South Africa’s State-owned electricity utility Eskom has approved a new five-year generation strategy, premised on an ‘80:10:10 principle’, which implies average plant availability of 80%, with unplanned outages limited to 10% and scheduled maintenance also set at 10%.

This meant that Eskom would, for the first time, undertake “long-duration planned maintenance” during the coldest winter months.

However, divisional executive Kannan Lakmeeharan highlighted the fact that the 10% planned maintenance level would be spread over a full operating year. In other words, there would be trough maintenance periods, of around 2 000 MW, in winter, and peak periods, of around 8 000 MW, during the summer months of November and December.

CEO Brian Dames announced the new operating parameters together with a commitment to higher levels of ongoing planned maintenance at a ‘State of the System’ briefing in Johannesburg on Monday.

The announcement came against a backdrop of a volatile power-station performance over the first four months of 2013, which had resulted in about 6 500 MW of capacity, on average, being unavailable on most days as a result of unplanned events.

These unexpected outages resulted in the deferment of some summer maintenance, leaving a maintenance backlog of 23 units by the end of March.

Disruptions to Cahora Bassa imports together with the unplanned outage of Koeberg Unit 1 were key contributors to the volatility. But the Exarro strike also resulted in some reductions as Eskom sought to conserve coal stocks at the Matla, Arnot and Matimba power stations. Coal stocks had since recovered to an average of 47 days.

The immediate target was to stabilise unplanned-outage levels to 4 500 MW to create the space for the winter maintenance programme.

Achieving such stability assumed that the power-station fleet would revert to its historical pattern of operating at higher availability factors during the winter months, on the back of improvements made during the summer maintenance programme.

BEAT THE PEAK

Dames said the utility aimed to overhaul at least nine of its generation units between April and August, despite a “tight” system balance, and appealed for residential and business consumers to help it in “beating the peak”.

South Africa consumed about 3 000 MW more electricity between 17:00 and 21:00 every night than was the case during the rest of the day. However, Eskom needed to produce at close to those levels even during off-peak times to be in a position to meet peak demand.

The utility was forecasting a 2013 winter peak of 36 800 MW against installed capacity of around 43 000 MW.

Dames outlined four beat-the-peak steps, including: switching off all geysers and pool pumps for the duration of the four-hour peak; switching off all nonessential lights; finding alternatives to electrical heaters; and citizens responding to the Power Alert messages broadcast on several television channels.

Should four-million South Africans switch off their geysers during peak hours, Eskom estimated that 2 000 MW of demand would be shifted, which would be sufficient to stabilise the system.

However, work was also under way to secure non-Eskom supply from municipalities and independent power producers and to continue with a range of other demand-side measures. However, some of these would be halted or curtailed in future as a result of the revenue reductions confirmed by the National Energy Regulator of South Africa in its review of Eskom’s tariff application for the five-year period from 2013 to 2018.

Dames insisted that Eskom would do all in its power to avoid a total black-out, even resorting to rotational load-shedding should the system come under severe strain.