The construction division originally secured the framework, with an estimated annual value of £30m-plus, in November 2014.
The extension, which is worth up to a further £60m, will run until October 2019 and will enable Western Power Distribution to maintain and enhance its electricity network.
Morgan Sindall will deliver planned and reactive works on Western Power Distribution’s 11kV to 33kV distribution networks throughout the West Midlands region, which includes Stoke-on-Trent, Telford, Tipton, Birmingham, Hereford and Ludlow, Worcester and Gloucester.