More than 37 substations in the Coventry area have been attacked by metal thieves in the past week, Central Networks said.
The energy provider said thieves stole safety equipment and left substations open, causing an electrocution risk to any children who wandered inside.
It has offered a £5,000 reward for information leading to a conviction.
West Midlands Police said stealing metal from substations was extremely dangerous and people had died doing it.
Pc Dick Neale, of West Midlands Police, said: "People in other parts of the West Midlands have died as a result of getting a massive electric shock after stealing metal from a substation.
"Not only that, it leaves the substations, which are normally well secured, open to the public, where anyone including children could wander in and be electrocuted."
Officers are visiting scrap metal dealers to try and trace the stolen metal and offenders.
The substations, carrying at least 11,000 volts of electricity, were the target of thieves who ripped out copper earthing, which is used to protect people from electrical shocks.
Phil Wilson, customer operations manager at Central Networks, said: "These thieves continue to risk life and limb for the sake of scrap metal, behaviour which not only presents a huge inconvenience to those who may suffer power cuts, but which can leave behind a potentially dangerous situation."