Eskom: If it isn’t the rain, it’s the heat

2014-09-21 15:00

On Thursday this week, Eskom experienced one of the highest levels of “unplanned outages” on record, about 7?000 megawatts.

It is the worst unplanned outage since the unexpected rains in Mpumalanga in March took out almost 10?000MW of generation when they turned Eskom’s coal into sludge; and the 8?500MW unplanned outage on May?15, which the company put down to the generally bad state of the power stations.

The warm weather meant there was no emergency declaration, and no power cuts were needed, even though it was precisely the heat that caused the Matimba power station in Limpopo to lose more than 1?000MW of its load, adding to this year’s already elevated level of plant breakdowns and load losses.

Eskom’s level of unplanned outages has been escalating sharply as the largely old fleet shows the strain of being run to capacity since the start of the power crisis in 2008.

Based on the twice-weekly System Bulletin published by Eskom, reported unplanned outages this year have averaged 5?129MW, 12% of Eskom’s theoretical capacity of about 43?000MW.

This includes the supply from the emergency diesel generators in Cape Town as well as power imports.

Compare this year’s figure with average unplanned outages in 2012 of 4?367MW and 4?996MW last year.

These outages have caused the delays in the all-important scheduled maintenance, which has been dropping as low as 2?000MW – the ideal should be about 4?000MW.

The lost generation on Thursday was caused by “high ambient temperatures and a westerly wind direction”, according to Eskom spokesperson Dikatso Mothae.

In an emailed response to questions, Mothae said: “Matimba is a dry-cooled station using air-cooled condensers to condense the process steam used to drive the steam turbines. The efficiency of these condensers is severely impacted by high temperatures

and worsened by westerly winds as the condensers are situated on the east side of the power station.

“This is an inherent design limitation at Matimba.”

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