Total blackout risk caused “beyond stage 6” load-shedding, says analyst

Independent energy analyst Pieter Jordaan said South Africa came close to a national blackout after Eskom’s emergency reserves were depleted, forcing it to go beyond stage 6 load-shedding.

South Africa was suddenly dumped into stage 6 load-shedding last month, which surprised many people, including Electricity Minister Kgosientsho Ramokgopa.

Ramokgopa and Eskom’s generation head, Bheki Nxumalo, said the breakdown level at power plants should not have resulted in stage 6 load-shedding.

Even worse was that many people experienced far longer blackouts than expected under stage 6.

Energy analyst Chris Yelland said Eskom hit stage 8 power cuts according to the official national code of practice for load shedding.

Yelland said many people, including his family in Craighall Park, are experiencing 12 hours of load-shedding daily.

“If you look at the NRS048-9 specifications, they are consistent with stage 8 load-shedding. It is not stage 6 load-shedding,” Yelland said.

He explained that power cuts of 12 hours or more per day are a problem experienced by people across South Africa.

“The level of load-shedding of ten to twelve hours per day that we are experiencing is stage 8 load-shedding,” he reiterated.

Jordaan echoed Yelland’s view, noting increasing cases of “ration creep”, where load-shedding lasted longer than the planned schedules.

He revealed that Eskom drained its emergency reserves and lost its pumped storage capacity, forcing the power utility to implement load-shedding “beyond stage 6”.

However, because the government seems set against going beyond stage 6, Eskom did not officially announce it.

“Eskom had no more emergency resources to defend the increased demand, and the psychological stage 6 barrier meant that ‘ration creep’ was the only way out,” he said.

“Normally, in a major crisis episode, one would pick up an incursion into the 2.2 GW reserve, but there were no reserves to incur into — as these were already depleted.”

Jordaan added that Eskom’s latest performance and power data confirmed that Black Friday, which took place on 24 November, almost became “national blackout Friday”.

Eskom blackout warning

Eskom previously warned that South Africa’s power system is critically short of operating reserves, which poses a risk to the system’s ability to arrest frequency deviations and prevent a blackout.

Eskom generates and transmits alternating current (AC). Its generators are synchronised to the national grid at a frequency of 50 Hertz (Hz).

Power plants and household appliances can accommodate a slight variation of frequency changes without any reaction.

However, these changes are usually limited to a 1% frequency deviation. This equates to 0.5 Hz in South Africa — 49.5 Hz to 50.5 Hz.

This is known as the dead band, where frequency changes can be accommodated without changes in plant output.

Any changes to the frequency of more than 1% will cause the plant to produce more or less power to bring the frequency back.

It will switch off if the frequency cannot be returned to within the dead band. This is a safety feature that is built into the design of the plant.

Therefore, Eskom closely monitors the grid’s frequency to ensure it does not fall outside the dead band.

Eskom’s “Medium-Term System Adequacy Outlook 2024–2028” report showed that the frequency regularly fell outside the dead band in 2022.

In 47 cases, the frequency dropped below 49.5 Hz, and in 12 cases, it exceeded 50.5 Hz. In December 2022 alone, it fell outside the dead band twelve times.

Eskom explained that ancillary services, also known as reserves, play a crucial role in ensuring the system is within the frequency band.

These reserves are also necessary to support renewable energy integration, particularly the integration of intermittent resources.

“However, actual reserve provision is underperforming, indicating a power system critically short of operating reserves, which poses a risk to the system’s ability to arrest frequency deviations,” it said.

The table below from Eskom’s “Medium-Term System Adequacy Outlook 2024–2028” shows the “frequency incidents” outside the 49.7 Hz to 50.3 Hz frequency band last year.

The frequency incidents that fell outside the dead band and posed a risk to the system are shown in red.

Date Under 49.5 Hz 49.5 Hz to 49.7 Hz 50.3 Hz to 50.5 Hz Over 50.5 Hz
January 2022 2 134 64 0
February 2022 2 150 65 0
March 2022 5 141 32 0
April 2022 4 91 64 0
May 2022 3 126 41 0
June 2022 4 177 155 3
July 2022 4 136 131 3
August 2022 4 97 58 1
September 2022 6 345 113 1
October 2022 3 156 43 2
November 2022 2 155 48 2
December 2022 8 210 33 0

This article was first published by Daily Investor and is reproduced with permission.

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Total blackout risk caused “beyond stage 6” load-shedding, says analyst