07 September 2008
Department for Innovation, Universities and Skills (DIUS)
 
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Quality and Continuity Of UK Electricity Supply

National grid pylon

The Department for Business Enterprise & Regulatory Reform (BERR) 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%. This is set to change to 230 volts +/- 10% (207 to 253 volts in 2008, this having been postponed from 2003). This change is due to the harmonisation of voltages across Europe and consumers are unlikely to experience any appreciative electricity supply changes when this comes into effect. It is likely this will further improve competition within the electrical equipment retail outlets, as manufacturers are able to benefit from these common voltage ranges.

Major power failures have occurred world wide, with significant load losses in Europe and the USA (1. Italy September 2003, 57 million people affected, cause – tree striking 2 interconnectors in Switzerland, 2. East Coast US August 2003, 50 million people affected, cause – again initial failure due to tree contact, 3.Western Europe November 2006, 10 million people affected, cause – transmission line switched out to allow passage of ship led to system overload). Failures in other parts of the world e.g., New Zealand (Auckland cable failures February 1998, 1 million people affected, 6 days without power in Auckland) are less dramatic due to the population affected but impact can be as significant economically. Within the UK major failures have been rare, (Hurricane 1987, 1.5 million people affected, 1 million restored within 24hrs) and failures generally affect a smaller number of the population and are restored relatively quickly. Important lessons are learned from post failure analysis and from 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 trees growing too close caused the large amount of damage to overhead lines.

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. This amendment actually comes into force on 31st January 2009 (6 years after implementation of Electricity Safety, Quality and Continuity of Supply Regulations 2002 (31st January 2003)) and electricity companies have to comply by this date. There is therefore significant preparatory work for stakeholders to undertake prior to this date and BERR are actively monitoring progress on this.

The Regulations should be read in conjunction with BERR’s guidance notes:

Consumer complaints regarding the quality or continuity of supply should be directed to energywatch in the first instance.

Primary responsibility for this public health matter is with the Department of Health. For information, please refer to the Department of Health: Electromagnetic Fields web page.

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