Infographic: Load-shedding explained

WEB_PHOTO_LOADSHEDDING GRAPHIC 3_09122014

When Eskom implements load shedding, it does so in different stages, on a rotational basis from 2-4 hours to protect the electricity grid from collapse.

JOHANNESBURG - When the lights go off and you can't cook or watch TV, we know that Eskom is most likely load-shedding. But what do these two words really mean?

According to Eskom, load-shedding is "done countrywide as a controlled option to respond to unplanned events to protect the electricity power system from a total blackout.

"While we generally use the word blackout loosely to mean “no lights” in our local area, a country-wide blackout has much more serious consequences, which can occur when there is too much demand and too little supply, bringing the power system into an imbalance – tripping the power system in its entirety."

"Many countries and cities in other parts of the world have experienced complete blackouts. To re-start their system, they are able to tap into a power system from a neighbour which can take a few hours or days, but we have to rely on ourselves to start the system from scratch – energising one power plant at a time and one section of the country at a time. 

"It could take up to two weeks to restore full power, which would have a severe impact on our country! This is why we use load-shedding, or load reduction, to effectively manage our power system and assist in protecting it from such an event."

Understanding Eskom Load-shedding stages

Load-shedding will be used under emergency conditions for limited periods.

Four schedules have been developed based on the possibility of risk and to ensure that load-shedding is applied in a fair and equitable manner:

  • Stage 1 allows for up to 1000 MW of the national load to be shed.
  • Stage 2 allows for up to 2000 MW of the national load to be shed.
  • Stage 3 allows for up to 3000 MW of the national load to be shed.
  • Stage 4 allows for up to 4000 MW of the national load to be shed.

Load-shedding will be implemented in most instances in 2-hour blocks.

  • However, in Eskom-supplied Johannesburg areas, blocks are 4 hours long. This is to coincide with City Power’s 4-hour schedule.

Each of the time periods has an additional 30 minutes added to allow for switching of networks in a way that will not damage the power system.

  • Most customers (those in 2-hour blocks) may, therefore, be without electricity for up to 2.5 hours at a time, while customers in 4-hour blocks may be without electricity for up to 4.5 hours at a time.

Eskom will begin load-shedding customers at the start of the period (for example from 06:00) and will have all scheduled customers switched off within the first half hour (that is, by 06:30)

At the end of the period, after the two / four hours (that is, by 08:00 or 10:00 as applicable), Eskom will start returning power to customers and should have them all back within half an hour (that is, by 08:30 or 10:30).

The frequency of load-shedding increases as higher Stages are used

  • Stage 1 requires the least amount of load-shedding, 3 times over a four day period for two hours at a time, or 3 times over an eight-day period for four hours at a time.
  • Stage 2 will double the frequency of Stage 1, which means you will be scheduled for load-shedding 6 times over a four day period for two hours at a time, or 6 times over an eight day period for four hours at a time Stage 3 will increase the frequency of Stage 2 by 50%, which means you will be scheduled for load shedding 9 times over a four day period for two hours at a time, or 9 times over an eight day period for four hours at a time.
  • Stage 4 will double the frequency of Stage 2, which means you will be scheduled for load-shedding 12 times over a four day period for two hours at a time, or 12 times over an eight day period for four hours at a time.

If more load needs to be shed than has been scheduled in Stages 1, 2, 3 and 4 then National Control will instruct additional, unscheduled load shedding. This means you may be shed outside of your scheduled times.

* The information above is provided by Eskom.