Following yesterday evening’s power failure at 6:20pm, affecting large parts of South London and parts of Kent, there was considerable disruption most obviously to underground and over-ground rail services.
National Grid Transco reiterates its apology to everyone affected by the disruption which was caused by a fault in the electricity transmission system. We are in touch with all the relevant authorities and a thorough investigation is underway.
An initial account of last night’s events and the action taken is set out below:
At 6.10pm yesterday evening an alarm indicated a fault on a transformer at our Hurst substation in Kent.
We switched the transformer out of service at 6.20pm, and power was still able to flow into London through other circuits.
However, quite exceptionally, another fault occurred within some seven seconds, stopping flows on a 275,000 Volt underground cable between our New Cross and Wimbledon substations.
At this point, electricity supplies to the affected areas could no longer be maintained and a power black-out followed. The problem was identified and within half an hour it was fixed and full power was restored to our transmission system.
Within some 15 minutes of this, London Electricity had completed progressively re-energising its system and normal power was restored in all areas.
The problem was totally exceptional.
At times we experience equipment failure, but its impact is imperceptible to everyone, since the back-up systems kick-in seamlessly. In this case, the back-up also failed.
At this point, we do not know the reason why the equipment failed.
Last evening, our focus was on fixing the problem and this we did within about 30 minutes. Today we are giving as full an explanation as we can of the events.
We know that our management systems worked exactly as planned and the duration of the black-out was short-lived.
This was a quite exceptional event in a transmission system which is modern, well invested, well maintained and has consistently demonstrated impressive reliability.
Finally, it should be said that there is absolutely no parallel between what happened in London yesterday evening and what happened recently in the US. There is no similarity in cause, scale or duration.
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