Another explosion at the Mayfair Substation, on Monday, left residents in the dark.
City Power said the fire department contained the fire and cordoned off the area.
It must first be declared safe before technical teams can re-enter the station.
The cause of the second explosion is unknown and a thorough investigation is underway, to determine the cause of the first explosion.
Affected areas extend to the SABC in Auckland Park, Garden City Hospital in Mayfair, as well as businesses and residential customers in Mayfair, Crown, Vrededorp, Brixton, Crosby, Pageview, Homestead Park and Amalgam.
Picture: Supplied