George You are right that the UK still generates electricity to give single phase supplies centred at 240V. This is despite changing its nominal to 230V to harmonise with the EU. It is allowed a variation of +10% and -6%. of the nominal 230V (216 - 253) but unlike true 230V countries it is habitually at the top end of that range. I have frequently seen voltages at the socket of 245V to 247V As well the effect you mention of high voltage at times of low usage there is also the effect of neutral offset caused by unbalanced phase loads. UK supplies to domestic and commercial premises use a balanced three phase and neutral cable and connect premises to one of the phases and neutral. In a housing estate every third house is connected each phase.A large load on one phase will cause a voltage drop down the neutral. Neutral to earth voltages of 10 to 15 volts are not uncommon. Because this voltage is at 120° to the other phases a half its value will be added to the phase to neutral voltages of the other phases. It would not surprise me if occasionally the voltage exceeded 254V Another thing to remember about countries with a high supply voltage is that the voltage spikes are correspondingly higher as those generated on the high voltage transmission lines are transformed down by a lower ratio
Nick Rouse ----- Original Message ----- From: <[email protected]> To: <[email protected]> Cc: <[email protected]> Sent: Friday, February 02, 2001 7:30 PM Subject: Re: 230 Vac or 240 Vac? > > > David, > > Here is my understanding based on an earlier discussion on this forum > and some of our business experiences. The agreement amongst many high > volt countries was on a 220-240V range. This implies a 230V nominal. > The 240V countires agreed, but never changed their nominals, as this > would have involved serious changes to their power generation equipment. > > Their reasoning was that a product rated at 220-240V is required under > IEC 60950 and like standards to be tested up to 6% over rated voltage, > i.e. a max of 254V. They assumed they could deliver power to the end > users within this range without changing their nominals. > > I'm beginning to doubt this assumption as we have had numerous reports > of our direct plug-in external power supplies running "hot" in two > geographies only, viz. the U.K. and Australia/New Zealand. Since we > have specified and tested up to 254V without problems, it is my belief > that the end users may be seeing over 254V on low periods of the day. > High usage periods result in more IR drop along the transmission paths, > and reduce the end voltage. > > This is just my opinion based on my experiences. > > George Alspaugh > Lexmark International Inc. > > > > > gelfand%[email protected] on 02/02/2001 10:56:22 AM > > Please respond to gelfand%[email protected] > > To: emc-pstc%[email protected] > cc: (bcc: George Alspaugh/Lex/Lexmark) > Subject: 230 Vac or 240 Vac? > > > > > Group, > > I seem to remember that Australia was changing their nominal voltage from 240 to > 230 V. Is this true? Are there other countries that have nominal voltages of > 240 V? I want to determine the maximum voltage for leakage current tests. > > Best regards, > > David. > > David Gelfand > Regulatory Approvals > Memotec Communications Inc. > Montreal Canada > > > > > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Jim Bacher: [email protected] > Michael Garretson: [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected]
