Avonmouth
Current construction activity
| Date from | Date to | Activity |
| May 2021 | 2024 | Building and energising new pylons |
| 2020 | 2024 | Removing existing pylons |
| 2018 | Ongoing | Roadworks and traffic management |
| 2018 | Ongoing | Access to public footpaths and rights of way |
Overview – Autumn 2024
National Grid is in the final stages of completing the northern section of the Hinkley Connection route between Sandford and Seabank substations.
The new 400,000 volt line of lattice pylons in and around the industrial area of Avonmouth is complete including the construction and wiring of two new 76-metre tall lattice pylons on either side of the River Avon is complete. This followed the removal of two 91-metre tall pylons that had been in place for decades.
Other removal works in the area saw the line of pylons from Avonmouth village disappear, including the pylon from the playground at Avonmouth C of E Primary School and Daisy’s Nursery. Avonmouth C of E Primary School and Daisy’s Nursery.
We’ve used traditional lattice design pylons, to span the River Avon and navigate the turning angles in Avonmouth's industrial port. These works complete the northernmost section of the line to Seabank substation.
Modifying the existing network near Seabank substation
At Seabank, our main task, working with contracts J Murphy and Son, has been to modify and increase the capacity of the existing 400kV substation to enable the new overhead line connection.
To achieve this, we have removed a supergrid transformer (SGT) off the site, which is now being stored as a spare at Sundon. In its place we have constructed a gantry where the new Hinkley Connection overhead line connects into the substation. With the removal of the SGT, complex works to install underground cabling across the site was required to reconnect the existing 132kV and 400kV circuits onto different SGTs. This has now been completed.
Construction of a flood barrier wall is ongoing and will be the final stage of work to be completed at Seabank.
Avonmouth timeline
Completed September 2020
Modify Avonmouth substation and existing overhead line to the east of the substation
Work carried out:
Replaced a small section of overhead line to the north of the substation with underground cables.
Constructed a new cable sealing end (CSE) pylon to connect the underground cables to the overhead line.
Changes inside Avonmouth substation to enable the connection of the new underground cables.
Reinstatement work including removal of the temporary construction compound and part of the haul road.
To be confirmed
Modify Seabank 132,000 volt substation and the existing overhead lines at Seabank
What we're doing:
Building a temporary construction compound and temporary entrances and access roads to allow construction traffic to enter the undergrounding site from the local highway.
Undergrounding a small section of the three existing overhead lines at Seabank. This will enable the new overhead line to pass safely overhead.
Building three pylons to connect the existing overhead lines to underground cables.
Modifying Seabank substation to enable the connection of the new underground cables.
Removing the existing overhead lines that are no longer needed in this area.
Mid 2021 to mid 2024
Build new 400,000 volt overhead line
What we're doing:
Building temporary entrances and access roads to allow construction traffic to enter site from the local highway.
Building a new overhead line from Sandford substation to Seabank substation (approximately 31.2 km).
In this area, we'll use a mix of steel lattice pylons and T-pylons.
Mid 2021 to mid 2024
Remove the existing 132,000 volt overhead line
What we're doing:
Removing the overhead line from the A368 in Sandford to Avonmouth substation, which will make way for, and minimise the visual impact of, the new connection.
Removing a small section of the existing overhead line to the east of Avonmouth substation.
To be confirmed
Modify Seabank 400,000 volt substation
What we're doing:
Extending the existing substation to enable the connection of the new overhead line.
Modifying the existing site access road.
Removing unnecessary electrical equipment.
Installing a perimeter flood defence wall with flood gates around the substation to help guard against tidal flood risk.