Grid's maintenance record under attack as another power cut hits

The electricity regulator is to investigate allegations that the recent blackout in London was caused by a failure of maintenance by National Grid Transco, the power network operator.

The claims - by National Grid employees - surfaced as the main railway station in Birmingham, New Street, suffered a power failure yesterday afternoon.

National Grid insisted it was not at fault, a statement disputed by Network Rail, which had to suspend services from the station for 90 minutes.

The allegations on the London blackout contradict reports by the company and Ofgem, the regulator. These blamed human error for a crippling power failure in the capital on 28 August. The Grid's report, backed later by Ofgem, said the cause was a single wrong fuse fitted on a circuit.

However, two engineers working for National Grid have now said the ultimate reason for the blackout was an oil leak, which the company had not tackled "for weeks". The claims were made on BBC Radio's Today programme.

The programme also claimed to have documents that pointed to a systemic problem at National Grid in carrying out maintenance duties, including critical work, across the electricity network. An internal document, obtained by the BBC, referred to a "work request black hole".

The two employees, whose identities were not revealed, said the network was beset by lack of staff to carry out work. National Grid has halved the 7,000 workers it had since it was privatised in 1990.

The electricity regulator said: "We have listened to the [Today] programme with great interest. Ofgem is very concerned by its content and will be reviewing the information that the BBC has given us."

The version of events presented by the employees contrasted with the initial assessment by Ofgem. If the allegations are correct, it could be damaging to the regulator, analysts said, as it is responsible for ensuring that adequate money is spent on the electricity infrastructure.

On 30 September, Ofgem's managing director for competition and trading arrangements, Boaz Moselle, said: "It is clear from our investigation that these power cuts were isolated incidents on the National Grid. While they were very regrettable for those affected, customers should not see them as signs that the network is suffering from lack of investment."

Yesterday Ofgem promised that the new information would feed into its inquiry into the blackout, which will produce its final report later this year.

The 28 August blackout severely disrupted the capital's transport system. National Grid, led by chief executive Roger Urwin, found that the London network had been shut down because of an incorrect fuse fitted on a power line. It was a one-amp fuse, rather than five-amp, and so it was unable to handle a surge of power through it when a second power line had to be shut down, leading to a switch of its load on to the first line.

National Grid dismissed the allegations from the BBC programme that it was the problem with this second line, which stemmed from an oil leak, that was the real cause. Nick Winser, National Grid's director of transmission, said switching was common, "perfectly sensible" and could have occurred "for any number of reasons".

He said that, had the right fuse been fitted on the first line, there would have been no problem. He said the oil leak was a "very distant" factor, adding that the fact that this problem was not corrected for several weeks was "normal". On 28 August the leak triggered an alarm, which shut down its power line.

Mr Winser also said that, while there was a "small" backlog of work, it would be cleared by Christmas. He said a centralisation programme, that has seen National Grid's records computerised, had "unsettled" some staff.