Power cuts due to 'fuse' error

A single "fuse" which was wrongly installed caused the power cuts that plunged parts of London and the South East into darkness last month, it was disclosed today.

National Grid said an over-sensitive automatic protection relay disconnected supplies to three power stations on August 28, leaving about 410,000 homes and businesses without electricity.

In its report on the power failure published today, the company said it was "the largest loss of supply from National Grid for over 10 years".

Combination of events

The power failure resulted from a combination of events which began when the national control centre received an alarm from Hurst power station in Kent at 6.11pm.

According to the report, the alarm indicated that a transformer at Hurst was "in distress and could fail, potentially with significant safety and environmental impacts".

The transformer had to be shut down, leaving Hurst supplied only by the sub-station in Wimbledon, south-west London, via another in New Cross, south-east London.

But seconds later, the change in power flows was interpreted as a fault by automatic protection equipment.

This automatically disconnected New Cross, Hurst and part of Wimbledon from the rest of the transmission system, causing the loss of about 20% of total London supplies.

Power was restored to all sub-stations within 37 minutes, the report said.

National Grid said it had informed Scotland Yard that the power failure was "a system incident with no third party involvement".

Following an investigation, National Grid found the second fault occurred because a fuse was wrongly installed, shutting down the system when it should not have done.

Inquiries

The Government has announced that it is to hold an inquiry into the London power cuts.

It will also investigate the blackouts in the West Midlands last Friday, as well as the one at the end of August which stranded hundreds of thousands of travellers in London and the South East.

Energy Minister Stephen Timms said he had decided that further work needed to be done to look into the wider issues surrounding the power cuts.

An investigation by watchdog Ofgem is also under way to examine whether National Grid or the distribution companies concerned breached their legal obligations to develop and maintain secure electricity networks.

Ofgem said it expected to publish an initial assessment of the London and Midlands' incidents by the end of this month.

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