Big revelation about Eskom load-shedding

National Rationalised Specifications (NRS) Association of South Africa chairman Vally Padayachee revealed that Eskom never used its own guidelines and definitions of load-shedding stages.

Speaking to eNCA, Padayachee said that when load-shedding was first introduced, Eskom indicated it was 1,000 MW per stage.

Eskom published and distributed numerous documents which showed that each stage corresponded with how many thousands of megawatts were cut from the grid.

Stage 1 means up to 1,000 MW was cut from the grid, Stage 2 means up to 2,000 MW was cut from, Stage 3 up to 3,000 MW, and so forth.

However, Padayachee has revealed that Eskom never used this widely distributed guideline and definition in its load-shedding.

He said one stage of load-shedding could vary from 800 MW to 1,200 MW cut from the grid, which is behind the confusion around load-shedding stages.

Although Eskom has never announced load-shedding above stage 6, it has, on some days, cut more than 7,000 MW from the grid. That equates to stage 8 load-shedding.

More recently, the megawatts cut from the grid have often exceeded the official load-shedding stage that Eskom announced.

The discrepancy, Padayachee explained, is because Eskom is not using the “1,000 MW per load-shedding stage” guideline it is promoting.

The table below shows the discrepancy between Eskom’s load-shedding stage and how much power is cut from the grid.

New load-shedding rules

The National Energy Regulator of South Africa (Nersa) has published a consultation document detailing a revised load-shedding approach that allows for up to Stage 16 power cuts.

The new document is known as the third edition of the NRS 048-9 Electricity Supply – Quality of Supply: Code of Practice.

It provides load reduction practices, system restoration practices, and critical load and essential load requirements under system emergencies.

After finishing all consultation processes, the document will be reworked as the NRS 048-9 Code of Practice Edition 3.

It will then replace the current Edition 2 standing code that Eskom’s System Operator uses to define load-shedding stages.

Padayachee explained that they came up with an innovative, simple, and less confusing way to govern load-shedding.

The new regime means that 5% of electricity demand is reduced for each stage of load-shedding. Stage 1 reduces 5% of demand, Stage 2 reduces 10%, Stage 3 cuts 15%, and so forth.

The electricity demand is forecasted for every hour of the day using a formula described below, with sample values in brackets.

• Demand (25,000 MW) = Forecasted hourly demand (30,000 MW) + Reserve margin (2,500 MW) – Curtailment load (7,500 MW)

They will then divide the demand with supply, which will show a surplus, where no load-shedding is needed, or a shortfall, which requires load-shedding.

If the shortfall is between 0% and 5%, Stage 1 load-shedding will be introduced. If it is between 5% and 10%, Stage 2 will be implemented.

The new document accommodates up to Stage 16 load-shedding, which means demand exceeds supply by up to 80%.

The table below outlines the proposed reductions in load under each load-shedding stage for general and load curtailment customers.