By Antonio Ruffini, Editor ESI-AFrica

22 April 2013 – Usually South African electricity provider Eskom reduces the planned maintenance on its generation fleet in winter to minimum levels, instead undertaking this work during the lower peak demand summer months. However, the winter of 2013 will be different. South Africa’s national power provider will continue to maintain at least nine generation units out of its total of 81 between April and August to ensure the long term sustainability of its fleet. This will put additional pressure on South Africa’s already constrained electricity system.

Minister of public enterprises Malusi Gigaba says that since September 2012 there has been deterioration in Eskom’s power station performance, and higher rates of unplanned outages have impacted on existing maintenance programmes.

In addition both he and Eskom CEO Brian Dames observe that the link that supplies power from Cahora Bassa to South Africa has become unreliable. Flooding that affected a transmission line as well as the failure of a smoothing reactor at Songo substation reduced supply from that source from 1,500 MW to 650 MW (with occasions when supply dropped to zero) over recent months. The capacity of the link was back at 1,300 MW as of the 22nd of April 2013, but nonetheless Dames says it has become an unreliable source of electricity for South Africa.

Further exacerbating the difficulties Eskom faced during the summer was an unplanned outage at one of the 900 MW Koeberg units, with this returning to service in mid-late April. The strike action at Exxaro mines that supply Eskom power stations with coal also had a negative impact on generation by up to 1,000 MW a day as stations were operated in such as way so as to conserve stockpiles. In addition, coal quality issues affected certain power stations, in particular Tutuka, which meant it ran in such a way as to reduce negative effects from burning coal that had up to 45% ash content.

All this means that while Eskom’s maintenance backlog was reduced from 36 units in January 2012 to 23 units at the end of March 2013, it has become impossible to further delay maintenance until the summer. Some units will be out for up to 120 days for planned maintenance during the winter. Both Dames and Gigaba say that the stage has been reached where plant reliability cannot be further compromised.

The plan for the next five years is for Eskom to achieve a fleet availability of 80%, with 10% planned maintenance and 10% of unplanned maintenance.