An investigation is under way into how a digger carrying out flood defence works in Gloucestershire pulled down a power line, cutting power to 800 homes.
Sparks from the cable set light to a field on Cinder Lane in Fairford, but local residents put out the flames before fire crews arrived.
The Thames Water team was working on a £2.5m flood alleviation scheme when the accident happened on Tuesday.
The water company has apologised to residents affected.
Power supplies to their homes were restored late on Tuesday evening.