Vandals caused a power cut in parts of West Wiltshire on Monday evening when they threw tree branches over a 33,000-volt power line. Electricity was cut to about 7,000 properties in Trowbridge and Bradford- on-Avon for two hours as a result.
A spokesman for Southern Electric said the vandals could have been killed.
"You run the risk of serious injury or death because you only need to be close to the cable and electricity can jump gaps," he said.
"This sort of vandalism also puts engineers at risk," he added.