230MW/460MWh Uskmouth BESS

On the site of the former Uskmouth coal-fired power station near Newport in South Wales, the 230MW/460MWh Uskmouth Battery Energy Storage System (BESS) is one of the largest battery projects built in the UK. Uskmouth BESS is a partnership between global investment manager Quinbrook Infrastructure Partners and E.ON, which took a 50% stake in the project in 2024. Construction began in November 2023 on the site's former coal stockyard.

Rather than build a new grid connection, the project reuses the existing 230MW connection into the 132kV substation, providing a new lease of life to the area. The two-hour duration system provides fast-response, dispatchable capacity to the grid, and forms the anchor of a wider plan to redevelop Uskmouth into a Sustainable Energy Park. We supplied the two 120/140/180MVA 132/33kV Wilson Power Transformers that link the site's 33kV battery system to the 132kV grid.

Each transformer is fitted with a vacuum on-load tap changer (OLTC) for voltage regulation, giving stepped voltage regulation across a ±10% range under live load to keep the connection stable as battery output swings between charging and discharging. The units carry a full online condition-monitoring package including oil and winding temperature monitoring, Buchholz and pressure-relief protection, and dedicated valves and sampling points for dissolved gas analysis (DGA). This ensures that the transformers' health can be tracked continuously in service.

Following delivery to the Newport site, our engineers carried out the mechanical erection of both transformers. Our team positioned the radiators and conservators and connected the prefabricated pipework, followed by pre-commissioning, including visual inspection, insulation-resistance testing and sweep frequency response analysis (SFRA). Each transformer was supplied with its own AVR control panel to control the tap changer remotely. We have also provided a comprehensive package of strategic spares, from bushings and cooling fans to a spare tap-change control relay to support long-term, reliable operation.