Low-maintenance option for SA’s ageing mini substations

Electrical Power & Protection

April 2022 Electrical Power & Protection

As South Africa’s many thousands of oil-cooled mini substations reach the end of their operating lives, there is scope to replace them with a safer and more economical option, according to Trafo Power Solutions’ managing director, David Claassen. “These mini substations are located all along our urban streets, in shopping centres and around industrial areas – in close proximity to growing numbers of people,” he said. “As municipalities struggle to maintain these properly, they pose an increasing safety risk and become more expensive to service and repair as they get older.”

A 500 kVA dry-type mini substation supplied by Trafo Power Solutions.

He pointed out that oil-cooled transformers require regular testing and maintenance, including monitoring and replacement of oil at regular intervals to ensure effective cooling of the unit. Without this maintenance, the risk of failure or even explosion is raised. “Dry-type transformers do not contain oil, being cooled by air moving over the components. This is one of the factors behind the significantly lower maintenance required by dry-type transformers, which of course translates into substantial cost savings over time,” said Claassen.

The absence of oil makes dry-type transformers considerably safer, he explains, as indicated by these units’ F1 fire rating. This means they are resistant to flammability, they are flame retardant and they generate no harmful emissions. Having no oil as a coolant also makes dry-type transformers less risky to the environment. Mitigating the risk of oil spilling from an oil-cooled transformer – which can lead to the contamination of land and water – requires the construction of a bund wall. The dry-type option needs little of this kind of additional infrastructure, and so is more cost-effective to install.

A 500 kVA dry-type mini substation being rigged into position at a commercial building site.

“Trafo Power Solutions has worked extensively with developers of high-traffic infrastructure like shopping centres, ensuring the highest level of safety in mini substations located in high-density areas,” Claassen continued. “We are well positioned to supply public utilities with the same benefits.” He further noted that municipalities’ financial resources for service and maintenance of substations are often severely stretched, so it makes sense for them to seek more economical alternatives. Dry-type transformers are almost maintenance-free, taking a considerable load off the owners’ maintenance duties.

“We custom-design our solutions for dry-type miniature substations to meet customers’ exacting requirements,” said Claassen. “This includes any variation of medium-voltage (MV) and low-voltage (LV) needs, and specific switchgear as well as customised control and protection options.”

Trafo Power Solutions supplies miniature substations from 200 kVA to 2500 kVA – ranging from 3,3 kV to 33 kV on the MV side, and from 400 V to 1000 V on the LV side. These substations are rated to the IP65 level of ingress protection.

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Low-maintenance option for SA’s ageing mini substations

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