Twenty custom-designed transformers are being prepared by dry-type transformer specialists Trafo Power Solutions for a liquified natural gas (LNG) plant being constructed in northern Mozambique. 

The 20 transformers feature a specialised design that ensures high levels of ingress protection, according to David Claassen, managing director of Trafo Power Solutions. These units – ranging from 400 kVA to 1600 kVA – are housed in IP56 enclosures, for protection from fine dust and water. This solution has been achieved despite the transformers being cooled by air rather than oil.

“By applying world-class technology and expertise, these transformers are designed to operate reliably in humid and dusty outdoor conditions, providing continuous rated power without the use of any forced cooling,” Claassen says. 

The specialised design of the transformers accommodates elements such as temperature rise, losses and insulation systems – suiting each unit for the application and the load it will supply. 

“They will step down voltages from 6,600 V in the medium voltage (MV) network to 420 V required in the plant, and will supply various motor control centres,” he says. “Their specific designs will meet the requirements for various different impedances, voltages and K-factors for non-linear loading.”

This specialised solution is being supplied in a strategic partnership with Italian technology leader TMC Transformers. Together, the companies competed with the world’s leading OEMs for the prized contracts in this LNG mega-project – reportedly the largest-ever single foreign direct investment in Africa.

Trafo Power Solutions will also be supplying dry-type transformers for a Zone 2 hazardous area of the plant, requiring compliance with strict classifications and stringent sign-off from certified professionals. 

Claassen emphasises the safety advantages of dry-type transformers, which do not use oil as a coolant. They therefore pose no hazard in terms of fire, explosion or environmental damage. The transformers also need minimal maintenance, which an important benefit when located on such a remote site. 

While it might seem at first glance that there is little to distinguish one transformer from another in terms of design and construction (other than size), the differences can in fact be substantial and potential buyers need to be aware that there is certainly far more to a transformer than initially meets the eye.

David Claassen, managing director of Trafo Power Solutions, says that in order to make an informed decision as to which product will best meet the needs of a particular application, the customer will need to look at several factors, including the ambient temperature ranges in which the transformer will operate, the expected core and copper losses, the load conditions and the ability of the manufacturer to test products in accordance with appropriate standards.

“The minimum, maximum and average temperatures in which a transformer can safely operate will affect the design and consequently the price of a transformer,” he explains. 

In dry-type transformers, two main temperature winding insulation classes exist – namely Class F and Class H. Class F allows the transformer to operate safely at temperatures up to 155°C without damage while Class H allows the transformer to accommodate temperatures up to 180°C.

Claassen says another detail to look out for is that both oil-cooled and dry-type transformers are available in multiple cooling options. 

“The most common is natural air (AN), where the surrounding still air is used to keep the transformer operating within the correct temperature range. The second most common option is the forced air (AF) method, which entails moving air over the radiators, or over the core and windings. This allows the temperatures to be kept in check,” he explains. Transformers using forced cooling are able to supply additional load over and above the nominal power rating but it is important to rate the transformer at AN (natural ventilation) and use the fans as a temporary measure. 

With regard to transformer losses, these comprise two parts – load or core losses and no-load or copper losses. It is important to note that there are IEC standards set up as to what the maximum allowable load and no-load losses may be. The higher the transformers losses are, the cheaper it is to produce and the operational cost will be higher 

Also important is the load that the transformer will supply (or be supplied by). Unfortunately, with today’s modern grid there is no such thing as a perfect load. Power electronics, as well as many other switching electronics, have contributed to non-sinusoidal waveforms, and hence harmonics. The Total Harmonic Distortion (THD(i)) that a transformer encounters significantly influences the design of that transformer.

Finally, potential buyers need to look carefully at the quality control programmes manufacturers have in place. These will ensure that at all stages of manufacturing all raw materials and components can be tracked. 

Dry-type transformers supplied by specialist company Trafo Power Solutions are ensuring the safe and reliable operation of substations in a construction camp at a large liquified natural gas (LNG) project in northern Mozambique.

According to David Claassen, managing director of Trafo Power Solutions, 18 dry-type transformers were included in modular substations built in South Africa and shipped to site recently. The company is in a strategic partnership with leading Italian transformer manufacturer TMC Transformers, and is competing at the highest level with other global OEMs.

“These substations are for the project’s first construction camp of about 9,500 contractors,”  Claassen says. “Our transformers have been specially designed for the high ambient temperatures in northern Mozambique.”

Ranging from 500 kVA to 1250 kVA, the temperature of these units will rise to a maximum of only 80⁰C when under full load. With Class-H insulation on both the medium voltage (MV) and low voltage (LV) windings, they will withstand a temperature of 180⁰C. This is considerably more than the potential 40⁰C ambient temperature in the tropics plus the 80⁰C temperature rise. The transformers are also designed for levels of humidity up to 95%.

He highlights that the safety advantages of dry-type transformers allow them to be used in this application. As they do not contain oil – which is the usual coolant in conventional transformers – they pose no fire, explosion or environmental hazard. 

“A transformer containing oil would present a significant risk in a construction camp accommodating thousands of people in close proximity,” he says. “The safety level of dry-type transformers also means that they can be used in enclosed spaces like modular substations. The minimal maintenance required is an added advantage, being located on such a remote site.”

Claassen notes that the global competition to supply this mammoth project has been intense, and points to the vital partnership between the local knowledge and experience of Trafo Power Solutions, and the technology and expertise of TMC Transformers.

Dry-type transformer specialist Trafo Power Solutions is growing its footprint in mining and beyond with increased take-up of its safe and reliable technology.

“Our contract pipeline is a clear demonstration of the market’s confidence in dry-type transformers, especially for indoor applications, hazardous areas, remote locations and demanding outdoor environments,” says David Claassen, managing director of Trafo Power Solutions.

Recent orders have included a specialised 3900 kVA unit for a large coal mine in Limpopo province. With a primary voltage of 11 kV, this dry-type transformer delivers through four different secondaries of 1810 V, 1500 V, 1400 V and 1200 V. To operate reliably in the dusty outdoor location, it is installed in an IP54-rated enclosure and cooled using air to air heat exchangers

Even during the Covid-19 lockdown, supply from the company has continued. Two 2000 kVA dry-type transformers were installed in a modular substation for a diamond mine expansion in Sierra Leone.

Trafo Power Solutions also recently supplied Africa’s largest liquified natural gas (LNG) project, under construction in northern Mozambique. Eighteen dry-type transformers are already on site, inside modular substations for the project’s first construction camp of about 9,500 contractors. Also being supplied are 20 specialised dry-type transformers for the project’s gas plant.

“We have been active in many other industries too, such as telecommunications, health, food and beverages, and commercial buildings,” says Claassen. “Our strategic partnership with a leading global player, TMC Transformers in Italy, allows us to leverage world-class technology and expertise for application in Africa.”

He highlights Trafo Power Solutions’ responsiveness to specific customer requirements, and its experience in custom engineering solutions that are fit for purpose. Backing up these offerings is a flexible, 24/7 support service from technicians in South Africa, who are ready to provide interventions on site where necessary. The company also provides customers further access to the engineering expertise at TMC Transformers’ state-of-the-art design and manufacturing facilities.

The steady uptake of dry-type transformers in the African market is being driven by the range of advantages offered by this technology, argues David Claassen, managing director of dry-type transformer specialist Trafo Power Solutions.

“We have seen wider application of dry-type transformers in Africa, as they move from niche products to more universal use,” says Claassen. “The reasons are not hard to find, and include safety, reliability and low installation costs.”

A key differentiator is that the electrical core and coils in a dry-type unit are cooled by normal air ventilation. By contrast, liquid-filled transformers are cooled by oil, silicone or other liquid. The risk of this liquid spilling is one of the main factors behind the increased use of dry-type transformers. The latter has higher levels of safety and does not present an environmental hazard.

“This makes dry-type units more suitable for indoor use, and also for underground and marine applications,” he says. “At the same time, they are also resilient enough for hostile outdoor environments.”

To insulate the windings and protect them from dirt, moisture, corrosive fumes and conductive dust, special treatment techniques are applied. Depending on the application, one of three main types of insulation is used: open-wound, vacuum pressure impregnated (VPI) or cast coil.

Among their safety benefits is their low fire hazard, with their transformer insulation made up of epoxy resin and eco-friendly quartz powder, the winding is flame-retardant. This also means it will not generate toxic gases when arcing occurs. The cost implication is that costly fire extinguishing equipment is rendered unnecessary.

“When locations are remote, as they often are in African applications, the installation of dry-type transformers makes good sense,” Claassen says. “This is because they are reliable and need little maintenance, while being easier and more economical to install.”

Without the risk of oil spillage, no concrete bund wall or significant civils works is required – saving time and money. Using only air for cooling, liquid testing is not required. At the same time, the smooth coil surface eliminates the build-up of heavy dirt. Designed to meet Class E2 environmental requirements, the units resist condensation and heavy pollution.

“In terms of high reliability, cast resin transformers typically have a service life of over 25 years and the failure rate has been shown to be very low,” concludes Claassen.

When a specialised dry type reactor failed after many years of service in a major banking company’s backup power generating system, Trafo Power Solutions was there to leverage its expertise and applications knowledge.

Trafo Power Solutions supplied and assisted with the installation of a replacement reactor, providing a fit-for-purpose design that accommodated the limited space and awkward position in which the components had to fit.

“The reactor – or inductor – is a key part of the bank’s backup system that feeds a number of buildings in the central business district of Johannesburg,” says Aaron Rost, contracts and proposals engineer at Trafo Power Solutions. “This vital component serves as a link between the utility power, the backup generator and the buildings’ supply.”

Rost explains that the reactor is important for a number of reasons. Among the most important are reducing the bank’s electricity costs, raising the system’s efficiency and contributing to the stability of the municipal power grid.

With its vast data centres, the bank must constantly idle its standby generators online, so that the switchover between utility power and standby power is seamless in the event of a power failure. He notes that to make better use of the fuel consumed by this continuous operation, diesel generators can be repurposed to help alleviate the data centre’s reactive power requirements.

“While active power refers to that element of the power supply that actually does the work – such as driving motors or powering lights – the reactive power is essentially useless power that is being wasted,” he says. “This reactive power effectively draws more current from a grid than what is really required.”

Rost highlights that the reactor stops any of this reactive power from being used from the power grid, This reactor also allows only the active power to be supplied from the grid, and in so doing helps create a more efficient system.

The importance of the reactor’s role in this power system is two-fold, he argues. Firstly, it reduces the bank’s electricity bill, as local municipalities charge a premium rate for the reactive power consumed.

“The reactive power raises the tariff that the client ends up paying at the end of the day,” he says. “By preventing the use of reactive power by the grid, the reactor allows the client to save directly on their overall energy costs.”

The second contribution that the reactor makes is that the local municipality does not have to deal with a ‘troublesome’ load, as this type of loading increases the amount of current being drawn.

“This then leads to additional heating in cables, transformers and switchgear, which erodes the life span of this equipment and can potentially lead to premature failure,” he says. “On a grid which is currently in a fragile state, any failed equipment can have massive implications for the equipment that is attached.”

Rost points out that the reactor also serves as a voltage regulator and filter on the utility power being supplied, allowing a more stable power supply to the building. This delivers a further benefit – in the event of a fault, the reactor can help to limit the fault current, making it less likely that costly utility equipment will be damaged.

When a specialised dry type reactor failed after many years of service in a major banking company’s backup power generating system, Trafo Power Solutions was there to leverage its expertise and applications knowledge.

Trafo Power Solutions supplied and assisted with the installation of a replacement reactor, providing a fit-for-purpose design that accommodated the limited space and awkward position in which the components had to fit.

“The reactor – or inductor – is a key part of the bank’s backup system that feeds a number of buildings in the central business district of Johannesburg,” says Aaron Rost, contracts and proposals engineer at Trafo Power Solutions. “This vital component serves as a link between the utility power, the backup generator and the buildings’ supply.”

Rost explains that the reactor is important for a number of reasons. Among the most important are reducing the bank’s electricity costs, raising the system’s efficiency and contributing to the stability of the municipal power grid.

With its vast data centres, the bank must constantly idle its standby generators online, so that the switchover between utility power and standby power is seamless in the event of a power failure. He notes that to make better use of the fuel consumed by this continuous operation, diesel generators can be repurposed to help alleviate the data centre’s reactive power requirements.

“While active power refers to that element of the power supply that actually does the work – such as driving motors or powering lights – the reactive power is essentially useless power that is being wasted,” he says. “This reactive power effectively draws more current from a grid than what is really required.”

Rost highlights that the reactor stops any of this reactive power from being used from the power grid, This reactor also allows only the active power to be supplied from the grid, and in so doing helps create a more efficient system.

The importance of the reactor’s role in this power system is two-fold, he argues. Firstly, it reduces the bank’s electricity bill, as local municipalities charge a premium rate for the reactive power consumed.

“The reactive power raises the tariff that the client ends up paying at the end of the day,” he says. “By preventing the use of reactive power by the grid, the reactor allows the client to save directly on their overall energy costs.”

The second contribution that the reactor makes is that the local municipality does not have to deal with a ‘troublesome’ load, as this type of loading increases the amount of current being drawn.

“This then leads to additional heating in cables, transformers and switchgear, which erodes the life span of this equipment and can potentially lead to premature failure,” he says. “On a grid which is currently in a fragile state, any failed equipment can have massive implications for the equipment that is attached.”

Rost points out that the reactor also serves as a voltage regulator and filter on the utility power being supplied, allowing a more stable power supply to the building. This delivers a further benefit – in the event of a fault, the reactor can help to limit the fault current, making it less likely that costly utility equipment will be damaged.

Underground mines in southern, central, and west Africa have been seeing the safety benefits of dry-type transformers from Johannesburg-based Trafo Power Solutions.

According to Trafo Power Solutions managing director David Claassen, this clientele even includes collieries, where the strictest safety regulations apply with regard to fire hazards.

“The high risk of fire in underground coal mining environments has led to a high demand for dry-type transformers,” says Claassen. “Among the fire risks that coal mines face are transformer short-circuits as well as fires reaching the transformer.”

He notes that dry-type transformer technology is rated Class F1 in terms of fire protection, ensuring that transformers supplied by Trafo Power Solutions are flame-retardant.

“Oil-cooled transformers, on the other hand, are a fire risk due to the oil they contain to cool the windings,” he says. “The risk is heightened by the harsh operating conditions in which many transformers must function on mines.”

These transformers also require regular attention and maintenance. Oil samples must be taken at prescribed intervals, and these must be tested at a laboratory with the appropriate accreditation. Testing must be conducted to ensure that oil purity is within bounds, and to check for gas levels and pressure build-up in the oil tank.

“This maintenance can present challenges and added costs if the equipment is located on a remote mine far from a source of expertise and the right equipment,” says Claassen. “With dry-type transformers, it is really only the temperature that requires monitoring. The equipment comprises limited componentry, so generally requires servicing only twice a year.”

He highlights that these regular inspections are brief and simple, taking just a couple of hours. Key aspects to be checked are the physical termination connections – which must be tightened to the right torque – and any dust that has gathered around the core and windings must be cleaned away.

Trafo Power Solutions has in recent years supplied dry-type transformers – along with ancillary power equipment such as low and medium voltage switchgear – to mines in South Africa, Mozambique, Zambia, the Democratic Republic of Congo (DRC), Ghana and Sierra Leone. In addition to coal, there are gold and base metal producers included in this clientele.

A focus on application engineering allows Trafo Power Solutions to supply customised dry-type transformers for a range of sectors including renewable energy.

“We begin at the proposal stage by engaging closely with the customer about the exact application and electrical load,” says David Claassen, managing director of Trafo Power Solutions. “This means that every project gets its own transformer design, so that it is fit for purpose.”

In the case of renewable energy applications, for example, there are some very specific demands that need to be accommodated. A solar power generating plant presents a situation in which a transformer will be energised from zero to 100% on a daily basis.

“This leads to wide fluctuations in temperature inside the transformer which, in turn, causes the resin around the windings to expand and contract considerably,” says Claassen. The windings in dry-type transformers are insulated in a cast resin or epoxy material, rather than oil, and rely on air movement for cooling.

“Such fluctuations could result in the resin cracking, so the design must specify the appropriate class of insulation to cope with these conditions,” he says. “We can design our windings for either a Class F or a Class H insulation. In addition,  the mixture of the resin is specially formulated to accommodate the duty cycle specific to renewable energy applications.”

The standard design – using Class F – can deal with temperatures up to 155 degrees Celsius. For many of Trafo Power Solutions’ low voltage and high voltage installations around Africa, the design includes a resin mix to Class H specifications. This gives it the capacity to withstand temperatures of up to 180 degrees Celsius.

Another aspect that needs to be considered for renewable energy applications is the non-linear load that inverters add to the mix. The transformers need to be designed with a K-Factor much higher than used for standard distribution type loads as well as the addition of an electrostatic shield between the primary and secondary windings, to eliminate potentially damaging leakage currents.  

Claassen notes that dry-type transformers are being increasingly specified for demanding applications such as renewable energy plants, instead of conventional oil transformers.

“With an oil-cooled unit, the temperature fluctuation arising from these rapid and regular energising and de-energising cycles brings its own challenges,” he says. “In particular, it causes more gases to be emitted within the transformer tank, which leads to a variety of problems.”

The cast resin material used in Trafo’s dry-type transformers meets the specifications of the International Electrotechnical Commission (IEC) for fire class F1. The units therefore present minimal fire risk, allowing them to be used indoors safely, and without environmental protection like bund walls for potential oil spills.

Claassen says dry-type distribution transformers are fast becoming a more suitable alternative to oil transformers, especially in the distribution power range between 50 kVA size and 10 MVA, although Trafo Power Solutions is able to supply dry type transformers up to a power rating of 25MVA

Transnet’s upgrade of its port facility at Saldanha Bay will include dry-type transformers from specialist company Trafo Power Solutions.

The company is supplying specialised transformers for the Tippler 3 project at the iron ore load-out station. Factory-acceptance testing was completed in December 2019, according to Trafo Power Solutions managing director David Claassen. Delivery to site is scheduled for February 2020.

The construction of a third tippler at the Saldanha Bay port is to sustain iron ore export volumes of 60 million tons per year when the existing tipplers are refurbished in future. It will integrate with the rail system bringing ore via the 860 km line from mines in the Northern Cape. Key aspects of the new infrastructure comprise the 285 tonne tippler itself, a loading vault below ground and a conveyor tunnel. New buildings, service roads, bridges, railway lines, conveyors, lighting and bulk electrical supply infrastructure are also part of Transnet’s upgrade project.

Trafo Power Solutions’ contract was for the design, supply and commissioning of five dry-type transformers. There are two 1000 kVA units and a 3150 kVA unit, both stepping down from 11 kV to 400 V. The other two units are 3500 kVA and 4500 kVA capacity respectively, taking 11 kV to 3,3 kV.

To resist the corrosive sea air, all the transformer enclosures will be manufactured from 3CR12 grade of stainless steel. The enclosures are also to be IP33-rated to ensure a high level of ingress protection against moisture and dust.

“The enclosure design also incorporates cable boxes and Type C, totally enclosed plug-in bushings for the terminations,” he says. “This provides a boot covering which is touch-potential safe, and also provides for efficient plug-and-play installation.”

This is a significant improvement on the regular lug and bolt copper connection, which would just be shrouded by a heat-shrunk material. The special terminations also facilitate easier maintenance or removal.

“The units will provide the medium-voltage supply for the Tippler 3 project and its associated infrastructure, including equipment like conveyors,” he says. “All the transformers will be supplying non-linear load to a certain extent, so they have been designed with a K-factor of four.”

The K-factor is a measure of a transformer’s ability to withstand the heating effects of non-sinusoidal harmonic currents created by electronic equipment. The higher the K-factor, the greater the harmonic heating effects.

As dry-type transformers are cooled without the use of oil, these units will receive forced ventilation when a preset temperature is reached. This ventilation is provided from a row of fans which Trafo Power Solutions has designed to be bolted below the location of the transformers.

Designed locally by Trafo Power Solutions, these dry-type transformers are manufactured in Italy by strategic partners TMC Transformers, experts in cast resin transformer technology. All products are routinely factory-tested according to IEC standards, but type-testing and special testing can also be conducted.

“The standard applicable to dry-type power transformers is IEC 60076-11,” Claassen says. “TMC’s advanced laboratory facilities allow us to conduct the full range of tests in-house, in accordance with what these standards and whatever other requirements are designated by the customer.”

At Saldanha, Trafo Power Solutions is also responsible for building auxiliary protection and control panels, which it locates remotely from the transformers. These include temperature control sensors that communicate with the port’s broader control and monitoring network.