Scientists comment on a power outage caused by an electrical substation fire that has caused Heathrow airport to close.
**Dr Robin Preece, Reader in Future Power Systems, University of Manchester, said:**
“An electrical substation takes electricity from the transmission grid (the big pylons) at very high voltage and transforms this to lower voltages so that it can be distributed through cables to homes and businesses. This is done using transformers which are filled with oil. The oil is a very good electrical insulator and is needed to stop the electricity sparking to places it’s not meant to go inside the transformer while it is operating during normal conditions.
“If there is a catastrophic failure of a component, this can cause a big electrical spark or flashover which is extremely hot and which can cause nearby things to catch fire. Unfortunately for a transformer, this can lead to the oil catching fire – which is why the fire can be so large and difficult to control. The whole substation would probably need to be switched off and de-energised in order to let firefighters safely deal with the blaze. You cannot fight a fire in an electrical substation that is energised. Certainly all of the equipment adjacent to the transformer on fire would need to be de-energised.
“Fires like this are not common at all, as equipment is monitored to check its health and the equipment gets replaced once it starts showing signs of age that mean it could be dangerous (for obvious safety reasons). Until the reports are completed by the equipment owners, it’s not possible to know the cause of the failure and the fire.
“The electricity grid will have sufficient alternative supplies to get pretty much everyone back on supply very quickly. There is a lot of redundancy built into the grid. The fact that the transformer was on fire would have led to a larger amount of disruption (due to the need to shut down the whole substation to fight the fire) compared to if it just broke down without catching fire – in which case you might never have noticed anything as we have sufficient alternative routes for the electricity to follow.
“This substation is one of many that supplies Heathrow, but it is not the only substation that provides power to Heathrow. I do not know, but perhaps it supplies some of the more critical services at the airport.
“To restore power, there will be some switching happening across the network to allow the electricity to find alternative paths to get to affected areas. We don’t run the system with all of these areas connected at once, as it helps to isolate problems to specific areas when issues like this happen. So the engineers will be reconfiguring the network so that the faulty bit is isolated, and to get the rest of the network reconnected to healthy parts again. A lot of this will be done using remote switching from a control room.”
**Dr Guy Gratton, Associate Professor of Aviation and the Environment, Cranfield University, said:**
“All airline flights must declare their destination and one or two “alternates”, which are airports they will go to in the event of problems at their destination. The UK has many large airports and flights have been diverting from Heathrow to airports at least as far away as Manchester. Alternates don’t have to be in the UK so for example Frankfurt or Schiphol may be used. With such a major airport closing however, there is significant risk of running out of capacity at those places.
“The absolute priority will of course be safety, with convenience to the passengers inevitably secondary to that. This is inevitably going to lead to significant disruption and frustrations.”
**Dr Komal Raj Aryal, Lecturer in Crisis and Disaster Management, Aston University, said:**
“This morning’s unprecedented incident at Heathrow Airport has forced us to urgently reconsider how we teach and govern risk management for operational continuity.
“The incident highlights how a localised disruption to one of the UK’s critical infrastructures can trigger cascading impacts across the globe.”
**Declared interests**
**Dr Robin Preece**: “I have industry funding from National Grid Electricity Transmission, and NESO. Numerous industrial partners also support the Supergen Energy Networks Hub (which I am deputy Director of). I previously acted as a technical panel member for Northern Powergrid. I was sponsored by EDF Energy Networks during my undergraduate degree (2005-2009) and National Grid Electricity Transmission during my PhD (2009-2013).”
**Dr Guy Gratton**: “No conflicts to declare.”
For all other experts, no reply to our request for DOIs was received.