Heathrow Closure

I would expect Heathrow to be mostly fed at 33kV from Longford while the fire was at North Hyde. The common feed to both is the National Grid switching site at Iver. Perhaps all output circuits from Iver tripped rather than Iver-Hyde 1/2 275kV circuits.  

I would expect Heathrow to be mostly fed at 33kV from Longford while the fire was at North Hyde. The common feed to both is the National Grid switching site at Iver. Perhaps all output circuits from Iver tripped rather than Iver-Hyde 1/2 275kV circuits.  

Given the various shambolic official responses about “needing to reconfigure” their power, it looks like all of the 3 internal 33kV substations at Heathrow (ie. within their site) had power on the Longford leg, but had lost power on the North Hyde feed. Probably no duty HV engineer to drive round and switch the RMUs. Really appalling. 

Interesting - any thoughts on why they would all be sat on the North Hyde feed in normal opereational mode and not distributed across the feeders e.g. 2 on North Hyde/ 1 on longford?

Although none of this answers the question as to lack of independant power back-up on the site.

It's odd as North Hyde SGT's were at 110% nameplate even two years ago -- see Appendix 1 and Appendix 2 in  https://www.london.gov.uk/sites/default/files/checked_westlondoncapacity_0.pdf