Murphy has been awarded a £35m contract to replace a high-voltage cable in south London.
The work, which is scheduled to start in November, will see the firm replace one of two high-voltage cables near Croydon.
Murphy will design the replacement 400 kV cable and install it underground in an existing tunnel that runs between Beddington and Rowdown substations.
As part of its package, the company will replace the ventilation and telecoms systems in the tunnel and test the cable once it is installed.
Work is scheduled to be completed by October 2020.
Murphy chief executive John Murphy said: “We have decades of experience installing cables, as well as building the tunnels that house them.”
In February Murphy bought Carillion’s UK power business, which has increased the company’s capacity to do pursue design and installation work on high-voltage cables.
Earlier this year Murphy revealed a fall in pre-tax margin from 3.6 per cent to 1.7 per cent for 2017, with problems on power projects in the North of England being partially blamed.