The £800m engineer, procure and construct framework is for design, construction and commissioning of 11 kV to 400 kV cable systems across National Grid’s network.
The agreement is set to last four years, with an option for a two-year extension.
Projects awarded will typically vary in value between £2m and £50m.
Morgan Sindall is one of four companies appointed; the other three have not yet been named.
A National Grid spokesman said: “We have not fully signed all of the cable framework contracts and as such have not issued a contract award notice.”
Morgan Sindall managing director of utility services Simon Smith said: “Morgan Sindall has been working in the electricity transmission market for a number of years and this opportunity further enhances our growing capability with National Grid and in this specialist sector.”