Electrical maintenance works costing about £10m are taking place in St Helier.
High voltage cables are being fitted from Southill to the Esplanade.
It means Southill will become the hub of electricity in the island, linking the grid to the power station at La Colette.
Chris Ambler, chief executive of Jersey Electricity, said the works could cause some problems on the roads around the town centre.
Mr Ambler said: "We've given advanced warning that the project will take about three weeks.
"We have made very good progress, we have done four or five days of work on this already.
"We are hopeful to get the work completed a little bit earlier but it is going to be about two or two and a half weeks."