Plans to double the size of an electricity station have triggered concerns from heritage watchdogs over its impact on a 19th century barn and cattle sheds.

National Grid has lodged plans for a 12-acre extension of the Norwich Main Substation, south of the city.

But officers at government advisor Historic England are concerned about the scheme's impact on a Grade II-listed set of buildings at Mangreen, to the north of the application site.

The 19th century barn and cattle sheds at MangreenThe 19th century barn and cattle sheds at Mangreen (Image: Google Street View)

The barn, at Hall Farm, was built in about 1800, while the cattle sheds are mid 19th century. They were listed in 1987.

Historic England officers say there could be "some harm to the significance of this designated heritage asset through changes to its setting", with the substation extension visible from those buildings.

The watchdog is not objecting to the plans, but urges that there should be "strengthened" planting to screen the substation extension.

How the expanded Norwich Main Substation could lookHow the expanded Norwich Main Substation could look (Image: National Grid)

Historic England said there are other heritage assets in the vicinity, including Grade II* listed Mangreen Hall and Gowthorpe Manor House.

However, officers said there would be no substantive views of the proposed development from those listed buildings and that "any harm to the significance of Mangreen Hall from changes to its setting would be negligible".

National Grid says it needs to expand the size of the substation, near Dunston and close to the A47 and A140, to take in power produced by new offshore wind farms off the Norfolk coast.

National Grid bosses are hoping, if permission is secured from South Norfolk Council, that work to expand the substation, which would take up to 26 months, can start later this summer.

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Power from the Hornsea 3 offshore wind farm, and the Equinor Sheringham Shoal and Dudgeon wind farm extensions are contracted to connect into the new extension.

South Norfolk Council will make a decision on whether to grant permission for the Norwich Main Substation extension in due course.