Photo by: Duane Daws
South African power utility Eskom has suffered a serious breakdown at its Apollo substation which receives electricity from the Cahora Bassa dam in Mozambique’s Tete province, according to sources in HCB, the company that operates Cahora Bassa.
Moises Machava, the technical director of HCB, said there was an explosion in an Eskom transformer which knocked out the number five converter bridge at Apollo, which is in Centurion, near Pretoria. The bridge has three transformers, but if one ceases to operate, the whole converter bridge can no longer function.
The immediate result of this was to switch off Cahora Bassa’s pole one. No damage was done to the Cahora Bassa equipment, Machava said, but it could no longer supply the Apollo sub-station with about 900 MW of power.
That situation lasted for about an hour, and the sudden loss of 900 MW must have worsened the chronic power cuts which South Africa has been suffering due to Eskom’s inability to meet current demand.
When Cahora Bassa pole one was up and running again, it could only supply Apollo with 700 MW. The damage to the converter bridge meant that it was impossible to send the full 900 MW down the transmission line.
Machava said HCB was sending the other 200 MW to South Africa via Zimbabwe. This was a much longer route and there would inevitably be more transmission losses.
An Eskom spokesperson confirmed that the Apollo substation had been knocked out at about 7.45am on Wednesday and that the loss of power had been partially restored by 9.20. She said the loss had been about 1 300 MW rather than 900. This could perhaps be because power from other sources also passes through the substation.
She said that because the loss of power was off-peak, it had not aggravated load-shedding.