21 February 2013 – Eskom reports that its nuclear power station Koeberg Unit 1 tripped automatically late on the afternoon of Wednesday 20th of February 2013, due to a fault in an electrical switchboard. The utility says the fault is being investigated and the unit will be returned to service as soon as possible. Unit 2 at Koeberg continues to operate at full power.

The reduced supply from Koeberg has put added strain on a power system which was already tight because of reduced imports from Cahora Bassa in Mozambique and volatile plant performance. One of the transmission lines from Cahora Bassa in Mozambique was damaged by the flooding of the Limpopo River and the capacity available from Cahora Bassa has been reduced to approximately 650 MW, from 1,300 MW previously. HCB (the operator of Cahora Bassa) and Eskom are working to restore the line to full capacity.

The performance of Eskom’s generation fleet has been volatile, reflecting the fact that it does not have enough space to achieve the sustained levels of planned maintenance which are needed to improve the reliability of the power. As a result the power system in South Africa is extremely tight at present, particularly during the evening peak hours between 18h00 and 21h00.

This is illustrated by the fact that on Thursday 21st of February the capacity available to meet that evening’s peak demand was 31,803 MW (including open cycle gas turbines) while demand was forecast to be 31,438 MW. Planned maintenance stood at 2,882 MW and unplanned outages at 7,603 MW.