Overhead power lines in Teesside and County Durham are to be refurbished and sections replaced at a cost of £15m.
National Grid plans to overhaul about 16 miles (25km) of electricity wires between Hartlepool and Murton which were put up in 1962.
The work, which includes maintenance on 82 pylons, will start in August and is expected to take a year.
Project Manager Martin Bage said it was an "important" part of the development of the local energy network.
"We'll be engaging with local communities to ensure they're aware of what's going on if it's likely to affect them directly but we expect any disruption to be very minimal," he said.
The company said the electricity supply would not be disrupted and notice would be given of any road and footpath closures.
National Grid owns and operates the high-voltage electricity transmission network in England and Wales.