Storms can mean disruption and unpredictability for our electricity system. As owners of the network in England and Wales we take the job of ‘keeping the lights on’ very seriously, and we have a number of approaches in place to deal with potential issues that severe weather might cause – from power cuts to pylon damage.
Power cuts caused by severe weather can be more common on local electricity networks, which are managed by distribution network operators (known as DNOs), which is why certain areas may experience power cuts during a storm but the rest of the country doesn’t.
The part of the network that we deal with is the transmission system – the physical system that we use to move electricity at high voltage across the country. So we do a lot of meticulous preparation to guard against power cuts occurring on a national level and ensure that electricity continues to flow to reach the local electricity networks.
When planning how we manage the network, our engineers and analysts consider every detail that might impact how electricity is delivered around the country. This means that weather is one of our most important considerations, especially at times of year when we know we’re likely to face inclement or severe conditions.
Our transmission system must be resilient to storm conditions. We work all year round to ensure we’re ready, investing around £1.3 billion each year to adapt and develop our network. This includes upgrading and maintaining equipment, and routinely checking on the condition of our assets and the environment around them.
In the lead-up to a storm we initiate our response teams, which take the form of bronze, silver and gold command depending on how severe the situation is. The actions they take include:
reviewing staffing plans, both in the field and in our control room
evaluating the network status and, if practical, look to return assets earlier than planned to make the network more resilient
collaborating with other industry parties, such as the National Grid Electricity System Operator (ESO) and DNOs, to understand our collective resilience and things we may need to manage together
putting temporary generators and flood defences, additional teams and helicopters on standby
diverting teams and resources away from planned work in case they are needed to assist
reviewing weather forecasts based on multiple weather prediction models.
Engineers and operations teams from National Grid Electricity Transmission (as well as Scottish and Southern Electricity Networks, and SP Energy Networks in Scotland) make sure the network of pylons, cables and substations is robust against weather damage and a wide range of faults.
They respond to issues during the event and follow up at all sites to complete damage assessments.
Our engineers in the field are in constant contact with our Transmission Network Control Centre (TNCC), who remotely control the operations of the high-voltage electricity transmission system in real time.
The TNCC control room operates 24 hours a day, 365 days a year. They monitor around 4500km of overhead line, over 300 substations and around 1450km of underground cable, to locate any faults or issues and take appropriate action to ensure that electricity continues to flow.
As well as managing network issues, the TNCC also coordinates with key customers who connect to our network – such as the DNOs – before and during the event. They are also connected to any emergency calls with the wider industry, like Ofgem or BEIS, to provide critical network updates and support where needed.
The TNCC is also in constant contact with National Grid ESO, a legally separate part of National Grid that balances supply and demand in the system. They monitor the weather and prepare by anticipating different scenarios to make sure they have enough electricity reserves available for unforeseen losses of supply or generation.
Mechanisms designed to protect the system include delayed auto reclose (DAR), which kicks in if a fault trips a circuit (not uncommon during bad storms) and brings the powerline back into service after a few seconds. During Storm Arwen in November 2021, around 45 circuits tripped with the DAR automatic protection kicking in immediately.
We also offer to assist the DNOs at a local level where possible, providing key resources to support them in re-connecting supplies to communities and infrastructure such as hospitals. This may include deploying technical staff or use of our helicopters to identify damage.
Other contingencies are in place too. For example, colleagues at Thorpe Marsh substation in Doncaster set up 1.5km of temporary flood defences to successfully shield it from unusually severe floods.