The Department has a duty to ensure electricity supplies are reliable and meet voltage and frequency standards. At present in the UK, domestic supply must be within the voltage range of 216-253 volts, which is +10/-6% of 230 volts. This is set to change, once agreement between all stakeholders is agreed, to 230 Volts +/- 10%, as this will further support voltage standardisation across the rest of Europe.
Some historical major power failures have occurred in recent years in mainland Europe:
- In 2003, 57 million people were affected by a tree striking two interconnectors in Switzerland.
- On the east coast of the US, again in 2003, 50 million people were affected by tree contact with power lines.
- In Western Europe in 2006, 10 million people were affected by transmission lines switched out to allow passage of a ship, which lead to a system overload.
In the UK, however, major electricity failures are very rare. Even though the 1987 hurricane affected 1.5 million people, one million had power restored within 24 hours. Failures generally affect smaller numbers and are restored as quickly as possible.
Severe storms in Britain are the most common cause of widespread power loss, and analysis of such events shows how important it is to manage trees near overhead lines. Working with the electricity industry and other groups, we amended the Electricity Safety, Quality and Continuity Regulations 2002 in October 2006 to ensure trees are kept clear of overhead lines. You can read the original regulations and subsequent amendments here: