Supply Voltage
Since 1960, the supply voltage in UK domestic premises has been 240 V AC (RMS) at 50 Hz. In 1988, a Europe-wide agreement was reached to unify the various national voltages, which ranged at the time from 220 V to 240 V, to a common European standard of 230V (CENELEC Harmonization Document HD 472 S1:1988).
The standard nominal supply voltage in domestic single-phase 50 Hz installations in the UK is still 240V AC (RMS), but since 1 January 1995 (Electricity Supply Regulations, SI 1994, No. 3021) this has an asymmetric voltage tolerance of 230 V+10%−6% (253–216.2 V), which covers the same voltage range as continental 220 V supplies to the new unified 230 V standard. This was supposed to be widened to 230 V ±10% (253–207 V), but the time of this change has been put back repeatedly and as of 2007 is set for 2008 (BS 7697). The old standard was 240 V ±6% (254.4–225.6 V), which is mostly contained within the new range, and so in practice suppliers have had no reason to actually change voltages.
Read more about this topic: Electrical Wiring In The United Kingdom
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