A 500 MVA transformer at the Midas substation, in Gauteng, tripped in the evening of December 11, disrupting electricity supply to about 15 mines in the Carletonville, Fochville and Potchefstroom areas, as well as to residential customers. State-owned utility Eskom says in a December 12 update that its technical teams acted swiftly and have managed to restore essential load to the mines, enabling limited operations.