Johannesburg - A fire broke out at Eskom's substation in Secunda, Mpumalanga, the parastatal's media desk said on Wednesday.
One of the transformers was damaged by the fire on Tuesday.
Eskom was investigating the cause of the fire. Some residents of Secunda were without electricity.
"Eskom is working hard to restore power to the effected customers who do not have power," the media desk said.
Eskom was expected to release a statement on the incident.