National blackout – What happens if South Africa’s electricity grid fails

Eskom announced last week that South Africans should expect load-shedding to continue during the evening peak period throughout winter.

The power utility said that it expects some improvements from September 2021, but even then load-shedding will not be completely eliminated.

Eskom has explained that the reason it implemented rotational load shedding was to avoid a potential national blackout in South Africa.

Such a blackout would be no small matter, the company said, as it would take weeks to restart the grid if South Africa went completely dark.

When there is there is more demand for electricity on the grid than Eskom can supply, it overloads generators, transformers, cables, and switch gear.

To protect against the massive damage such an overload would cause, trip mechanisms are installed.

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

This 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 – once again reducing supply while demand remains the same.

Infographic on why overloading the grid would lead to a national blackout

Besides leaving the country without power, a national blackout would also leave us in a situation where Eskom would have to restart power plants without any electricity — or “black start”.

This could take 2–3 weeks and would be very costly to South Africa’s economy.

Power plants use some of the electricity they generate to operate equipment such as conveyor belts that feed coal into furnaces, so to start them up you need to start with a small generator.

To bootstrap a power plant, a small diesel generator is typically used to start up a larger generator, which in turn is used to start parts of the plant.

“There are procedures and protocols in place to do a black start,” energy expert Chris Yelland has said. “This matter has been carefully thought out and procedures put in place.”

More importantly, there are many protocols in place to prevent a national blackout.

At the end of 2019, when Eskom had to implement stage 6 load-shedding, it advised municipalities to adjust their load shedding schedules up to stage 8.

During stage 8 load shedding, consumers could be without power for 48 hours over four days, or 96 hours in eight days.

Infographic illustrating a black start

Now read: 3,513GWh – worth R4.95 billion – stolen from Eskom in six months

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National blackout – What happens if South Africa’s electricity grid fails