These images show how a Norfolk electricity station would look if energy bosses get permission to double its size.

National Grid has lodged plans for a 12-acre extension of the Norwich Main Substation, south of the city - and say it could take two years for the work to be completed.

The electricity company 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.

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

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

They say the height of the extension and equipment will be similar to what is already there and that no new overhead lines or pylons will be required.

Eastern Daily Press: Plans for the Norwich Main Substation sitePlans for the Norwich Main Substation site (Image: National Grid)

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.

National Grid has not revealed the cost of the scheme.

But it says the up-front cost will come from shareholders and borrowing, with the cost passed to customers through electricity bills over the next 40 years.

Eastern Daily Press: The current substationThe current substation (Image: Google Maps)

A National Grid spokesman said: "Our Norwich Main Substation has been in service for around 50 years.

"To connect the Hornsea Project Three offshore wind farm, and the Equinor Sheringham Shoal and Dudgeon wind farm extensions we now need to extend the site and install more equipment to increase capacity."

Public consultation over the plans took place before Christmas and National Grid said that had been considered when putting the plans together.

Some preliminary work has already started under permitted development rights.

The proposed extension is the latest in a number of electricity infrastructure projects in Norfolk.

READ MORE: What is the building work near the A47 near Norwich?

Plans for a 114-mile line from Norwich to Tilbury and proposals for power lines from Lincolnshire to west Norfolk have triggered opposition, including from campaign groups, councils and MPs.

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