Heathrow ‘back-up systems’ not designed to run full operation

Heathrow has explained how its “back-up systems” are not designed to allow the airport to run a full operation after a fire at an electrical substation was said to make it look “vulnerable”.

Europe’s busiest airport, which is supplied by the North Hyde electrical substation in west London, was forced to shut down after a power outage caused by a fire on Thursday night.

A spokesperson for the airport said it had no choice but to close Heathrow until 11.59pm on Friday, adding that it expects “significant” disruption over the coming days.

Later on Friday, Heathrow said in a statement the airport’s back-up energy systems worked “as expected” when the substation fire started.

It said: “We have multiple sources of energy into Heathrow.

“But when a source is interrupted, we have back-up diesel generators and uninterruptable power supplies in place, and they all operated as expected.

“Our back-up systems are safety systems which allow us to land aircraft and evacuate passengers safely, but they are not designed to allow us to run a full operation.

“As the busiest airport in Europe, Heathrow uses as much energy as a small city, therefore it’s not possible to have back-up for all of the energy we need to run our operation safely.

“We are implementing a process which will allow us to redirect power to the affected areas, but this is a safety critical process which takes time, and maintaining safety remains our priority, so we have taken the decision to close the airport for today.”

Energy Secretary Ed Miliband said that National Grid told him they had not seen “anything like the scale” of what happened with the “seriousness” of the fire.

“But it makes Heathrow look quite vulnerable and therefore we’ve got to learn lessons, as I say, about not just Heathrow but how we protect our major infrastructure,” he told ITV’s Good Morning Britain.

Mr Miliband said the fire “appears to have knocked out a back-up generator as well as the substation itself”.

He told BBC Radio 4’s Today programme: “It’s too early to say what caused this but I think obviously we will have to look hard at the causes and also the protection and the resilience that is in place for major institutions like Heathrow.”

The National Grid website says one of the main roles of substations is to convert electricity into different voltages.

Substations contain the specialist equipment that allows the voltage of electricity to be transformed, National Grid said.

National Grid owns more than 300 large substations, where 275kV and 400kV overhead power lines or underground cables are switched and where electricity is transformed for distribution to surrounding areas.

Dr Paul Cuffe, assistant professor, UCD School of Electrical & Electronic Engineering, University College Dublin, said an airport such as Heathrow requires a lot of electricity to operate – equivalent to a large town.

“As such, it would be typical for an airport like Heathrow to be given a dedicated connection from the substation at Hayes; there is likely a dedicated power line and transformer there that connects the airport to the wider grid,” he said.

“When a major fire severs that link, it will no longer be possible to bring bulk electricity to the airport.

“I would anticipate that a major airport like Heathrow would have some on-site emergency capability to ride through a grid disturbance; I would hope that the traffic control tower and runway lights weren’t totally plunged into darkness.

“However, processing planeloads of passengers requires Heathrow in its totality to consume a town’s worth of electricity, and the inability to meet this requirement is likely why flights had to be cancelled.”

Dr Cuffe said that from time to time substation equipment will fail and downstream power outages will result.

“One could argue that a critical piece of national infrastructure like Heathrow deserves special grid connection arrangements to secure its supply of electricity further,” he said.

“For instance, sometimes critical loads like this are fed from two separate substations to provide redundancy when outages happen.

“I am not familiar with the exact connection arrangements for Heathrow Airport but neither set-up would surprise me.

“It is ultimately a political and economic question to determine the right level of capital investment into grid infrastructure to avoid the problems that outages like this cause.”

Professor Richard Dawson, from the School of Engineering at Newcastle University, said: “This event has highlighted the vulnerability of our infrastructure to cascading failure.

“Damage to one asset in our energy network has exposed the vulnerability of our critical national transport infrastructure to major disruption.”

He said it is “surprising” that there is “no resiliency in the system” such as a back-up power source.

“Government has been repeatedly warned of the risks of cascading failures by a number of agencies,” he added.

“For example, the Climate Change Committee has highlighted how extreme weather events, such as flooding, heatwaves and storms, have caused similar cascading failures.

“As our society and economy are increasingly dependent on continued electrical and digital systems, there is an urgent need for a more joined-up Government approach to manage cascading failures such as this.”