The sub-station exploded, cutting local power supplies, after large amounts of metal including copper wiring were removed.
A recent spate of metal thefts has seen street-lighting cables and war memorials targeted around the country.
After the blast at 3.15am on an industrial estate in Oldbury in the West Midlands, police checked hospitals for patients with injuries consistent with electric shock and found the man suffering from 60 per cent burns.
The 21-year-old, thought to be Eastern European, was in a critical condition at Birmingham's City Hospital.
Police want to trace the driver of a private vehicle that is believed to have dropped him off at the hospital.
Detective Sergeant Carl Russell, of West Midlands Police, said: 'The man has suffered extensive burns from his ankles up to his scalp which are consistent with having been electrocuted. He remains in a critical condition. Read More