Supergrid transformers travel by road and river to reach National Grid substations

Supergrid transformers collectively weighing over 1,300 tonnes have been delivered to substations across National Grid’s electricity transmission network in the first half of the year, as part of infrastructure upgrades designed to enable connections and boost resilience.

A 174-tonne supergrid transformer (SGT) arrived in Bridgwater substation in Somerset in May, having travelled on boat from Rotterdam, sailed up the River Parrett and been manoeuvred by specialist teams through Bridgwater town to the nearby substation.

The Bridgwater upgrade is part of National Grid’s Hinkley Connection Project, which is increasing the substation’s voltage from 275kV to 400kV to reinforce the network in the region in anticipation of future demand growth.

Just days later a similarly sized SGT arrived at Tilbury Docks en route to a new grid supply point (GSP) substation being built in Suffolk as part of National Grid’s Bramford to Twinstead Reinforcement project – a journey that took 10 hours through the night and was completed with minimal disruption.

Tilbury Docks was landing point for yet another SGT earlier this month – this one heading through the night via the M25 before arriving at Willesden substation in West London. The SGT’s installation will progress the Willesden and Kensal Green Connection project to reinforce the network in readiness for National Grid to connect a new data centre in the area.



Two giant SGTs are also planned for delivery in June to National Grid’s Elstree substation in Hertfordshire, as part of works to ensure continued safe and reliable electricity supplies in the region as demand grows.

The deliveries follow two SGT arrivals in February at the new Biggleswade substation – which National Grid is building to provide a new connection for UK Power Networks – and a new SGT which manoeuvred through London’s streets and into City Road substation in January.

Supergrid transformers are vital high voltage devices which boost substations’ capacity and resilience, stepping voltage up or down so electricity can be efficiently transmitted from power generators or safely distributed to homes and businesses via regional networks.

With each SGT weighing the equivalent of around 30 African elephants, and similar in size to a double decker bus, deliveries are a feat of logistical planning – requiring coordination with local and highway authorities, and often a police escort. Specialist firms such as Allelys, Collett and Mammoet are normally used to move SGTs around the country.

Roisin Quinn, director of asset operations at National Grid, said: “A lot of work goes into transformer deliveries, long before any electrons pass through them. Multiple teams across National Grid and its supply chain are involved in moving and installing these huge devices in a way that minimises disruption.

“These recent and upcoming SGT deliveries are all contributing to significant upgrades we have underway on our transmission network, and will all reinforce the grid as electricity demand grows and projects connect in the future.”

National Grid has installed and energised over 20 supergrid transformers in the last five years to upgrade its network and connect a range of generation and demand initiatives, from wind farms to rail electrification projects and distribution network connections.