On Monday (23/2), residents of numerous northern suburbs were left stranded after transformers exploded, sparking a fire and causing significant disruption to the electricity supply network. Power outages affected homes and businesses, leaving many without electricity for hours.

By Wednesday, electricity had been fully restored in the affected areas after technical teams from Mangaung’s power utility were dispatched immediately and worked continuously to identify and resolve the fault, resulting in the successful restoration of supply.

Speaking at a media briefing on Wednesday, Centlec CEO Malefane Sekoboto said: “The transformer that exploded, there are a few things that might happen which we are going to test and get a report.

“You have what we call insulation failure and ageing. Your insulation paper within a transformer, an oil degrade over time because of heat and moisture to a certain extent, resulting in oxidation.

“If you have those things within your transformer, it leads to what we call partial discharge, which may create an explosion.”

Ageing infrastructure remains one of the key risks facing the power utility. Insulation failure occurs when the internal insulating paper and oil inside a transformer deteriorate due to prolonged exposure to heat and moisture, leading to oxidation and, ultimately, partial discharge that can trigger an explosion, he said.

Mechanical issues

Another possible factor is mechanical issues within a transformer, which can cause internal faults. Oil degradation or contamination is another concern.

“The contamination of oil that you put with a transformer, as a result, the oil breakdown can cause heat, and that heatcan  cause combustion gas.” 

Operating beyond the rated current capacity, commonly referred to as overloading, may also result in transformer explosions. “There’s a certain capacity for example, that transformer that exploded is an 80 mVa transformer.

“In normal capacity you run 70% of that, but because of the ageing and what we experienced on Saturday evening, because a first electrical trip happened on Saturday in transformer one.”

Ageing infrastructure

“As a team we had a problem because the ageing infrastructure doesn’t only confide to the transformer, we have what we call associated equipment like breakers. One of breaker we found from 33 kVA in Bayswater had a problem, and that is why we opted to use transformer one that exploded Monday evening.

“There might be other factors, but these are the things that causes explosion, especially of transformers,” said Sekoboto.

The worst-case scenario for power cuts in such incidents is 72 hours, he said. This was avoided as Centlec committed to restoring power within 24 hours, a target that was successfully met.

Sekoboto also applauded the Mangaung fire and rescue department for its swift response to the fire on Monday, helping to contain the situation and prevent further damage.

Power supply

Centlec has been rolling out a programme to replace ageing infrastructure at various power stations, including the Bayswater distribution centre. As part of its contingency planning, the power utility is looking to link the Westdene power networks via Navalsig to the Bayswater distribution centre.

This would allow for the diversion of power supply should similar challenges occur in future, reducing the risk of prolonged outages across the city.

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OFM News/Kekeletso Mosebetsi dg