South Africa

South Africa at risk of total blackout

Energy expert Professor Anton Eberhard has warned that Eskom’s decision not to refuel its diesel open cycle gas turbines (OCGTs) increases the risk of a system failure.

Eberhard is the director of Power Futures Lab at the University of Cape Town’s Graduate School of Business.

Over the weekend, Eskom confirmed that diesel tanks at its OCGTs run have physically run out and are empty.

The power utility added that the tanks will not be replenished until 1 April 2023 as its spending overrun on diesel to date is twice the budget for the current financial year.

Eskom, responding to questions from Chris Yelland, said it has not ordered additional diesel and has no outstanding orders.

What it means, in simple terms, is that the Eskom OCGTs will be unavailable until at least 1 April 2023.

Eskom’s new OCGT power stations are intended to be used during peak periods and emergency situations to supply electricity to the national grid.

Without operational OCGTs, Eskom cannot respond to emergencies, increasing the risk of a system collapse.

Eberhard said Eskom’s decision not to refuel its diesel OCGTs removes 2,067MW from rapid response resources available to the system operator.

“At a time of intermittent and declining coal plant output, it increases the risk of more load-shedding and system failure,” he said.

He added that the cost of unserved energy for South Africa’s economy is much higher than the cost of running the Ankerlig (1,327MW) and Gourikwa (740MW) OCGT diesel plants.

“It is mad economics for Eskom to stop fuelling these due to regulatory constraints. The ministers are asleep again,” he said.

“The president will need to intervene. It is not a good idea to go into the ANC December conference with these power sector risks and levels of load-shedding that anger people.”

System failure and a total blackout

System failure and a total blackout occur when the frequency of South Africa’s alternating current supply gets too high or too low.

The system operates at 50 hertz (Hz). When this frequency goes too high or too low, you have a significant risk to the system.

Safety features designed to protect the equipment against catastrophic failure will cause a cascading trip-out if the grid becomes overloaded.

When demand exceeds supply, you have an overloading of generators, transformers, cables, and switch gear.

Trips are installed to prevent massive damage in the event equipment is overloaded.

If there is an overload and equipment starts to trip, the overall electricity supply decreases, but the demand stays the same.

It places even greater strain on the parts of the grid that are still on, causing them to overload and trip if you do not act quickly.

If you had an aerial view of the country, you would see these cascading trip-outs spread as a wave of darkness sweeping the country.

Besides leaving the country without power, a national blackout would put Eskom in a position where it needed to bring power back online from scratch – a “black start”.

This process can take between two and three weeks, which will cause havoc across South Africa.

Power plants use some electricity they generate to run equipment like conveyor belts that feed coal into furnaces.

To start these up, you must begin with a small diesel generator to bootstrap the rest of the power plant.

The small generator generally starts up a larger generator, which fires up the rest of the plant.

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