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 08 August 2007
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Quality and Continuity Of UK Electricity Supply

National grid pylon

The Department of Trade and Industry has a duty to ensure that electricity supplies are sufficiently reliable and meet minimum standards of quality in terms of voltage and frequency.  In Great Britain domestic supplies must be maintained within the range 216 volts to 253 volts, corresponding to a nominal value of 230 volts, minus 6% to plus 10%.

Major power failures have been a world wide problem since the earliest USA blackouts of the 1960's and important lessons have been learned by studying their causes.

Severe storms in Britain are the most common cause of widespread loss of supplies but analyses of such events have consistently shown the importance of good tree management near overhead lines. In October 2002, for example, in the aftermath of severe storms across southern England, consultants concluded the large amount of damage to overhead lines was caused by trees growing too close.

Working with the electricity industry and other interested groups, the Electricity Safety, Quality and Continuity Regulations 2002 were amended in October 2006 to ensure that trees are kept clear from overhead lines to improve storm performance.

© Crown copyright 2007