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Transformers: Explosion at Apollo substation cuts power from Moz

Apollo sub station
Apollo outdoor valves

On Wednesday, the South African-based Apollo substation, owned by state-owned power utility Eskom, suffered an explosion in one of its transformers.

The Mozambican Cahora Bassa hydroelectric dam exports electricity to the Apollo substation located in Centurion, close to Pretoria. According to technical director of the Cahora Bassa Hydroelectric Facility (HCB), Moises Machava, the explosion at Apollo cut out the number five converter bridge, the Africa News Agency reported.

Cause and effect

The bridge comprises three transformers and should a fault occur in one transformer, then the trio will not function at all.

Once the explosion was detected the Cahora Bassa pole one was immediately turned off.

According to Machava no damage was done to the Cahora Bassa equipment, but it could no longer supply the Apollo substation with an estimated 900MW of power.

The unexpected loss of 900MW would have had further impacted Eskom’s inability to meet the country’s power demand.

Once pole one was re-activated, the damage incurred only allowed the transmission of 700MW to Apollo.


Machava added that HCB was supplying the additional 200MW to South Africa via Zimbabwe. Due to the route being much longer, there would inevitably be more transmission losses.

According to an Eskom spokesperson, the Apollo substation was knocked out at around 7.45am on Wednesday but that the loss of power had been partially restored by 9.20am.

Eskom further said that the loss had been about 1,300MW rather than 900MW, due to power from other sources which also pass through the sub-station.

Ashley Theron
Ashley Theron-Ord is based in Cape Town, South Africa at Clarion Events-Africa. She is the Senior Content Producer across media brands including ESI Africa, Smart Energy International, Power Engineering International and Mining Review Africa.