230V/240V Question

[ban-all-sheds]

Maybe the basic thing you are all missing is that some countries were on a nominal 220V ±x and some were on a nominal 240V ±x.

 

[PBC_1966]

And some places were already nominally 230V. I don't think anybody has missed that.

 

[JohnW2]

Maybe the basic thing you are all missing is that some countries were on a nominal 220V ±x and some were on a nominal 240V ±x.

I don't think anyone has missed that, but it doesn't make the situation any more understandable. My understanding is that the former of the countries you mention are, during the 'transition period', required to have a supply of 230V -10%/+6%, and the latter countries a supply of 230V -6%/+10%. Since 230V -10%/+6% and 230V -6%/+10% are both subsets of 230V ±10% (which is apparently their initial ultimate 'aim'), why on earth do all countries not now describe their supplies as 230V ±10% ?? That would be 'harmonisation', at least in one sense.

Kind Regards, John

 

[DetlefSchmitz]

Surely the point is that there could theoretically be a product/appliance/whatever within one of the countries, made to comply with the voltage range in that country, which might theoretically be damaged or non-operational if the country's supply range was increased in practice, so it would not be fair to suddenly increase the stated range until such products were deemed to have had time to change or disappear.

 

[JohnW2]

Surely the point is that there could theoretically be a product/appliance/whatever within one of the countries, made to comply with the voltage range in that country, which might theoretically be damaged or non-operational if the country's supply range was increased in practice, so it would not be fair to suddenly increase the stated range until such products were deemed to have had time to change or disappear.

Yes, but you seem to be overlooking the fact that we are only talking about an on-paper exercise. AFAIAA, in no countries have the appliances or the supply voltage changed as a result of these 'pronouncements', so those appliances should still work, and work as safely, as they ever have done. If, for some reason, there is a desire to be able to say that all countries have a supply within the range 230V±10%, then why not simply say so now - since it's true.

I can but presume that the ultimate plan/desire (probably over very many decades) is for the actual average supply voltages to all get closer to 230V and, probably ultimately, for the permitted ±10% to be tightened.

Kind Regards, John

 

[DetlefSchmitz]

I don't think I'm missing that. If this country changed the statement of permissible voltage from 230V -6%/+10% to 230V ±10% (on paper if you like) then we would officially have to accept a supply which was lower than before. The voltages reaching different user could get lower if some places because it was expedient to do so for the supplier, and the paper change would give them the go ahead.

 

[JohnW2]

I don't think I'm missing that. If this country changed the statement of permissible voltage from 230V -6%/+10% to 230V ±10% (on paper if you like) then we would officially have to accept a supply which was lower than before. The voltages reaching different user could get lower if some places because it was expedient to do so for the supplier, and the paper change would give them the go ahead.

Yes, that is theoretically possible, although I doubt that they would want to have to deal with all the hassle from consumers, despite the "on-paper go-ahead" - as I said, AFAIAA suppliers are not changing their supply as a result of the 'harmonisation'. Whatever, as I wrote recently, if the change to ±10% has to be delayed until it is felt that all equipment/appliances which doesn't function satisfactorily at supply voltages <216.2V has been retired, then I doubt that any of us will be around to see the change to ±10%!

We've already been through this once without any obvious fuss or problems. On 1st Jan 1995, the minimum permitted UK supply voltage fell from 225.6V (240V -6%) to 216.2V (230V -6%), a fall of 9.4V. If that was 'painless', then maybe a further, similar, fall of 9.2V (to 207.0V - aka 230V -10%), after a 21-year period of 'adjustment', would not be very painful either? I may be wrong, but I'm not aware of any evidence that suppliers significantly 'took advantage' of the 9.4V reduction in supply voltage they could theoretically have implemented in 1995, so I rather doubt they would do so 'next time'.

Kind Regards, John

 

[PBC_1966]

I don't think I'm missing that. If this country changed the statement of permissible voltage from 230V -6%/+10% to 230V ±10% (on paper if you like) then we would officially have to accept a supply which was lower than before. The voltages reaching different user could get lower if some places because it was expedient to do so for the supplier, and the paper change would give them the go ahead.

As John has already mentioned, the change (on paper) from a lower limit of 240V -6% to 230V -6% has already given sanction to the suppliers to start allowing the delivered voltage to be considerably lower during high-demand periods if it's expedient (i.e. convenient and cheaper) for them to do so. As far as the U.K. is concerned, do you really want to see an eventual widening of the supply tolerance to a symmetrical 10% either side of 230V? If suppliers really are going to start changing transformers over the years, then it would be much better if the aim were to wait until everywhere has been changed (which could be many decades), then tighten the specification to 230V +/-6%.

Of course, that wouldn't satisfy those who seem to think that merely for the sake of "harmoniuzation" if Europe is operating to 230V +/-10% then the U.K. should too, even though 230V +/-6% falls entirely within that wider range and even though the 6% tolerance would maintain the U.K.'s better regulation.

 

[JohnW2]

As far as the U.K. is concerned, do you really want to see an eventual widening of the supply tolerance to a symmetrical 10% either side of 230V? If suppliers really are going to start changing transformers over the years, then it would be much better if the aim were to wait until everywhere has been changed (which could be many decades), then tighten the specification to 230V +/-6%.

As far as I can make out, that is, indeed the (very) long-term plan/desire/intent - and throughout Europe, not just in UK.

The narrowing of tolerance limits (which is probably going to happen eventually) will, of course, have some major potential implications in terms of the LV networks, since many of the existing ones probably could not maintain supply voltage within much tighter limits (at both minimum and maximum demand on the local network) for consumers at the end of a long cable run. Whereas gradually changing to an average supply closer to 230V can be done (very slowly!) at minimum effort or cost if it is done by only changing things when transformers need replacing, dealing with tighter voltage limits could involve a lot of costly digging and re-cabling.

Kind Regards, John

 

[PBC_1966]

Certainly, if that's the eventual aim (230V +/-6%) then I would hope the suppliers would, in places where transformers have not been changed, keep to the existing tolerances of 240V +/-6% rather than try to get away with adding more and more load without updating things, taking advantage of that extra 9V drop or so now permitted, then they won't have to engage in yet more costly recabling or reorganization of the network when they do get around to changing he supply transformer to 230V.

I think it may well be a much more costly process to achieve that eventual +/-6% in some other countries, which have in the past traditionally accepted much wider variations in supply voltage.

 

[stillp]

There seems to be a move by the generation and distribution companies to widen the effective tolerances further, to accommodate the increasing use of "renewable" sources, which are leading to instability in some areas.

 

[stillp]

OK, now I have the latest version on EN 50160, here are the criteria for supply voltage variation:
Under normal operating conditions:
− during each period of one week 95 % of the 10 min mean r.m.s. values of the supply voltage shall
be within the range of Un ± 10 %; and
− all 10 min mean r.m.s. values of the supply voltage shall be within the range of Un + 10 % / - 15 %.

Some might also be interested in the following definition:
3.16
nominal voltage
Un
voltage by which a supply network is designated or identified and to which certain operating
characteristics are referred

 

[JohnW2]

"− during each period of one week 95 % of the 10 min mean r.m.s. values of the supply voltage shall be within the range of Un ± 10 %; and
− all 10 min mean r.m.s. values of the supply voltage shall be within the range of Un + 10 % / - 15 %...."

Thanks. The first bit of that is what we've already been told (e.g. by westie) - although the ± 10 % presumably does not apply to countries like the UK which, during this never-ending transition period, are working to asymmetrical limits?

The second bit really means that only part of the first is relevant. If 100% of 10-min means are required to be below Un + 10%, then it is apparent than 'no percent' of them could be over Un + 10% - so the first bit is only really relevant in terms of negative excursions.

Some might also be interested in the following definition: " 3.16 ... nominal voltage ... Un
voltage by which a supply network is designated or identified and to which certain operating characteristics are referred

As you say, 'interesting' - but it could mean almost anything! However, as I've been saying, it does sound as if they are using the word 'nominal' is a sense different from its usual meaning in most engineering (and many other) situations. It does seem a bit silly to have such a vague definition, since the whole concept (particularly citing tolerances relative to this 'nominal value') becomes nonsensical if the value of this 'nominal' voltage is not at least somewhere near the 'intended' voltage! Percentages above and below an 'arbitrary number' do seem to be a rather odd concept!

Kind Regards, John

 

[stillp]

'interesting' - but it could mean almost anything!

Which of the words are you having difficulty understanding John?

 

[JohnW2]

'interesting' - but it could mean almost anything!

Which of the words are you having difficulty understanding John?

I understand the words but, as I said, they fall very far short of saying what (if anything) they actually mean! "...voltage by which a supply network is designated or identified.." means nothing useful. What relationship, if any, is this 'designator'/'identifier' meant to have with the actual, or desired, or whatever, voltage supplied?

I suppose what I really don't understand is all this apparent 'beating around the bush'. If there is any sense in it at all, the underlying intent is presumably that, in the fullness of a lot of time, the 'average' voltage supplied in all countries will be around 230V. If that is the case, why don't they simply say so? Indeed, by imposing limits in terms of percentages above and below that 'nominal' value, they are more or less saying that. Admittedly some of the ranges are currently asymmetrical around the 'nominal' - but that is allegedly only a temporary ('transitional') situation.

Kind Regards, John