Buoyed by rising commodity prices, mines in Africa will soon be reinvesting in expanded, safer and more efficient energy infrastructure; and dry-type transformer technology is an increasingly popular choice says Trafo Power Solutions MD David Classen.

This article first appeared in Mining Review Africa Issue 4 2018. 

“Installed in a range of applications and climates, dry-type transformers have also proved themselves in the compact spaces of mini substations, which Trafo Power Solutions is now able to custom-design for Africa’s mining sector,” says Claassen.

The company leverages more than a century of experience from industry pioneer Hammond Power Solutions (HPS), which has leading transformer design and manufacturing facilities in Canada, US, Mexico, Italy and India.

As the largest producer of dry-type transformers in the world, HPS also draws on world class expertise of subsidiaries such as Marnate in Italy, global front-runners in cast resin technology.

“This allows us to source high quality transformers from Italy, designed and manufactured to our specifications according to what the customer needs,” he says.

“Customising these transformers for our mini substation designs allows Trafo Power Solutions to offer mines around Africa considerable operational and cost benefits.”

While mini substations have traditionally been built with oil-cooled transformers, the dry-type option offers higher levels of safety as there is less fire risk due to the absence of oil as a coolant.

“This makes the dry-type mini substations a good option for underground mines, as they do not pose a fire or explosion hazard,” he says. “Mini substations are also a regular feature in many public spaces, as they are so widely employed wherever there is economic activity. The dry-type transformer enhances public safety in these applications.”

Claassen highlights the general growth in demand for dry-type mini substations in mining, pointing out that a number of major mining companies have standardised on the use of dry-type mini substations in underground operations. Some, he says, have even extended this requirement to their surface mines.

“It is clear that mining companies globally are pursuing every opportunity to create a safer environment for their mining operations, and the increasing price parity between dry-type and oil-cooled technologies means that there is now every reason for mines to consider the dry type option,” he says.

There is also lower risk of environmental contamination, so the customer saves on the cost of civil infrastructure such as bund walls around the substation facility.

Lower maintenance requirements of dry-type substations also have a positive impact on costs, especially when the units are located in remote areas – a common characteristic of mining operations – which are time consuming and expensive for service technicians to reach.

“The confined spaces inside mini substations make transformer maintenance much more challenging than working in a larger unit,” he says.

“Even finding and fixing a relatively small problem like an oil leak may necessitate moving the whole unit off site for repairing in a workshop. The absence of oil in the dry-type substation significantly reduces the level of maintenance and disruption.”

Trafo Power Solutions offers mini substation design and manufacture in a range of capacities and for different applications.

“We design the enclosure to suit the customer’s available dimensions, sourcing and installing medium voltage and low voltage switchgear according to their brand preference,” he says.

The company can design and supply mini substations in a capacity range from 315 kVA up to 1 000 kVA, with a variety of voltages from 3,3 kV up to 11 kV on the medium voltage side and from 400 V to 1 000 V on the low voltage side.

The enclosure may be required to be particularly rugged to accommodate movement and vibration, in which case a thicker steel can be specified.

The units can also be designed for mobility, with options of wheeled or skid-mounted bases.

He emphasises that a key aspect of the design must to be facilitate the flow of air to cool the transformer, while still ensuring that the enclosure protects the components from the outside dust and moisture, especially since the mini substations are usually placed in the open.

“This requires a detailed heat flow analysis, where we conduct a study of air flow across the transformer,” says Claassen. “Our resultant aerodynamic design – together with a specialised dual fan system – then ensures that cool air can be introduced in sufficient quantities into the mini substation’s enclosure, efficiently dispelling the warm air to dissipate the heat generated.”

The design must also minimise the amount of heat in the enclosure, and a key advance here is in the improved efficiency of the transformer, resulting in reduced energy loss. This better efficiency also means lower energy costs and higher levels of reliability.

“With its experience and expertise, HPS has developed dry-type transformers that are well suited to applications in confined spaces,” he says. “This is well proven in the maritime sector, where its dry-type mini substations are frequently installed in marine vessels with limited space.”

He emphasises that a transformer is a critical item on most mining sites, with a direct impact on mine production levels and profitability.

“This means that mines want to deal with a supplier who has a proven and quality product, with the expertise and references to ensure smooth and reliable operation,” says Claassen. “The partnership of Trafo and HPS provides this.”

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