050910 Electricity pylons carry power from Cape Town's Koeberg nuclear power plant July 17, 2009. South Africa will need 20 gigawatts (GW) of new power generation capacity by 2020 and would require double that amount a decade later to meet rising demand, the country's power utility said September 7, 2009. Picture taken July 17, 2009. REUTERS/Mike Hutchings (SOUTH AFRICA ENERGY BUSINESS)

Cape Town - Eskom is shedding load, as demand for electricity countrywide outstrips the state utility’s ability to supply.

Power supplies are yet again at critical levels, with three sets of issues hampering Eskom’s ability to generate enough to cope with the demand.

One of the Koeberg Nuclear Power Station generating units tripped slightly more than a week ago, while floods in Mozambique brought down one of two supply lines from the Cahora Bassa Hydroelectric Scheme and the second supply line had “issues”, said Eskom spokeswoman Hillary Joffe.

A third problem was volatility in the generation by coal-fired power stations in the summer heat of the northern areas, where full capacity generation was preventing sufficient planned down time and maintenance, she said.

So far, load shedding has been done strictly according to plan, affecting only large single customers, such as steel producers, mines and smelters.

But Joffe conceded that generation capacity was already at marginal levels, similar to those of January 2008 when blackouts swept across the country in waves.

“We are dealing with three sets of issues. The fact that the Koeberg unit is down has left us without its 900MW on the system.

“The input from Mozambique is usually 1500MW but we are now only getting 650MW from there because of the line brought down by the floods and the issues on the other.

“The Mozambicans are working hard to fix that and at Koeberg we are pulling out all the stops to get the unit up and running.

“The third issue is that the performance of our other power stations is very volatile in summer.

“Many are dry-cooled and that becomes a problem when day temperatures are high. This is compounded by the fact that, due to the demand, we are not able to shut down units for planned maintenance as often as we would like to.”

Joffe could not say what had caused Koeberg’s Unit 1 to shut down.

But independent observer Chris Yelland, publisher of an energy newsletter, said a lot must have been wrong for it to remain down so long.

“A week in terms of a shutdown at a nuclear power station is a lifetime,” he said. “The fact that it is taking them longer than that to sort it out must mean there was something big going on,” he said.

Cape Argus