Glossop Road and Clarkson Road are now open to traffic and pedestrians again following the blaze, which broke out at 9am.
Flames shot through a manhole cover and there was an explosion after a fire involving an underground electricity link box broke out.
The fire, on a pavement outside the Co-op on Glossop Road, developed as shocked pedestrians and motorists were passing by but nobody was hurt.
It was put out by firefighters using dry power extinguishers.
They said a number of substations had to be isolated to prevent them from being affected.