The need for network reinforcement

Grain to Tilbury is a proposed grid upgrade, requiring the replacement of the existing 1960s Thames Cable Tunnel between Tilbury, Thurrock, and Gravesend, Gravesham, alongside a new headhouse connection point at both ends of the tunnel. These headhouses are needed to connect the tunnel and serve as access points.

The project is part of the UK’s transition to a net zero future. It will be a vital upgrade to the existing local electricity transmission system in Kent and Essex: places where large amounts of renewable and low carbon energy are scheduled to connect in the coming decades.

The Thames Cable Tunnel is an existing high-voltage electricity cable beneath the Thames between Tilbury and Gravesend. It was built in the 1960s and houses 400 kV transmission cables between substations at Tilbury and Kingsnorth as part of National Grid’s high voltage transmission network.

The cable which currently delivers electricity under the river Thames between Tilbury and Gravesend has been in operation for over 60 years and is in need of replacement in order to deliver the objectives of The Great Grid Upgrade and aid the move to net zero. A new tunnel is the most effective way to deliver a long-term upgrade to the local network.

A number of options were considered as an alternative to building a new tunnel. These included maintaining the existing tunnel, or replacing it with a crossing tower over the Thames. Both options present challenges including impacts on important and sensitive bird habitats, and a lengthy consenting process required to secure the works, particularly with the existing overhead line which would require a development consent order (DCO). The outages needed to facilitate the refurbishment of the existing tunnel also mean that it would take a considerable amount of time to deliver.

Therefore, a new tunnel is being developed as this is considered to be the most effective and safest option. The tunnel will help to ensure a continued safe and reliable supply of electricity to the area.

How the need for network reinforcement is identified

NESO leads an annual cycle which looks at how much energy needs to be carried on the network in the future, and where network capability needs to be improved to accommodate that.

This process is to ensure that efficient, coordinated and economical proposals are brought forward.

In planning and operating the network we must comply with the National Electricity Transmission Security and Quality of Supply Standard. These set out criteria and methodologies for planning and operating the network in Great Britain – in essence, minimum requirements designed to ensure secure and stable electricity supplies.