£2,000 part caused London blackout
By Andrew Taylor Utilities Correspondent
Published: September 10 2003 13:48 | Last Updated: September 10 2003 13:48
The incorrect installation of a 1amp, instead of 5amp, relay protection unit costing just £2,000, was at the heart of last month's power cut which threw London's transport system into chaos, a report by National Grid revealed on Wednesday.
The unit is about the size of a shoe box and provides the same function as a fuse in household electrical equipment. It shut down a key section of London's electricity network, halting the London Underground and disabling traffic lights during the evening rush hour.
The investigation, by the country's electricity transmission operator, says the dramatic loss of power at 6.20pm on Thursday August 28 was caused by a combination of one-off events rather than a general failure of the electricity network.
Roger Urwin, National Grid's chief executive, said: "There was not a significant failure of management systems."
Stephen Timms, energy minister, has launched an independent investigation into the power cut which affected big areas of south London and parts of Kent. A separate blackout affected parts of the West Midlands on September 5.
Mr Timms said on Wednesday: "I am grateful to National Grid for the report that they have provided to me on the recent power cuts and the lessons to be learnt. However, I have decided in light of the report that further work needs to be done to look into the wider issues surrounding these power cuts."
Critics including Ken Livingstone, London's mayor, have blamed the power cut on deregulation and under-investment in the privatised electricity industry.
Mr Urwin said the blackout would not have a significant impact on [National Grid's] profits. The group operated 43,000 similar protection units on its network. It had surveyed 9,000 of these - about 20 per cent of this type of equipment - and had detected no other cases of incorrect installation, he said.
The events which led to 20 per cent of London's electricity supplies being blacked out began with scheduled summer maintenance work which meant there was already reduced capacity on the south London network on August 28.
An alarm at 6.11pm then revealed that gas had accumulated within oil used for insulation at an electricity sub-station near Bexley in Kent, requiring a transformer to be shut. This "temporarily left supplies dependent on a single transmission circuit from Wimbledon."
None of these events should have caused such a dramatic loss of power but for the protection equipment at the substation "interpreting the change of power flows, due to the switching, as a fault," said the National Grid.
At 6.20pm, automatic protection relay disconnected the remaining supplies, including to big customers such as London Underground and Network Rail. National Grid said power began to be return within six minutes but was not fully restored until 6.57pm. By then transport systems had been plunged into chaos which lasted well into the evening.
National Grid shares were up 1 per cent at 381-3/4p in afternoon trade in London. |
