South Africa has been oscillating between Stage 2 and Stage 4 load shedding since Friday, cutting up to 4 000 MW from the national grid per day.
The rolling blackouts are expected to continue until Wednesday, with demand expected to taper off towards the end of the week, as Thursday is a public holiday.
Around 18 000 MW, or 40% of the power utility’s 46 292 MW of installed capacity, have been unavailable over the last few days due to generator plant breakdowns, a tropical storm in neighbouring Mozambique, and the unavailability of diesel to run the gas turbines.
Stage 2 moved quickly to Stage 3 and then Stage 4 on Saturday. Stage 2 continued on Saturday and Sunday nights, revealing serious issues with the power supply.
Fin24 spoke to Eskom’s acting head of generation, Andrew Etzinger, about the issues affecting the extremely constrained power system, which he referred to as a "perfect storm".
Tropical Cyclone Idai in Mozambique and Zimbabwe
The cyclone, which killed at least 166 people, made landfall over the Mozambican port city of Beira on Friday and moved on to Zimbabwe. The trail of wreckage cut power supply and communication networks in the area.
Mozambique is South Africa’s largest energy trading partner. Eskom receives 1 150 MW in power from the Cahora Bassa hydroelectric generation station, and the transmission line has been damaged by the storm. Etzinger said the power utility had not yet been able to access the site as there has been severe flooding. The level of damage will first need to be assessed before there is an indication of when this power source will return to the grid.
Boiler tube leaks, plant breakdowns
"Boiler tube leaks are not new. They are steadily increasing and they are a major cause of plant failures," Etzinger said. Eskom’s previous bouts of load shedding in November, December and February were also caused by plant breakdowns.
Eight generator units are currently down while boiler tube leaks are being fixed, according to Etzinger.
Etzinger said Eskom used to have an early detection system for boiler tube leaks so they could proactively find them, fix them and avoid lengthy stoppages. The contract for the system lapsed about a year ago and there has been a tender process to re-instate this. He added that the early detection system should be up and running again within a month.
For now, however, it takes the maintenance teams at the power utility approximately a week to fix a boiler tube leak. They first cool the boiler to gain access and then enter the area to cut the damaged pipes. Technicians then use very high precision welding techniques to reconnect them. After this takes another day or so to light up the boiler again to generate steam and re-start the turbines, Etzinger said.
Unavailability of diesel stocks
When coal generation units are offline due to maintenance or breakdowns, Eskom has the option of running diesel or gas turbines as an emergency measure and a at a higher cost. In recent days, the emergency reserves of diesel have been low.
Etzinger said a shipment is expected to arrive in SA on Tuesday which will bring some relief. The diesel will then take one or two days to offload before it can be used to power the turbines.
This extra generating capacity will coincide with demand falling on the public holiday on Thursday and towards the weekend on Friday. Etzinger foresees the power system remaining constrained, but improving towards the end of the week if there is no further deterioration in plant breakdowns.