Very nice report on the fire at North Hyde substation which took down Heathrow in March.
tl;dr:
* Fire was caused by moisture ingress in a high voltage bushing which was detected in 2018 but got lost in the system.
* North Hyde is an ageing substation which didn't have adequate protection against spread of fire
* Heathrow didn't think that a loss of grid feed was a plausible risk, so they assumed 10-12 hours was a reasonable recovery time from that.
Also missed that Heathrow published their own report last week:
Just to add: the GB electricity transmission system is still one of the most reliable in the world, with a reliability of 99.999930% last year. This incident hit a lot of holes in the swiss cheese, and I'm sure it will be learned from.
I'd rather it wasn't privatised, but National Grid Electricity Transmission is definitely one of the more successful of our privatised utilities. (Though I think at least some of the credit for that has to go to the regulator.)
I think the term we ought to be looking for is redundant. If one sub station goes down the other should be capable to taking over and supply the required power. This was not done. Given that GB electricity supply reliability is north of 99% that should have been easier to accomplish.
I hope the proposed Heathrow expansion does tackle this. It is incredulous. One substation takes down with it one crucial node in world wide travel.
Russ Garrett
Welkin