Modular, mobile dry-type transformers ideal for Africa

25th August 2017 By: Robyn Wilkinson - Features Reporter

Modular, mobile  dry-type transformers ideal for Africa

SAFER OPTION Dry-type transformers are completely flame-retardant and emissions free, using resin and vacuum-pressure impregnation to insulate windings and air as a cooling agent

As mining projects move into ever- more remote locations in Africa, modular and mobile energy solutions – such as dry-type transformers – are gaining popularity, says transformer supplier Trafo Power Solutions MD David Claassen.

He explains that transformers – which increase or decrease voltage – consist of copper or aluminium windings that need to be insulated and cooled down. Historically, oil transformers have been the standard in the South African market, with oil proving a highly effective insulator and cooling agent.

However, Claassen notes that oil has also presented a safety risk, as a result of its high flammability, with transformers catching fire from either internal electrical faults or external influences. The use of oil, moreover, produces gas emissions.

In contrast, the dry-type transformers are completely flame-retardant and emissions free, using resin and vacuum-pressure impregnation to insulate the windings and air as a cooling agent. This makes the transformers ideal for mining applications in hazardous, highly flammable underground or surface mining environments, including metals, coal and oil and gas.

“In the past, dry-type transformers have typically been bigger and more expensive than their oil counterparts. But, this gap is starting to close, with dry-type transformers now available in similar sizes and at similar prices to their oil counterparts. The safety and environmental benefits of the dry-type transformer, thus, give it a clear competitive edge.”

Trafo Power Solutions imports dry-type transformers to South Africa from Canadian manufacturer Hammond Power Solutions’ (HPS) manufacturing facilities, in Italy.

The company undertakes the testing of the transformers destined for typical indoor applications, which arrive fully engineered, as well as additional engineering on transformers for outdoor applications. Additional engineering includes the manufacture of miniature substations, which require a housing structure, an incoming medium-voltage switchgear section and low-voltage distribution section. The completed transformers are then shipped to mine sites throughout Africa, reducing construction time and labour requirements on site. Special customer requirements can also be accommodated in the design and manufacture of the transformers in Italy.

“Dry-type transformers are easier to build and manage than their oil counterparts. They are also well suited to modular design, as they can be used indoors, while oil transformers must be built outdoors in a specialised bund that protects the ground from oil leaks – which is expensive and time-consuming,” notes Claassen.

He further points out that such transformers are structurally more robust than oil transformers and, thus, better suited to travelling over the uneven roads and steep inclines to mining locations in Africa, especially when oil leaks are a common problem among oil transformers. Trafo Power Solutions can, moreover, reinforce the core and structure of its dry-type transformers to further strengthen them for journeys over significantly rough terrain.

The sturdy design ensures meeting increasing demand from openpit and underground mines for mobile energy solutions that can be easily and safely moved, with equipment, to new locations as mining progresses.

Having observed an upward trend in the demand for dry-type transformers in the African mining industry, part of HPS’s business strategy has been to increase its presence on the continent.

“We have, thus, partnered with HPS to provide an on-the-ground team that is familiar with the African market and can support its products through offering technical assistance and a comprehensive range of after-sales services,” says Claassen.

The transformers comply with the European ecodesign directive, which delineates minimum standards for energy losses from transformers. This provides proof of the high efficiency of Trafo Power Solutions’ dry-type transformers, which provide a lower total cost of ownership than less efficient models, he adds.

“These minimum standards are not yet the norm in Africa, but we are seeing more demand for high-efficiency products and believe that our compliance with the European directive will ensure our clients that they are getting value for their money.”

In addition, end-users will benefit from the reduced energy consumption of these transformers, which is another factor that Claassen says has attracted attention to these units in new and existing markets. The higher efficiency of the cast resin design means lower electricity bills and reduced heat loss. These units, therefore, require only a minimal movement of air across the windings to cool them down, although forced air options can also be employed, where necessary, if ambient temperatures are high.

Dry-type transformers also require less maintenance and can last for 25 years without significant attention, while oil-filled transformers require regular maintenance, including oil sample analysis to ensure operational consistency and safety.

True Test of Strength
Trafo Power Solutions will deliver four dry-type transformers to a mine in Sierra Leone for large-scale mobile mining substations next month. The transformers have arrived in South Africa, where substations will be built before being shipped to site.

“Trafo Power Solutions is not simply a transformer distributor but also a solutions-based company. We endeavour to treat each project as unique and, in this case, we worked closely with the client to generate the right design for the effective cooling of the transformers and to ensure optimal overall performance,” says Claassen.

A key feature of the project is its capacity, with a primary voltage of 13.2 kV, a secondary voltage of 480 V and a frequency of 60 Hz, which is higher than the norm of a primary voltage of 11 kV and a secondary voltage of 400 V. The transformers will, moreover, have to withstand a road journey from the port, in Freetown, to site and will function as mobile units once there.