The explosion occurred when an 11,000 volt live cable was struck within an excavation.
Ioan Boboc, 22, a construction operative from northwest London, suffered burns over 60% of his body when he and other workers were using breakers and a shovel within the excavation at the corner of Charing Cross Road and Tottenham Court Road on 2 December 2008.
Mr Boboc died of his injuries on Christmas Day 2008.
Southwark Crown Court heard that the contractor had not informed workers that there were live cables in the excavation and that the company had failed to put adequate measures in place prevent them from coming into contact with the cable.
Birse Metro Ltd of Station Road, Redhill, Surrey, pleaded guilty to breaching Section 3(1) of the Health and Safety at Work etc Act 1974. It was fined £167,000 and ordered to pay £43,000 in costs.
After the hearing, HSE inspector Lisa Chappell said: "The dangers associated with live underground cables are well-known to those carrying out groundworks in the construction industry. Clear guidance on avoiding contact with them is freely available to companies undertaking this work.
"This incident highlights the absolute necessity for such work to be properly planned and managed. Operatives should be briefed on the presence of cables and a safe system of working should be robustly enforced. Mr Boboc's family continues to grieve the loss of a son and brother following an incident that could have easily been prevented."