Load-shedding back as plant outages force Eskom’s hand
Eskom implemented emergency stage one load-shedding on Sunday for the first time in more than two years as an unexpectedly high number of plant outages made it necessary to drop load to stabilise the system. The utility supplies more than 95% of SA’s electricity.
This is the first time since 2016 that load-shedding has been necessary, with the exception of a few days during which plants were sabotaged in industrial action earlier in 2018.
Load-shedding takes place when the reserve capacity is so diminished that the system is at risk of tripping.
The reason lies in Eskom’s deteriorating plant capacity — measured by the energy availability factor — due to unplanned breakdowns. The energy availability factor is a measure of how much of Eskom’s plant at any one time is available to dispatch electricity. Eskom’s target is for 80% plant availability.
But in recent months, the energy availability factor has been on a rapid decline, reaching 66% on Eskom’s last weekly available figures. The energy availability factor for the year so far is 73%. This is a significant decline on 2017’s 79%.
Eskom has said that the decline was due in part to planned maintenance "but also to unplanned events", such as the explosion at Lethabo power station in the Free State in early October, taking an entire unit out of service.
The trend has industry worried as unless Eskom is able to attain an energy availability factor of 75% over the next five years it will not be able to meet the energy needs of the country and load-shedding would again become a regular occurrence.
Eskom’s power stations are ageing and the mid-life refurbishment that should have been done has been deferred with the consequence that performance is deteriorating.
Coal shortages may soon worsen the energy availability factor. Eskom said on Friday that ten of its power stations have critically low stockpiles, with five having less than 10 days worth of fuel. While the grid requirement is for 20 days worth of stockpiles, Eskom has traditionally held about twice that amount.
Wet summer weather also tends to lower Eskom’s performance as coal does not burn as efficiently when it is wet.
The utility says it needs more than 4-million tons to replenish coal supplies at ten of its power stations. More than one million tons has already been secured.
Eskom has also resorted to running emergency diesel-powered stations to supplement supplies, an expensive process that will cost more than R1bn over the next four months.
Eskom hopes to fix the coal shortages by March 2019, ahead of the peak demand during the winter season.
The coal shortages date back to early 2017, when some of its suppliers, particularly companies owned by the politically connected Gupta family, consistently failed to deliver to contracted specifications.