They reduced it to 230 didn't they "officially"? And increased Europe from 220 to 230 - so we all match? In reality, they made sure the tolerances on everything was such that they could continue as before.
Adam
Background
Electrical equipment has to be designed to accept a range of input voltages about its nominal design centre, but if the actual supply is higher than necessary for proper operation, the equipment will consume more power than needed, and also in many cases life is reduced - both increasing the cost of ownership.
However, the stability of the UK supply mains has always been reasonably good, but is likely to degrade as competition and decreasing profitability forces generators to take capacity off-line and indeed to decommission power stations.
European Voltage Harmonisation
The United Kingdom for many years had a standardised supply voltage of 240V ±6% (415V for three-phase) whereas continental Europe had a nominal supply level of 220V (380V). From 1 January 1995 the nominal voltage across Europe has been 'harmonised' at 230V/400V.
This is not a real change, since the former 240V countries, including the UK, have in the first stage of voltage harmonisation a tolerance of 230V -6% to +10% (i.e. 216.2 - 253V) as compared with the 'old' limits of 240V ±6% (i.e. 225.6 - 254.4V). However, the former 220V countries (most of Continental Europe) have limits of 230V -10% to +6% (207 - 243.8V).
The Electricity Safety, Quality and Continuity Regulations 2002, which came into force on the 31st January 2003, replacing The Electricity Supply Regulations 1998, formally confirm the UK standardised supply voltage tolerances at 230V -6% to +10%.
Plans to harmonise the whole of Europe to 230V ±10% (i.e. 207 - 253V), which were due to be applied from 1st January 2003, have been postponed until 2008 at the earliest. Despite this postponement, any equipment intended for use anywhere in Europe and carrying the 'CE' mark will have to be capable of working over this wide range. Furthermore, the Institution of Electrical Engineers recommended in a 1996 report that for safety all electrical equipment needed to be tested across the range 230V +10% to -14%. This allowed for the lower and higher limits plus an allowance of 4% for voltage drops within the installation.
More significantly, because the old UK limits of 225.6 - 254.4V lie almost entirely within the new limits of 216.2 - 253V, there has been no incentive at all for the suppliers of 415/240V nominal AC mains power to make a real change, just to 're-label' the supply nominal and tolerances.
(Intriguingly, there has been one example of a necessity for a 'real' change: 250V nominal (440/254V three-phase) supplies, found particularly in Scotland, are definitely outside the new limits, and in this case it has made sense to make a genuine reduction, not to 240V but to the new 230V standard.)
Effects on Equipment
The main effect has been that imported equipment which would previously have been made specially for the UK 240V nominal supply is now designed either for the new 230V nominal or in many cases European manufacturers have assumed that equipment really designed for a 220V nominal can continue to be supplied into what is, after all, now a nominal 230V area. Since the real voltage continues to be 240V nominal, however re-labelled, much imported equipment is forced to operate in the UK on a higher voltage than it would in its country of origin - in the case of more recently designed equipment by about 10V but older designs in continued production receive some 20V more.
There is a further problem with equipment of North American origin. Many US and Canadian manufacturers continue to design their 'export models' for 220V but also fail to take adequate account of the supply frequency being 50 Hz as opposed to their 60 Hz. This is particularly seen in the design of power-supply transformers incorporated in such products.
The effects vary according to the type of equipment. Over-heating can occur as incorporated voltage regulators have to work harder. Supply transformers which are designed with minimally sized iron cores can easily go into saturation, especially toroidal designs. This can cause circuit breakers to trip on the excessive inrush current. Incandescent lamps have a non-linear characteristic which means only a small over-voltage can reduce their life expectancy markedly.
In addition, power consumption is unnecessarily high. A resistive load subjected to a 5% overvoltage will consume 10.25% more power. Subjected to a 10% increase in voltage the additional power consumption will be 21%.
It is therefore always worth checking whether equipment will operate at a reduced voltage, with likely beneficial effects both on equipment lifetime and the cost of power consumed. In some cases, if the supply voltage tends to vary this strategy may not be possible as the voltage sags may take the supply below the minimum operating voltage of the equipment. In such cases, stabilising or regulating the supply voltage will enable the equipment to work correctly and will simultaneously allow the supply voltage to be chosen to optimise equipment life and also energy consumption.
Solutions
(a) Voltage Stabilisers
If a voltage stabiliser is fitted, the output voltage setting (usually 240V or more recently 230V in the UK) can be set down to 220V. Even the fact that recently supplied stabilisers will usually be factory preset to 230V rather than 240V will be a help in itself.
An important point is that the input correction range of a voltage stabiliser is relative to the set output voltage. For example, the very widely used Claude Lyons Series TS voltage stabiliser has an output voltage settable anywhere between 200V and 250V, and standard models have three tappings, providing input correction range, relative to the set output voltage, of -17½% to +7½% ('tap A'), ±12½% ('tap B'), and -7½% to +17½% ('tap C').
Originally intended to cater, at the same output setting, for the three conditions of (a) supply likely to vary more low than high, (b) supply likely to vary equally high and low, and (c) supply likely to vary more high than low, they can be used in conjuction with the output voltage setting capability to equalise the input acceptance range, as follows:
Output voltage setting Input range
240V Tap A input range (-17½ to +7½%): 198 - 258 V
230V Tap B input range (±12½%): 201 - 259 V
220V Tap C input range (-7½ to +17½%): 203 - 259 V
Thus by changing to tap C instead of tap A, essentially the same input range is provided with the stabilised output at 220V ' providing the advantages of reduced energy consumption and longer equipment life at no additional cost.
Because the automatic voltage stabiliser self-adapts, it overcomes the problems caused by the electricity generator reducing the supply voltage to limit demand at peak times.
(b) Distribution transformer tappings
If you have the luxury of 'importing' your electricity at medium voltage (6.6 or 13.2 kV for example) and have your own site distribution transformer, then you can probably also reduce the voltage for energy saving and equipment life prolongation without cost. Distribution transformers are usually fitted with primary taps at, for example, +5%, +2½%, 0%, -2½% and -5% and it may simply be possible to arrange to use taps for a higher nominal MV supply voltage, thus reducing the LV output voltage (e.g. 415V to 400V).
(c) Voltage reducing transformers ("energy saving transformers").
A so-called energy saving transformer is essentially nothing more than a single or three phase autotransformer with tappings providing lower output than the input. Typical transformers may provide tappings at 440/250, 415/240, 400/230, 380/220V for example, or percentage reductions of -2½%, -5%, -7½% and -10%, and it is easy to select a suitable reduction.
Some newly introduced transformer designs provide output tappings at -5, 6, 7 and 8%. However 1% steps are unnecessarily fine, and are probably intended to provide an unrealistic impression of 'high resolution' adjustment.
Three phase voltage reducing transformers can be wound so as to provide other features such as third-harmonic neutral current suppression and/or phase balancing ('static balancer', 'artificial star point' etc.)
It should be noted that energy saving transformers are only appropriate when the mains supply is stable. If the mains supply voltage were to drop, the effect of the transformer would be to reduce an already low voltage, possibly to the point where the load equipment fails to function.
Most publicity about energy saving transformers fails to mention this crucial point. A recent report by economic consultancy NERA for Powergen states that the UK could face power shortages as early as 2004. The report (see Financial Times 13 Jan 2003) says that closure of uneconomic, ageing plants and low investment because of depressed prices could lead to electricity shortages in a severe winter. NERA said evidence from generators on future closures and investment plans indicated that forecast peak demand would rise above available capacity by 2007. Unforseen breakdowns at power stations coinciding with severe weather, however, could mean problems arising earlier.
The likely result of such an eventuality would be that to reduce consumption the electricity generators would reduce the voltage during the period of peak demand. The potential problem caused by a fixed-ratio energy saving transformer continuing to reduce the voltage further is completely avoided by fitting an automatic voltage stabiliser instead (see 'a' above).
(d) Automatic tap changers and tap-changing transformers
A disadvantage, inherent in all tap-changing regulating devices, and absent from the continuously-correcting voltage stabilisers described in (a) above, is the sudden step change in voltage as taps are changed. In some applications this is not a serious problem, but there will be a sudden and disconcerting instantaneous change in illumination, in the image size of computer and video screens (and sometimes flickering and momentary loss of synchronisation), and in some cases a potentially damaging inductive kick.
Summary
To summarise, a modest voltage reduction, in the region of 5-10%, will produce a valuable reduction in energy consumption and cost and extend the life of many types of electrical apparatus. Where a voltage stabiliser or distribution transformer is fitted, this can be achieved at no cost simply by adjusting the voltage setting. In other cases, a suitable tapped auto-transformer, or a 'buck connected' transformer will repay its capital cost within months. However a fixed-ratio voltage reduction may cause problems if the supply voltage reduces, whilst a voltage stabiliser will automatically compensate for this, - and by providing a constant voltage optimise equipment operation and prolong it's working life.
Don't let them know or they might be after you :wink:
