Doorbell transformer

[RF Lighting]

But you don't accept that the supply figure is nominal, so how can all those different figures be right? Surely there is just one voltage which is right?

 

[bernardgreen]

Hello Winston

The UK was designed to operate on 240 volts while Europe chose 230 volts for most of the land mass. There were a few exceptions. I seem to recall a hotel in Paris that had 100 volts, so long ago I can't remember the date.

Then Europe took over the UK and told us to change to 230 volts to be in line with every one else. So we did change to 230 volts but with British ingenuity the specification was change to include 240 volts as an acceptable over voltage on a 230 volt supply. This meant the UK generating stations didn't need to alter anything. they could run at 240 volts.

Does that help you understand why a NOMINAL 230 volt network is supplying 240 volts to almost all domestic places that use electricity in the UK

 

[ajsdoc]

Doorbell works.....

 

[JohnW2]

Whenever I have measured it over the last 50 years it has been around 242v. I have never seen it below 237 or above 245V. I therefore think it is around 240V, certainly not 230V.

Very much the same here. I know that I'll come to regret 'getting involved' yet again, but if only you would stop going on about it, I think you could probably rest in the knowledge that many, perhaps most, of us actually agree with most of what you say about this issue - that it's basically daft and unhelpful to have this situation in which the bureaucratic 'nominal' supply voltage differs appreciably from the 'most common' supply voltage in the UK. I think that the only main difference between you and many of us is that we accept that we are, at least for the time being, stuck with this situation, and that absolutely nothing is to be gained by annoyingly 'going on about it'.

What I'm less convinced about is that there are 'no plans to reduce the UK supply voltage'. It would not surprise me if, very gradually, it is shifted closer to the stated 'nominal' - not the least because that would probably offer some benefits for the suppliers.

Kind Regards, John

 

[bernardgreen]

Some light reading for Winston

http://zapatopi.net/kelvin/papers/electric_lighting_and_public_safety.html

 

[JohnW2]

...So we did change to 230 volts but with British ingenuity the specification was change to include 240 volts as an acceptable over voltage on a 230 volt supply. This meant the UK generating stations didn't need to alter anything. they could run at 240 volts.

Indeed - but it doesn't really affect the generating stations - it's only at the level of the final transformer (from HV to LV) that the final supply voltage becomes relevant, and I was under the impression that there is already a significant amount of 'adjustability' (taps) available.

As I've just written, it would not surprise me if we were to see a (probably very gradual) change to something closer to 230V, particularly for domestic supplies. It is in the interests of the DNOs to have the 'usual' supply voltage fairly near to the middle of the permissible range and, given that the great majority of large domestic loads are 'dumb resistive', it's quite possible that there might be a reduction in at least some peaks of demand if voltage were reduced.

Kind Regards, John

 

[winston1]

Hello Winston

The UK was designed to operate on 240 volts while Europe chose 230 volts for most of the land mass. There were a few exceptions. I seem to recall a hotel in Paris that had 100 volts, so long ago I can't remember the date.

Then Europe took over the UK and told us to change to 230 volts to be in line with every one else. So we did change to 230 volts but with British ingenuity the specification was change to include 240 volts as an acceptable over voltage on a 230 volt supply. This meant the UK generating stations didn't need to alter anything. they could run at 240 volts.

Does that help you understand why a NOMINAL 230 volt network is supplying 240 volts to almost all domestic places that use electricity in the UK

Wrong apart from the first nine words. Much of Europe was on 127V including that hotel in Paris in the 60's. Later they changed to 220V sometimes just by using 2 phases of the existing supply.
No one told us to change. With harmonisation it was decided it would be better if everyone was the same. France considered upping to 240V but decided 10% increase was too much for existing equipment so 230V it was. Not sure if it has actually changed though. Certainly the UK has not reduced to 230V, only some idiots calling 240V a nominal 230V.

 

[RF Lighting]

The idiots as you call them are of course right, but it's nothing new for you to be wrong.

 

[winston1]

Whenever I have measured it over the last 50 years it has been around 242v. I have never seen it below 237 or above 245V. I therefore think it is around 240V, certainly not 230V.

Very much the same here. I know that I'll come to regret 'getting involved' yet again, but if only you would stop going on about it, I think you could probably rest in the knowledge that many, perhaps most, of us actually agree with most of what you say about this issue - that it's basically daft and unhelpful to have this situation in which the bureaucratic 'nominal' supply voltage differs appreciably from the 'most common' supply voltage in the UK. I think that the only main difference between you and many of us is that we accept that we are, at least for the time being, stuck with this situation, and that absolutely nothing is to be gained by annoyingly 'going on about it'.

What I'm less convinced about is that there are 'no plans to reduce the UK supply voltage'. It would not surprise me if, very gradually, it is shifted closer to the stated 'nominal' - not the least because that would probably offer some benefits for the suppliers.

Kind Regards, John

Noted, but I did not start this discussion again. It was AndyPRK with his comment.

 

[JohnW2]

Noted, but I did not start this discussion again. It was AndyPRK with his comment.

It was, but I think you'd get a lot more respect if you resisted responding to such bait and, like the rest of us, avoided repetition of things we've read so many times before (and which, as I said, many of us probably largely agree with).

Kind Regards, John

 

[DetlefSchmitz]

I don't think that Winston really understands what nominal voltage means. It is a number which the DNO can use to determine whether they are meeting their commitments.

So at one end of our road (next to the transformer) the voltage happens to be 250V, which is 230 + 8.7% and therefore within the limit.

At the other end of the road the voltage is typically 229V (230 - 0.5%), and therfore within the limit.

So the DNO are meeting their commitments defined by the nominal voltage. None of these voltage are 240V, or indeed any other voltage. They vary with time and the tap chosen on the transformer to satisfy the requirements of all the houses in the road.

If they can't do this at all times of the day (and load) then they would have to put thicker wire in the road or add another transformer at the other end of the road, or tell everyone to use less power.

Across Europe it is necessary that appliances sold to the public will work without damage, wherever they are sold. This is the reason for choosing a voltage and a tolerance which everyone in Europe can agree on. So the appliance manufacturers and the DNOs all work to the same rules which means we have a market for appliances which works beyond our UK shores. This is a good thing because it keeps prices down.

It is worth saying too, that the voltage supplied to a house has to be 4% higher than the minimum voltage permitted to allow for the voltage drop requirements of BS7671, but can never be higher than 253V. And it has to be in this range whatever the loading on the street cabling might be.

So, saying that the voltage is 'really' any particular value is just being stupid. It is an engineering compromise.

 

[winston1]

Of course those figures would also be in tolerance with 240V + or - 6% nominal. Funny that, nothing has changed as I've already said. Modern appliances work quite happily over a wide voltage range, often 100 to 250V. This was not always the case and voltage selectors were fitted for use in different areas. Even today though things like incandescent light bulbs need a much closer tolerance than +10 -6% for optimum performance and life.

 

[JohnW2]

I don't think that Winston really understands what nominal voltage means. It is a number which the DNO can use to determine whether they are meeting their commitments.

If it were only that, then there would be less to moan about. However, that 'nominal voltage' has, at least hitherto, been used for virtually all (mainly safety-related) calculations specified in, say, BS7671 (and probably other regulations) - which leads to potential concerns if it is appreciably different from the actual voltage delivered. Come tomorrow, we expect to see published the first example of BS7671 effectively deviating from this use of nominal voltage for all calculations - and it might possibly be the first of many such changes.

Given that supply voltage to any installation varies, one obviously has to have some 'fixed' figures to use for calculations. Depending upon the nature of the calculation, the conservative figure to use will usually be either the minimum or maximum permitted supply voltage, but for some purposes 'the most common average' might be appropriate - but, in engineering/mathematical terms, it is probably never really appropriate to use an essentially arbitrary, 'bureaucratically-determined' figure for such calculations.

It is worth saying too, that the voltage supplied to a house has to be 4% higher than the minimum voltage permitted to allow for the voltage drop requirements of BS7671, but can never be higher than 253V.

I'm not so sure about (the first part) of that. As often discussed, in the presence of such wide permitted supply voltage variation, most of what is said about VD is pretty daft, but I'm not sure that there is anything in BS7671 which says that 'permitted voltage drops' are not allowed if they take the voltage at the end of the circuit down to below the permitted minimum supply voltage (2.16,2V), is there? Also, as westie often reminds us, supply voltage is apparently allowed to deviate outside of the range 216.2V-253V for 5% of the time!

Kind Regards, John

 

[DetlefSchmitz]

It is worth saying too, that the voltage supplied to a house has to be 4% higher than the minimum voltage permitted to allow for the voltage drop requirements of BS7671, but can never be higher than 253V.

I'm not so sure about (the first part) of that. As often discussed, in the presence of such wide permitted supply voltage variation, most of what is said about VD is pretty daft, but I'm not sure that there is anything in BS7671 which says that 'permitted voltage drops' are not allowed if they take the voltage at the end of the circuit down to below the permitted minimum supply voltage (2.16,2V), is there? Also, as westie often reminds us, supply voltage is apparently allowed to deviate outside of the range 216.2V-253V for 5% of the time!

OK - so think of what I said as a challenge or question. An appliance manufacturer is required to ensure that their appliance works from -6% to +10%. A DNO is required to supply exactly the same voltage to the supply terminals of the house. So how do we account for the remaining 4%? Whose problem is that?

 

[JohnW2]

I'm not so sure about (the first part) of that. As often discussed, in the presence of such wide permitted supply voltage variation, most of what is said about VD is pretty daft, but I'm not sure that there is anything in BS7671 which says that 'permitted voltage drops' are not allowed if they take the voltage at the end of the circuit down to below the permitted minimum supply voltage (2.16,2V), is there? Also, as westie often reminds us, supply voltage is apparently allowed to deviate outside of the range 216.2V-253V for 5% of the time!

OK - so think of what I said as a challenge or question. An appliance manufacturer is required to ensure that their appliance works from -6% to +10%.

Who or what says that? I've seen appliances labelled/rated/'speced' "220V", "230V", "240V", "220V-240V" and various things like that, but never one labelled/rated/'speced' "230V -6% +10%" or "216.2V - 253V" - have you?

A DNO is required to supply exactly the same voltage to the supply terminals of the house. So how do we account for the remaining 4%? Whose problem is that?

I'm really not sure where your 4% comes from (I obviously realise that 10-6=4, but I'm not sure what that's got to do with anything ). I thought you were talking about the so-called 'BS7671-permitted' VD within installations (5%, or 3% if lighting) - and, as I said, I see nothing in BS7671 which says that there can't be a 5% (11.5V) VD within an installation (for a non-lighting load) even if the supply voltage is only 216.2V (such that the voltage reaching the appliance is only 204.7V), can you?

Kind Regards, John