Dry type transformers the preferred choice for African mining

For a long time brick and mortar substations that made use of oil transformers were the de facto standard at African mines.

Now, as companies intensify their efforts to exploit mineral potential in more remote areas on the continent, miners are turning to mobile power solutions that make use of dry type transformers in substations.

DAVID CLAASSEN, MD of Trafo Power Solutions (Trafo) explains to GERARD PETER why dry type transformers are cost-effective and more importantly, safer to use in mining operations.

This article first appeared in Mining Review Africa Issue 5, 2020 Read the full digimag here or subscribe to receive a print copy here

Founded in 2017, Trafo is a leading supplier of transformers to mining operations throughout the African region, including Zambia, the Democratic Republic of Congo (DRC), Mozambique, Sierra Leone and Ghana.

The company's clientele varies from Greenfields projects to upgrades at existing operations across a variety of commodities including gold, coal, tin and base metals.

Collectively, The Trafo Power Solutions team has nearly 20 years’ experience of supplying turnkey power solutions to the mining industry.

Trafo's main focus is on the supply of dry type transformers and associated power equipment such as low and medium voltage switchgear.

According to Claassen, there are a host of different applications for these transformers – anything from standard-type designs for indoor use to complex substations at underground mines.

In simple terms, oil-based transformers make use of oil in order to keep the parts of the transformer, such as windings and the core, insulated.

However, it poses a major fire risk, particularly in harsh operating conditions. On the other hand, dry type transformers only use air to cool the transformers.

Dry transformers are also well suited for harsh conditions such as underground coal mining operations.

"Firstly, there is a high demand for dry type transformers in coal mining because there is a high risk of fire in this type of operation," explains Claassen.

"Dry transformers are rated for Class F1 fire protection. Generally, speaking if you look at the benefits over oil transformers, they are mainly around safety from a fire hazard perspective – this could be a fire caused by a transformer short circuit or a fire reaching the transformer. In both types of scenarios, our transformers are flame retardant, whereas oil transformers are a fire risk," he adds.

A new trend emerging

For many years, dry transformers cost significantly more than their traditional oil counterparts. However, this has now changed with the cost for either transformer being on similar lines.

Furthermore, when it comes to operational costs, dry transformers are more cost-effective. "In terms of maintenance, oil transformers are very maintenance intensive," Claassen states.

"You need to take oil samples that need to be tested at an accredited lab. This can be a logistical nightmare if a mine is in a remote area. You also need to check for leaks, measure oil temperature, monitor gas levels and check to ensure that there is no high pressure build up in the oil tank, all of which take up a lot time.

"When it comes to dry transformers, you only have to monitor the temperature. Also, because dry transformers have few parts, they only need to be serviced once every six months.

"All you need to do is check all that all the physical termination connections are tightened to the correct torque and remove any dust build up around the core and the windings. All of this takes a maximum of two hours to complete."

Offering further peace of mind

As stated earlier, the trend of building solid foundation substations in Africa is slowly dissipating. This is largely due to the fact that it is costly to get building materials to remote locations as well as have manpower on site to build these structures.

"Nowadays, a lot of substations are being built in modular structures such as sea containers. In fact, at Trafo we can assemble an entire substation in South Africa and ship it to its location where there is very little cabling needed to install it once it reaches there," adds Claassen.

To ensure that its offering meets the unique requirements of each of its clients, Trafo invests heavily in application engineering upfront. In fact, the company hardly ever supplies the same transformer to different operations as each operation has its own environmental requirements and voltage supply requirements in different regions of Africa.

While dry transformers are relatively hassle free when it comes to service and maintenance, Trafo also offers its customers aftersales support from its head office in South Africa for additional peace of mind.

"We like to plan for any eventually. Our focus upfront minimises the risk but we also offer service agreements for maintenance. In addition to telephonic technical support, we offer on-the-ground service within three days of being notified in the sub-Saharan region," he concludes.

Did you know?

Trafo Power Solutions has an engineering database of over 1 million designs and solutions, ranging from the smallest of control transformers to the largest dry-type transformers available today.