A programme of SSEN ground investigation works is set to begin tomorrow (Thursday) and take around eight weeks.
The company said the work would allow its teams to examine sections of the route connecting Shetland to the mainland energy system.
The investigations will take place between Kergord and Gremista, Kergord and Cul Ness, and Burravoe and the Beaw Field substation in south Yell, SSEN said.
The work is expected to be completed in early June, weather permitting, and will be carried out by specialist contractor BAM Ritchies.
Up to 25 people working across five teams will be undertaking the works, which will include drilling boreholes and excavating trial pits, as well as monitoring and conducting environmental and archaeological surveys where necessary.
SSEN said a team of environmental and archaeological specialists will ensure any environmental impact is monitored and kept to a minimum.
Temporary traffic lights will be in place on the A970 main road, and the B9071 North Mainland road, for short durations of one to two hours only, to allow the project to be carried out safely and to ensure disruption is kept to a minimum.
SSEN Transmission project manager Edward Holten said: “This is a key step in our plans to build the Kergord to Gremista and Kergord to Yell connections, which will allow us to investigate the ground conditions in the area to inform our final engineering design.
“Ahead of works we would like to thank the local community for their patience while we carry out these essential ground investigation works.
“We will work to keep disruption to a minimum at all times and apologise in advance for any inconvenience which may be caused.”