In recent weeks, many South Africans experienced load shedding again after striking Eskom workers sabotaged the national grid.

Load shedding happens when Eskom’s power supply cannot meet demand, and the company shuts down power in a controlled manner.

This is done to prevent a complete grid blackout, where it would take weeks to get the country back online.

According to a City Press report in 2015, Eskom secretly conducted a nationwide blackout simulation to test how its systems would handle a total loss of power.

It tested areas such as emergency responses and how the crisis would be communicated to the public.

While there are no immediate threats of a total national blackout, load shedding is needed to avoid this scenario.

How a national blackout happens

Electricity expert Chris Yelland explained that the safety features built into electricity equipment to prevent catastrophic failure would lead to a blackout.

“When demand exceeds supply, what happens is you have overloading of generators, transformers, cables, and switch gear,” said Yelland.

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

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 still on, causing them to overload and trip – once again reducing supply.

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

“You cannot operate an electrical system where demand exceeds supply,” said Yelland.

Black start

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

This could take 2-3 weeks, said Yelland.

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. This matter has been carefully thought out and procedures put in place.”

A total blackout will be akin to civil war

Robbie van Heerden, a senior energy specialist at the CSIR and Eskom’s former general manager of the national electricity system operator, previously said a blackout would be a disaster “akin to civil war breaking out”.

He explained that during a blackout, darkness, no or minimal telecoms, water schemes running dry, social unrest, and looting would occur.

Western Cape Premier Helen Zille explained in 2015 that while generators will be able to provide some reprieve, their fuel will run out.

“Cellphone companies can no longer transmit signals. Radio transmitters also die. So do ATMs,” said Zille.

Sewage pump stations would overflow, and hospitals and clinics would also stop functioning, she added.

“The criminal justice system, including courts and prisons, would grind to a standstill. Public transport would come to a halt. Shops would close.”

“Life as we know it, in a modern economy, cannot function without electricity,” she said.

Now read: Load shedding will be a risk for the next five years