An Ausgrid worker has died after being electrocuted in Sydney's Lower North Shore.

Robert Nicholls, 39, was part of a crew replacing a low-voltage power pole in Lane Cove on Tuesday when he was shocked.

He was taken to Royal North Shore Hospital in a critical condition but died on Wednesday, according to the Electrical Trades Union.

“Our thoughts are with his family, friends, and colleagues at this tragic time,” union secretary Justin Page said in a statement.

An Ausgrid spokeswoman expressed sympathy and said the company had offered assistance to Mr Nicholls’ family.

“We are providing support and counselling to his colleagues who were on site with him on the day,” she said in a statement.

“The safety of our own people and the public is our number one priority and a SafeWork NSW investigation into the incident is already under way.”

The death comes two days after formworker Christopher Cassaniti, 18, was crushed to death when 15-metre high scaffolding collapsed on him and a co-worker at a construction site in Macquarie Park.