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Pushing the Limits: Why load shedding puts even more pr...

Our Burning Planet

OUTAGES EXPLAINED

Pushing the limits: Why load shedding puts even more pressure on an ageing electrical system

Candles illuminate a house in Midrand, Johannesburg, during load shedding on 21 June 2022. (Photo: Felix Dlangamandla / Daily Maverick)

The frequent switching on and off of load centres is putting additional pressure on an already overloaded system, which is why you might still be sitting in darkness even after load shedding was meant to end.

Johannesburg’s power utility City Power’s ageing infrastructure is not coping with the demands of Stage 4 load shedding.

Communicating with residents through a  ward WhatsApp group, Nicolene Jonker, DA councillor in the City of Johannesburg, told residents on Monday that “City Power can’t cope with Stage 4 load shedding. Half the operators are busy switching load centres on and off every two hours for load shedding, and the number of substation trips from inrush current after load shedding is very high.”

Isaac Mangena, spokesperson for City Power Joburg agreed with her assessment, telling Daily Maverick that Stage 4 was putting too much strain on their resources, with some substations unable to return during restorations, leaving customers without power for a longer period.

“Load shedding has undesirable effects on the infrastructure which, by its nature, was never meant to be switched on and off at short intervals, and comes with it added financial pressures that we did not budget for,” said Mangena.

Mangena said that at the weekend they fielded more than 5,000 outage calls and by 6am on Monday, they were dealing with almost 2,700 calls — more than 2,000 of them in 24 hours.

Most of the outages have been backlogged since Friday, with Randburg, Reuven and inner-city areas hit the hardest most of last week and into the weekend. 

Residents have taken to social media to express their frustration and confusion about why they still do not have electricity outside scheduled load shedding.

Energy analyst and electrical engineer Chris Yelland explained to Daily Maverick that in a city like Joburg — or any large city — urbanisation and rising population increased the demand for electricity, which ramped up pressure on the circuits.

“Levels of housing density are constantly increasing and therefore the electricity consumption is increasing over time,” said Yelland, adding that non-payment (which is escalating as the price of electricity goes up) also puts pressure on the system.

Mangena said increased demand due to winter weather, rampant cable theft and illegal connections also added pressure to an already overstretched system.

load shedding
Car headlights are the only sign of illumination on the main streets of Midrand, Johannesburg during load shedding on 21 June 2022. (Photo: Felix Dlangamandla / Daily Maverick)

Now, all this — coupled with load shedding — causes circuit breakers to trip, resulting in mass outages in Joburg.

Yelland uses the example of water geysers, explaining that when there’s load shedding and the power is turned off for two hours in an area, all the geysers in the neighbourhood begin cooling down.

When the power returns, all those geysers switch on simultaneously, sucking up energy to reach the temperature set by the thermostat. 

“And that might be enough to push you over the limit of the circuit breakers,” said Yelland.

So once the power comes online, the current is higher than normal, which trips the circuit breaker. Someone has to physically go to the substation to close the circuit breaker, and there is already limited manpower, which causes delays in getting the power back.

Mangena said that “apart from the lost revenue during load shedding, we are also forced to pull technicians and operators from leave, and many are already fatigued”. 

“We are also forced to divide our resources between attending to outage calls and responding to the two-hourly load shedding switch on and offs.”

Mangena said they are “beefing up resources in our service delivery centres, with more operators added to ensure we respond in time with limited delays during restorations”.

He said that for safety reasons, no maintenance was done during load shedding. 

load shedding midrand
LED lights illuminate a house in Midrand, Johannesburg during load shedding on 21 June 2022. (Photo: Felix Dlangamandla / Daily Maverick)

“It’s all to do with the fact that the circuit breakers are running close to their rated value because of urbanisation, increasing population density, increasing electricity usage… and load shedding,” said Yelland.

“Which might be the final thing that causes you to push above the limit.”

Mangena said that in-rush currents, multiple cable faults, vandalism and overloading due to the cold weather are among the reasons for the trippings in most areas, especially after load shedding restorations. 

Poorly managed and ageing infrastructure

Mangena said “our mostly ageing infrastructure also cannot be ignored, and its wear and tear increases every time they are switched on and off at short intervals”.

Yelland said that if we had well-maintained, relatively new equipment, switching on and off regularly shouldn’t be an issue.

“When you have old equipment that is under-maintained — with the oil in the transformers not clean, the insulation weakened with temperature and time, and moisture getting into the cables and into the joints and into the switchgear — you’ll find that that switchgear is weakened… the cables are weakened.”

This means that frequent switching causes critical damage to that equipment, which can result in system failures. 

“That’s just a sign of an ageing, poorly maintained network,” said Yelland. “Which is exactly what we have in South Africa in many, many municipalities.”

Councillor Beverley van Reenen, Mayoral Committee Member for Energy, City of Cape, said: “The City of Cape Town’s infrastructure is generally well maintained and maintained to the required standards. It is thus not the reason for secondary tripping. 

“Among the main reasons for extended outages after load shedding in City-supplied areas are as follows: Secondary tripping in some pockets of larger areas mostly occur due to excessive demand. When power comes back on, tripping happens as electrical equipment such as geysers all come on at the same time, not having been switched off prior to load shedding. 

“In addition, vandalism under the cover of load shedding is an increasingly common phenomenon as criminals strip substations and kiosks. These actions cause outages.

“Lastly, switching stations were not designed for load shedding. Most of the switching in City-supplied areas is done remotely and upgrades to switching station equipment continues to ensure the timeous switching during load shedding.”

Eskom strikes threaten Stage 8

On Sunday, Eskom announced that Stage 4 load shedding is anticipated to continue until at least midnight on Wednesday due to “unlawful and unprotected labour actions” at several power stations, which have caused delays in carrying out planned maintenance and repairs.

Business Maverick reported that thousands of Eskom employees had been striking and protesting after wage talks deadlocked last Tuesday. 

As Eskom is deemed an “essential service”, the strike is unprotected — which means workers who down tools can be fired.

Union sources and Eskom confirmed to Business Maverick on Monday that the strikes and protests were continuing.

Eskom says this illegal strike is putting about 4,000MW of generation capacity at risk.

Yelland said that if we lose another 4,000MW, SA is at risk of Stage 6 to Stage 8 load shedding. He explained that 4,000MW is four stages of load shedding, since each stage is 1,000MW. 

Mangena said that “with Eskom’s unprotected strike seemingly far from over, we are in fact preparing for the worst…”

He urged customers to switch off heavy appliances during load shedding. 

“This include geysers, pool pumps, heaters, stoves. These can be switched back on, gradually, a few minutes after restorations.” DM/OBP

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Absa OBP

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  • I remember being told in a lecture 60 years ago that it was dangerous to switch off the supply at a substation. It needed a fireproof suit and helmet, and a long handle. Things were inclined to melt. I believe that’s no longer the case, the switchgear is more sophisticated. Perhaps Chris Yelland can explain?

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