Mastodawn

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.

https://www.neso.energy/document/363891/download

Show thread

Steve Scott

@russss Haven't had a chance to sit down and read this until now. 7.16 (Fire suppression system installed in 2002 inop for at least 3 years) is a real popcorn moment.

Someone didn't flag a high moisture reading properly is some of those things that happens in large complex systems, but tagging out a fire suppression system for 3 years...

7.21 suggests that it might not have been enough anyway.