any other EU country had to make any change to

existing equipment.



Colin Bignell

I don't really understand why we don't go for 3 phase at say 800V. Let's face it: even 230V is well into the lethal zone so going higher isn't going to be any more dangerous. Plus 800 is still low enough not to arc or flashover - given remotely adequate insulation. And just think of the saving in terms of conductor! Given the price of copper (notwithstanding it's slipped back lately) I'd have thought pushing up the supply voltages would be obvious thing to do from the pov of conserving natural resources.

wrote:
I don't really understand why we don't go for 3 phase at say 800V. Let's face it: even 230V is well into the lethal zone so going higher isn't going to be any more dangerous. Plus 800 is still low enough not to arc or flashover - given remotely adequate insulation. And just think of the saving in terms of conductor! Given the price of copper (notwithstanding it's slipped back lately) I'd have thought pushing up the supply voltages would be obvious thing to do from the pov of conserving natural resources.

One problem is the huge installed base of equipment, including cable
that is rated at the current voltages. Current insulation standards
sometimes stuggle with the current voltages, shown by exploding cables
as frequently reported in this newsgroup.

Another reason is that along every street in the country is a set of
three cables carrying the current voltages of 230V to earth, and 400V
(+-) between them. To have 800V available, the powers that be would need
to run new cables from new substations to only those users wanting 800V.

Another way to save money on the grid would be to increase the
frequency, allowing the use of smaller transformers for the same power.
The same objections apply, although aerospace applications often use
400Hz AC for this reason.

--
Tciao for Now!

John.

wrote:
I mean they're clearly two different disciples entirely. In my typically millivolt/milliamp world, we don't have to contend with forces sufficient to rip a machine's internals to pieces as you do with power engineering, so the need for nice, smooth 3 phase supplies simply doesn't arise in the first place!

I've found that most sparks I talk to don't have an in depth
understanding of the subject. They are taught largely by rote both in
college and as apprentices. They know all the how but very little why.

There are exceptions naturally.

My background like yours is in electronics but I've learned to adapt
over the years.

Bob

If you pay them, I should imagine, but if its industrial, then you might
have the gods of the council down for some business rates.
Brian

--
From the Bed of Brian Gaff.
The email is valid as
Blind user.
wrote in message
...
Hi gang,

AIUI, out in the road there are three live wires and one neutral. The phases
of the lives are 120 degrees out of phase with one another. The potential
difference between any two live wires is 440V. The potential difference
between any live and neutral is 230V. Domestic supplies only tap one live
and the neutral to give you a single phase supply, so if you want a 3 phase
supply for a workshop or whatever, you have to get the leccy blokes in to
dig up the road and tap you into one of the other live wires. Do I have that
right?

cheers.

"John Williamson" wrote in message
...
wrote:
I don't really understand why we don't go for 3 phase at say 800V. Let's
face it: even 230V is well into the lethal zone so going higher isn't
going to be any more dangerous. Plus 800 is still low enough not to arc
or flashover - given remotely adequate insulation. And just think of the
saving in terms of conductor! Given the price of copper (notwithstanding
it's slipped back lately) I'd have thought pushing up the supply voltages
would be obvious thing to do from the pov of conserving natural
resources.

One problem is the huge installed base of equipment, including cable that
is rated at the current voltages. Current insulation standards sometimes
stuggle with the current voltages, shown by exploding cables as frequently
reported in this newsgroup.

Another reason is that along every street in the country is a set of three
cables carrying the current voltages of 230V to earth, and 400V (+-)
between them. To have 800V available, the powers that be would need to run
new cables from new substations to only those users wanting 800V.

Another way to save money on the grid would be to increase the frequency,
allowing the use of smaller transformers for the same power. The same
objections apply, although aerospace applications often use 400Hz AC for
this reason.

--
Tciao for Now!

John.

Trouble is even though substation efficiency would increase, your main
transmission line losses will increase dramatically due to skin effect. It
is still significant even at 50Hz.

Andy

In article ,
writes:
I don't really understand why we don't go for 3 phase at say 800V. Let's face it: even 230V is well into the lethal zone so going higher isn't going to be any more dangerous. Plus 800 is still low enough not to arc or flashover - given remotely adequate insulation. And just think of the saving in terms of conductor! Given the price of copper (notwithstanding it's slipped back lately) I'd have thought pushing up the supply voltages would be obvious thing to do from the pov of conserving natural resources.

When you plot all the costs against each other (e.g. conductor costs,
insulator costs, switchgear costs, etc) with a very broad brush, you
tend to find the optimum is around 1000V per mile over which you are
transporting the electricity. So 240V is good for up to 1/4 mile runs
(i.e. distance from substation), and 415V (same thing strung as 3-phase)
can go a bit further with a roughly balanced load.

So between villages, you might want various mixtures of, say, 1000V to
5000V, but then the next factor comes into play - the cost of conversion,
and you don't want to do that too many times. Also, standardisation -
let's stick to some specific voltages so we don't need loads of different
transformer models, cable insulations, etc. We use 11,000 V as the
voltage between most substations, and the next one up is 33,000V, these
being good for transporting power around 11 and 33 miles respectively.
The actual power carried also has to be factored in, and you might well
get a shorter 33kV run where large amounts of power are required, or
generated to be transported to the grid.

132kV, 275kV, and 400kV are used for transporting power over longer
distances across the country, particularly as generation increasingly
moved further away from consumption. (There may still be the odd 66kV
line, but most of these were phased out as the National Grid was
constructed.)

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

Andy Bartlett wrote:
"John Williamson" wrote in message
Another way to save money on the grid would be to increase the frequency,
allowing the use of smaller transformers for the same power. The same
objections apply, although aerospace applications often use 400Hz AC for
this reason.

Trouble is even though substation efficiency would increase, your main
transmission line losses will increase dramatically due to skin effect. It
is still significant even at 50Hz.

Conflicting requirements. DC is best for long distance transmission, and
HF AC for smaller transformers...... It's Edison vs. Westinghouse all
over again. Grin

Could this be the reason why we use 50 - 60 Hz worldwide, as the best
compromise for a national grid?

--
Tciao for Now!

John.

On Sunday, 7 July 2013 19:07:50 UTC+2, Andrew Gabriel wrote:
In article ,

writes:

I don't really understand why we don't go for 3 phase at say 800V. Let's face it: even 230V is well into the lethal zone so going higher isn't going to be any more dangerous. Plus 800 is still low enough not to arc or flashover - given remotely adequate insulation. And just think of the saving in terms of conductor! Given the price of copper (notwithstanding it's slipped back lately) I'd have thought pushing up the supply voltages would be obvious thing to do from the pov of conserving natural resources.



When you plot all the costs against each other (e.g. conductor costs,

insulator costs, switchgear costs, etc) with a very broad brush, you

tend to find the optimum is around 1000V per mile over which you are

transporting the electricity. So 240V is good for up to 1/4 mile runs

(i.e. distance from substation), and 415V (same thing strung as 3-phase)

can go a bit further with a roughly balanced load.



So between villages, you might want various mixtures of, say, 1000V to

5000V, but then the next factor comes into play - the cost of conversion,

and you don't want to do that too many times. Also, standardisation -

let's stick to some specific voltages so we don't need loads of different

transformer models, cable insulations, etc. We use 11,000 V as the

voltage between most substations, and the next one up is 33,000V, these

being good for transporting power around 11 and 33 miles respectively.

The actual power carried also has to be factored in, and you might well

get a shorter 33kV run where large amounts of power are required, or

generated to be transported to the grid.



132kV, 275kV, and 400kV are used for transporting power over longer

distances across the country, particularly as generation increasingly

moved further away from consumption. (There may still be the odd 66kV

line, but most of these were phased out as the National Grid was

constructed.)



--

Andrew Gabriel

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

You see a lot of 3 wire transmission lines across the countryside. The lines are spaced about a meter apart and are supported by relatively close-to-the-ground wooden poles which aren't dissimilar to telegraph poles in appearance. You could reach them with a fishing rod they're that low in some places. I saw some hapless tree surgeon lop off a branch once that landed across two of these wires. Two little fires ignited at the contact points. Didn't look anything special at first. I expected an upstream breaker somewhere to activate and shut off the current, but that didn't happen. The fires grew rapidly and within one minute at the most there was the most *enormous* flash and ***BANG*** and everything then fell earily silent. It was one of the most spectacular things I've ever witnessed. Turned out the power to a couple of hundred thousand homes had been lost as a result. Would this have been one of your 33,000V lines? The homes affected were as far away as 35 miles from the incident, btw.

wrote in message
...


You see a lot of 3 wire transmission lines across the countryside. The
lines are spaced about a meter apart and are supported by relatively
close-to-the-ground wooden poles which aren't dissimilar to telegraph poles
in appearance. You could reach them with a fishing rod they're that low in
some places. I saw some hapless tree surgeon lop off a branch once that
landed across two of these wires. Two little fires ignited at the contact
points. Didn't look anything special at first. I expected an upstream
breaker somewhere to activate and shut off the current, but that didn't
happen. The fires grew rapidly and within one minute at the most there was
the most *enormous* flash and ***BANG*** and everything then fell earily
silent. It was one of the most spectacular things I've ever witnessed.
Turned out the power to a couple of hundred thousand homes had been lost as
a result. Would this have been one of your 33,000V lines? The homes
affected were as far away as 35 miles from the incident, btw.

Almost certainly 11kV on lines as you describe

AWEM

On 07/07/2013 18:19, John Williamson wrote:
Andy Bartlett wrote:
"John Williamson" wrote in message
Another way to save money on the grid would be to increase the
frequency, allowing the use of smaller transformers for the same
power. The same objections apply, although aerospace applications
often use 400Hz AC for this reason.

Trouble is even though substation efficiency would increase, your main
transmission line losses will increase dramatically due to skin
effect. It is still significant even at 50Hz.

Conflicting requirements. DC is best for long distance transmission, and
HF AC for smaller transformers...... It's Edison vs. Westinghouse all
over again. Grin

Or, in Britain, Crompton, Kelvin and Hopkinson v Ferranti, Mordley and
Thompson.

Could this be the reason why we use 50 - 60 Hz worldwide, as the best
compromise for a national grid?

Possibly something to do with 40Hz being about the minimum frequency at
which flicker was not noticeable to most people with early incandescent
lamps. There being a limited number of manufacturers in the world making
generating equipment was probably also a factor.

In Britain, in 1930, there were 15 different AC frequencies in use, from
25Hz to 100Hz, but 81% of all generation was at 50Hz. Standardisation
cost £17.5 million.

Colin Bignell

On 07/07/2013 19:29, Nightjar wrote:
Standardisation cost £17.5 million.

Interesting to consider the cost of not standardising would have been.

--
Rod

On Sunday, 7 July 2013 18:58:22 UTC+2, Bob Minchin wrote:
wrote:

I mean they're clearly two different disciples entirely. In my typically millivolt/milliamp world, we don't have to contend with forces sufficient to rip a machine's internals to pieces as you do with power engineering, so the need for nice, smooth 3 phase supplies simply doesn't arise in the first place!



I've found that most sparks I talk to don't have an in depth

understanding of the subject. They are taught largely by rote both in

college and as apprentices. They know all the how but very little why.



There are exceptions naturally.



My background like yours is in electronics but I've learned to adapt

over the years.



Bob

I think you may be right. A recently qualified young electrician told me, in regards to electrical safety, that "even just a few megaohms can kill you.." I shuddered at the time, but feel much less alarmed now in the light of your remarks.

On 07/07/2013 19:15, Andrew Mawson wrote:
wrote in message
...


You see a lot of 3 wire transmission lines across the countryside. The
lines are spaced about a meter apart and are supported by relatively
close-to-the-ground wooden poles which aren't dissimilar to telegraph
poles in appearance. You could reach them with a fishing rod they're
that low in some places. I saw some hapless tree surgeon lop off a
branch once that landed across two of these wires. Two little fires
ignited at the contact points. Didn't look anything special at first.
I expected an upstream breaker somewhere to activate and shut off the
current, but that didn't happen. The fires grew rapidly and within one
minute at the most there was the most *enormous* flash and ***BANG***
and everything then fell earily silent. It was one of the most
spectacular things I've ever witnessed. Turned out the power to a
couple of hundred thousand homes had been lost as a result. Would this
have been one of your 33,000V lines? The homes affected were as far
away as 35 miles from the incident, btw.

Almost certainly 11kV on lines as you describe

AWEM

Agreed, and certainly not serving 200,000 homes unless it caused a trip
in one of the much higher voltage lines, which I would have thought was
unlikely.

It went quiet because a breaker did operate, but only once there was
enough ionisation from the fire to allow an arc between phases or from
phase to ground. Perhaps a few hundred amps? Which is a few megawatts,
maybe 1000 homes?

On 07/07/2013 18:19, John Williamson wrote:
Andy Bartlett wrote:
"John Williamson" wrote in message
Another way to save money on the grid would be to increase the
frequency, allowing the use of smaller transformers for the same
power. The same objections apply, although aerospace applications
often use 400Hz AC for this reason.

Trouble is even though substation efficiency would increase, your main
transmission line losses will increase dramatically due to skin
effect. It is still significant even at 50Hz.

Conflicting requirements. DC is best for long distance transmission, and
HF AC for smaller transformers...... It's Edison vs. Westinghouse all
over again. Grin

Could this be the reason why we use 50 - 60 Hz worldwide, as the best
compromise for a national grid?

Apart from skin effect, 50-60 Hz keeps the generators simple: two poles
per phase at 3000 rpm or occasionally 4 poles at 1500 for 50 Hz. You
can't speed up big (500-650 MW) the generators significantly because you
are close to the strength limits of suitable steel. You have conversion
losses if you try to increase the frequencies with electronics. The
losses in DC converters at each end of a DC link (like the
interconnectors under the English Channel are offset by reductions in
transmission loss.

On Sunday 07 July 2013 19:15 Andrew Mawson wrote in uk.d-i-y:

wrote in message
...


You see a lot of 3 wire transmission lines across the countryside. The
lines are spaced about a meter apart and are supported by relatively
close-to-the-ground wooden poles which aren't dissimilar to telegraph
poles in appearance. You could reach them with a fishing rod they're that
low in some places. I saw some hapless tree surgeon lop off a branch once
that landed across two of these wires. Two little fires ignited at the
contact points. Didn't look anything special at first. I expected an
upstream breaker somewhere to activate and shut off the current, but that
didn't happen. The fires grew rapidly and within one minute at the most
there was the most *enormous* flash and ***BANG*** and everything then
fell earily silent. It was one of the most spectacular things I've ever
witnessed. Turned out the power to a couple of hundred thousand homes had
been lost as a result. Would this have been one of your 33,000V lines? The
homes affected were as far away as 35 miles from the incident, btw.

Almost certainly 11kV on lines as you describe

AWEM

Dunno - the Robertsbridge overhead feeders are 33kV (it says so on some of
the warning labels) and they are wooden poles, lines fairly close, low down.
--
Tim Watts Personal Blog: http://squiddy.blog.dionic.net/

http://www.sensorly.com/ Crowd mapping of 2G/3G/4G mobile signal coverage

Reading this on the web? See:
http://wiki.diyfaq.org.uk/index.php?title=Usenet

"John Williamson" wrote in message
...
wrote:
I don't really understand why we don't go for 3 phase at say 800V. Let's
face it: even 230V is well into the lethal zone so going higher isn't
going to be any more dangerous. Plus 800 is still low enough not to arc
or flashover - given remotely adequate insulation. And just think of the
saving in terms of conductor! Given the price of copper (notwithstanding
it's slipped back lately) I'd have thought pushing up the supply voltages
would be obvious thing to do from the pov of conserving natural
resources.

One problem is the huge installed base of equipment, including cable that
is rated at the current voltages. Current insulation standards sometimes
stuggle with the current voltages, shown by exploding cables as frequently
reported in this newsgroup.

Another reason is that along every street in the country is a set of three
cables carrying the current voltages of 230V to earth, and 400V (+-)
between them. To have 800V available, the powers that be would need to run
new cables from new substations to only those users wanting 800V.

Another way to save money on the grid would be to increase the frequency,
allowing the use of smaller transformers for the same power. The same
objections apply, although aerospace applications often use 400Hz AC for
this reason.

In days of yore as the national grid was being created, the were auto
trnasformers between areas of different local voltages as a temporary thing.
The electricity boards were responsible for collecting up all appliances and
converting to the new voltage. Vast job even back then. Pre and post war.

There would be no save for higher frequency in fact there would be increased
iron or magnetic losses.
Power is realated to voltage and in-phase component of the current only.

The reason aircraft run on high frequency is that electric
motors/transformers can be made much smaller and lighter because more power
can be transmitted through any magnetic circuit by increasing the frequency.
However they are far less efficient.
Cable sizes are unaffected.

50 Hz is not the optimum frequency either.
The Yanks have it right, 60Hz is optimum.

If anything, we may go to DC in the future. Makes a lot more sense these
days.
I remeber helping to remove DC stuff back in the 60's.
And put some in.
It was the induction motor that did it.
Mostly it was in places that got their initial electricity from coal
mine/factory power houses.
We will have come full circle.

On Sunday, 7 July 2013 18:07:50 UTC+1, Andrew Gabriel wrote:
In article ,

writes:

I don't really understand why we don't go for 3 phase at say 800V. Let's face it: even 230V is well into the lethal zone so going higher isn't going to be any more dangerous. Plus 800 is still low enough not to arc or flashover - given remotely adequate insulation. And just think of the saving in terms of conductor! Given the price of copper (notwithstanding it's slipped back lately) I'd have thought pushing up the supply voltages would be obvious thing to do from the pov of conserving natural resources.



690V (400V to neutral) three-phase is used in some countries, suitably-wound motors can be used at 400V delta or 690V star, so easing standardisation, maybe we should consider it.


132kV, 275kV, and 400kV are used for transporting power over longer

distances across the country, particularly as generation increasingly

moved further away from consumption. (There may still be the odd 66kV

line, but most of these were phased out as the National Grid was

constructed.)



--

Andrew Gabriel

Actually there's still quite a bit of 66kV, it's been established in North-East England from the time of the 'Newcastle-on-Tyne Electric Supply Co' who built a regional grid between the wars, also for underground cables in London where 33kV isn't enough and 132kV cables would be too expensive.

It went quiet because a breaker did operate, but only once there was

enough ionisation from the fire to allow an arc between phases or from

phase to ground. Perhaps a few hundred amps? Which is a few megawatts,

maybe 1000 homes?

Nope. Definitely a couple of hundred thousand. I should, however, point out that this was back in the late 70s, so it's possible they've reduced the voltages these lines are permitted to carry since then.

On Sunday, 7 July 2013 21:25:16 UTC+2, Tim Watts wrote:
On Sunday 07 July 2013 19:15 Andrew Mawson wrote in uk.d-i-y:



wrote in message

...





You see a lot of 3 wire transmission lines across the countryside. The

lines are spaced about a meter apart and are supported by relatively

close-to-the-ground wooden poles which aren't dissimilar to telegraph

poles in appearance. You could reach them with a fishing rod they're that

low in some places. I saw some hapless tree surgeon lop off a branch once

that landed across two of these wires. Two little fires ignited at the

contact points. Didn't look anything special at first. I expected an

upstream breaker somewhere to activate and shut off the current, but that

didn't happen. The fires grew rapidly and within one minute at the most

there was the most *enormous* flash and ***BANG*** and everything then

fell earily silent. It was one of the most spectacular things I've ever

witnessed. Turned out the power to a couple of hundred thousand homes had

been lost as a result. Would this have been one of your 33,000V lines? The

homes affected were as far away as 35 miles from the incident, btw.



Almost certainly 11kV on lines as you describe



AWEM



Dunno - the Robertsbridge overhead feeders are 33kV (it says so on some of

the warning labels) and they are wooden poles, lines fairly close, low down.

--

Tim Watts Personal Blog: http://squiddy.blog.dionic.net/



http://www.sensorly.com/ Crowd mapping of 2G/3G/4G mobile signal coverage



Reading this on the web? See:

http://wiki.diyfaq.org.uk/index.php?title=Usenet

Wow! That's precisely the line I was talking about!!!

In article , harryagain
wrote:

"John Williamson" wrote in message
...
wrote:
I don't really understand why we don't go for 3 phase at say 800V.
Let's face it: even 230V is well into the lethal zone so going higher
isn't going to be any more dangerous. Plus 800 is still low enough
not to arc or flashover - given remotely adequate insulation. And
just think of the saving in terms of conductor! Given the price of
copper (notwithstanding it's slipped back lately) I'd have thought
pushing up the supply voltages would be obvious thing to do from the
pov of conserving natural resources.

One problem is the huge installed base of equipment, including cable
that is rated at the current voltages. Current insulation standards
sometimes stuggle with the current voltages, shown by exploding cables
as frequently reported in this newsgroup.

Another reason is that along every street in the country is a set of
three cables carrying the current voltages of 230V to earth, and 400V
(+-) between them. To have 800V available, the powers that be would
need to run new cables from new substations to only those users
wanting 800V.

Another way to save money on the grid would be to increase the
frequency, allowing the use of smaller transformers for the same
power. The same objections apply, although aerospace applications
often use 400Hz AC for this reason.

In days of yore as the national grid was being created, the were auto
trnasformers between areas of different local voltages as a temporary
thing. The electricity boards were responsible for collecting up all
appliances and converting to the new voltage. Vast job even back then.
Pre and post war.


certainly up to 1962, Cambridge town was supplied wth 200v mains. Sellers
of electrical goods needed to supply the right ones for use there. My 200v
coffee pot survived about 1 year on 240v elsewhere, my soldering iron -
quite a bit longer.

--
From KT24

Using a RISC OS computer running v5.18

On 07/07/2013 15:32, wrote:
I mean they're clearly two different disciples entirely. In my
typically millivolt/milliamp world, we don't have to contend with
forces sufficient to rip a machine's internals to pieces as you do
with power engineering, so the need for nice, smooth 3 phase supplies
simply doesn't arise in the first place!

I found doing a bit of software development work on high power HF
amplifiers / transmitters was quite enlightening in that respect... It
certainly changes ones TTL/5V view of the world, when dealing with 10kV
step up transformers!



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

certainly up to 1962, Cambridge town was supplied wth 200v mains. Sellers
of electrical goods needed to supply the right ones for use there. My 200v
coffee pot survived about 1 year on 240v elsewhere, my soldering iron -
quite a bit longer.


Did we ever settle that Ac or DC argument Can't remember now;!)...

--
Tony Sayer

On 07/07/2013 14:43, The Other Mike wrote:
On Sun, 7 Jul 2013 05:59:03 -0700 (PDT),
wrote:

Hi gang,

AIUI, out in the road there are three live wires and one neutral. The phases of the lives are 120 degrees out of phase with one another. The potential difference between any two live wires is 440V. The potential difference between any live and neutral is 230V. Domestic supplies only tap one live and the neutral to give you a single phase supply, so if you want a 3 phase supply for a workshop or whatever, you have to get the leccy blokes in to dig up the road and tap you into one of the other live wires. Do I have that right?

No good tapping into just one of the other live wires you need two
more.

Five wires in total

L1
L2
L3
N
E

Plus a new three phase meter (or another two single phase ones)

and a big hole in your bank account

Not entirely sure, but when they replaced the main fuse and housing here
some years ago, I'm sure I remember seeing four cores (three phases +
neutral, with the sheath as earth). It could well be that they brought
3-phase to every house on the road when they were built in the 30s and
only connected one phase at each. If I were to need 3-phase, that'd be a
useful cost saving!

SteveW

In article , SteveW
wrote:
On 07/07/2013 14:43, The Other Mike wrote:
On Sun, 7 Jul 2013 05:59:03 -0700 (PDT), wrote:

Hi gang,

AIUI, out in the road there are three live wires and one neutral. The
phases of the lives are 120 degrees out of phase with one another. The
potential difference between any two live wires is 440V. The potential
difference between any live and neutral is 230V. Domestic supplies
only tap one live and the neutral to give you a single phase supply,
so if you want a 3 phase supply for a workshop or whatever, you have
to get the leccy blokes in to dig up the road and tap you into one of
the other live wires. Do I have that right?

No good tapping into just one of the other live wires you need two more.

Five wires in total

L1 L2 L3 N E

Plus a new three phase meter (or another two single phase ones)

and a big hole in your bank account

Not entirely sure, but when they replaced the main fuse and housing here
some years ago, I'm sure I remember seeing four cores (three phases +
neutral, with the sheath as earth). It could well be that they brought
3-phase to every house on the road when they were built in the 30s and
only connected one phase at each. If I were to need 3-phase, that'd be a
useful cost saving!

This house (built 1911) has all 3 phases incoming - I assume so proper
balance could be obtained empirically. When they built a new estate of 25
bungalows, just round the corner, some 30 years ago - they were all on the
same phase. How things change.

--
From KT24

Using a RISC OS computer running v5.18

On Sun, 7 Jul 2013 10:56:36 -0700 (PDT),
wrote:

You see a lot of 3 wire transmission lines across the countryside. The
lines are spaced about a meter apart and are supported by relatively
close-to-the-ground wooden poles which aren't dissimilar to telegraph
poles in appearance.

Most of those are the 11 kV local distribution. Some maybe 33 kV
feeds to local area substations. Look at the insulators, around here
the 11 Kv ones are small, brown with one flange. The 33 kV ones are
larger glass and have two flanges.

The fires grew rapidly and within one minute at the most there was the
most *enormous* flash and ***BANG*** and everything then fell earily
silent. It was one of the most spectacular things I've ever witnessed.

Yes there is *a lot* of energy available on an 11 kV line. Wouldn't
be surprised if the potential short circuit current is measured in
the low kA, so with 11 kV driving it you have 10's of megawatts
available. Put it all in a small space and you get a very big bang...

Plenty of videos of substation fires, arc overs etc on YouTube.

--
Cheers
Dave.

On Sunday, July 7, 2013 9:17:11 PM UTC+1, charles wrote:
certainly up to 1962, Cambridge town was supplied wth 200v mains.

There's still a bit of kit up at the Institute of Astronomy which
runs at 200V. Apparently the electricity board threw up their hands
in horror at the complexity of replacing it, and just fitted a
suitable transformer.

On 08/07/2013 06:14, charles wrote:
In article , SteveW
wrote:
....
Not entirely sure, but when they replaced the main fuse and housing here
some years ago, I'm sure I remember seeing four cores (three phases +
neutral, with the sheath as earth). It could well be that they brought
3-phase to every house on the road when they were built in the 30s and
only connected one phase at each. If I were to need 3-phase, that'd be a
useful cost saving!

This house (built 1911) has all 3 phases incoming - I assume so proper
balance could be obtained empirically.

It was once normal practice to connect each house in turn to a different
phase. As you say, that was to achieve phase balance.

When they built a new estate of 25
bungalows, just round the corner, some 30 years ago - they were all on the
same phase. How things change.

That stops people importing 400v into their house by putting an
extension lead over the fence, or otherwise sharing supplies.

Colin Bignell

On 08/07/2013 15:12, Nightjar wrote:
On 08/07/2013 06:14, charles wrote:
In article , SteveW

wrote:
...
Not entirely sure, but when they replaced the main fuse and housing here
some years ago, I'm sure I remember seeing four cores (three phases +
neutral, with the sheath as earth). It could well be that they brought
3-phase to every house on the road when they were built in the 30s and
only connected one phase at each. If I were to need 3-phase, that'd be a
useful cost saving!

This house (built 1911) has all 3 phases incoming - I assume so proper
balance could be obtained empirically.

It was once normal practice to connect each house in turn to a different
phase. As you say, that was to achieve phase balance.

When they built a new estate of 25
bungalows, just round the corner, some 30 years ago - they were all on
the
same phase. How things change.

That stops people importing 400v into their house by putting an
extension lead over the fence, or otherwise sharing supplies.

Which if your road is wired like that, would be a pretty cheap way of
getting three phase if you get on with both neighbours ;-)



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 08/07/2013 15:24, John Rumm wrote:
On 08/07/2013 15:12, Nightjar wrote:
On 08/07/2013 06:14, charles wrote:
In article , SteveW

wrote:
...
Not entirely sure, but when they replaced the main fuse and housing
here
some years ago, I'm sure I remember seeing four cores (three phases +
neutral, with the sheath as earth). It could well be that they brought
3-phase to every house on the road when they were built in the 30s and
only connected one phase at each. If I were to need 3-phase, that'd
be a
useful cost saving!

This house (built 1911) has all 3 phases incoming - I assume so proper
balance could be obtained empirically.

It was once normal practice to connect each house in turn to a different
phase. As you say, that was to achieve phase balance.

When they built a new estate of 25
bungalows, just round the corner, some 30 years ago - they were all on
the
same phase. How things change.

That stops people importing 400v into their house by putting an
extension lead over the fence, or otherwise sharing supplies.

Which if your road is wired like that, would be a pretty cheap way of
getting three phase if you get on with both neighbours ;-)

When I worked for an electricity board, it was more usually done
surreptitiously, in one case by cutting small holes through the wall and
driving six inch nails through the neighbour's meter tails, in order to
keep the electricity bill down.

Colin Bignell