Heathrow Closure

I have seen reports of the cost to Heathrow airport for the incident being in the region of £20m - with costs to the wider industry and economy boutne by others.  Given that Heathrow has grown organically with demand being added over decades, i wonder how much of the situation arose because the problem became too big to solve. 

All supplies to the site were connected to a single feeder - my initial thought was to wonder why the load was not distributed across the avialble feeders, but if it would have taken half a day to reconfigure the supplies, with multiple system shut downs required then perhaps a reconfiguration was deeemed not feasible or not palatable.

Looking at the cost - If there are wide spread loads (critical and non-critcal) that are not generator backed across the site, then a project to cover these with generators would cost tens of millions - probably in excess of the quoted £20m loss to 'Hetahrow Airport Limited'.  Perhaps there was always an awareness of the risk but a conscious decision not to mitigate 

chrisbryant said:

Heathrow has grown organically

A common feature of a failure trajectory.

See [1] for accident trajectory diagram (fig 6.3, p149) showing how we bounce along the boundaries of acceptability and safety.

I think flights stop taking off at arund midnight or just before and incoming flights start arriving at 4ish so not a huge window of opportunity.  Maybe the required programme for such works would push the costs beyond the realms of what was deemed palatable - especially if the cost of an enforced outage to reconfigure the supplies in a big-bang moment is only £20m

I wasn't suggesting that everything needed to be done in one night. There is such a thing as staging over weeks or months. 

What happens when the airport has to close because of bad weather (example Fog).

My wife experienced a situation many years ago when her fight into London was delayed because of bad weather and her plane was diverted into a airport in Scotland for a few hours.

Just think what happens when the local clocks are changed in spring and fall and the airlines are forced to adjust their schedules.

Peter Brooks

Palm Bay FL

Not sure what happened at Heathrow but for sure the emergency lights worked and presumably the control tower standby generator but security devises in passport control and computers were probably run off the airports mains power circuits which were not backed up with emergency generation.

Same with the baggage handling equipment.  Hopefully, Heathrow have by now installed these critical areas with standby plant as it certainly should not cost as much as £20 million.

Have a look in this thread for one of my previous post with attachment where I simply put

Worth a read

The cost to the Heathrow reputation is 10 times more than the stated financial cost of £20m.  It is also worth looking at who were the decision makers and who has just sold off a large share of Heathrow airport from their portfolio. 

Final report published today https://www.neso.energy/document/363891/download 

Thanks Chris.

An interesting read (with some lessons in the detail) although sadly at the highest level does sound like the common "opportunities were missed" maintenance failure.

"Using forensic analysis from both National Grid Electricity Transmission and London Fire
Brigade, this review has seen evidence that a catastrophic failure on one of SGT3’s high
voltage bushings caused a fire to ignite on the supergrid transformer. This was most likely
caused by moisture entering the bushing causing a short circuit. The electricity likely then
‘arced’ (causing sparks) which combined with air and heat to ignite the oil, resulting in a fire.
2.4 An elevated moisture reading in one of SGT3’s bushings had been detected in oil samples
taken in July 2018. According to National Grid Electricity Transmission’s relevant guidance, such
readings indicate ‘an imminent fault and that the bushing should be replaced’. While the
reading was recorded in National Grid Electricity Transmission’s online system, the mitigations
appropriate to its severity were not actioned."

So that is the nature of the network fault, but, and it is quite a big but, why, given Heathrow has 3 in-feeds, could they not switch over to the other 2 and keep going - clearly that is what National Grid expected would happen as they did not consider the transformer bushing a priority - and presumably would have had to power some kit off to change it anyway.
Mike

If you mean the airport, with three infeeds, I'd say by the read of it they could (and did within 6-7 hours from memory) but it required manual intervention. Probably this was in part due to SSEN enforcing open points to ensure that their feeders aren't paralleled through the customer's network (usually this means transferrable key interlocks etc).

If you mean the Hyde 66kV SS, the first SGT tripped and the substation did indeed recover using the third SGT which was provided as a running reserve. But the fire caused the second SGT to trip a little bit later either due to fire damage to its control kiosk or exploding bushings, and the third SGT was taken out automatically by the control scheme as it wasn't designed to operate solo.

If you mean the airport, with three infeeds, I'd say by the read of it they could (and did within 6-7 hours from memory) but it required manual intervention. Probably this was in part due to SSEN enforcing open points to ensure that their feeders aren't paralleled through the customer's network (usually this means transferrable key interlocks etc).

If you mean the Hyde 66kV SS, the first SGT tripped and the substation did indeed recover using the third SGT which was provided as a running reserve. But the fire caused the second SGT to trip a little bit later either due to fire damage to its control kiosk or exploding bushings, and the third SGT was taken out automatically by the control scheme as it wasn't designed to operate solo.