State-owned power utility Eskom has ordered a set of five trailer-mounted substations from electrical solutions company Zest WEG Group to assist with substation uptime.

The mobile substations are mounted on a specially designed, five-axle low-bed trailer and feature a transformer and associated incoming and outgoing switchgear.

Zest WEG Group energy systems director Gary Daines tells Engineering News that, to date, the company has built and delivered a 10 MVA, a 20 MVA and a 40 MVA unit to meet Eskom’s key substation requirements. Delivery took place between September 2014 and March 2015.

Eskom has subsequently ordered another two 20 MVA units, which Zest WEG Group is manufacturing.

Daines says the contract for the first three units is valued at R70-million, while the additional two units are worth R45-million.

“These mobile units are specifically designed for Eskom and are used during substation maintenance when an existing substation is bypassed while repairs are being done.”

He explains that, during the design phase of the substations, Zest WEG Group prioritised not only mobility but also the weight of the units, which required adaptations to suit low-bed trailers. The 40 MVA unit, for instance, employs a dual dolly-axle configuration in front to assist in bearing the load, as well as steerable rear axles to assist in manoeuvring the unit in confined spaces. The low-bed aspect was incorporated to cater for the height restrictions at most substation premises.

The transformer and switchgear were also adapted to accommodate continuous movement induced through haulage.

Daines explains that the company leveraged the technology used to develop these substations from its Brazil-based parent company WEG, which pioneered the technology for the Brazilian industry.

Zest WEG Group will showcase its mobile substations at Eskom Park, in eMalahleni, on April 23, where Eskom representatives will provide technical demonstrations.

Local Transformer Factory Expansion
Zest WEG Group plans to increase production output of transformers from its local facility in Wadeville, Gauteng, to expand its capability and capacity to supply the domestic market and increase its footprint in Africa.

The Wadeville facility is the former factory of British electrical switchgear manufacturer Hawker Siddeley, which Zest WEG acquired in September 2013. The company has spent R130-million in capital investment on upgrading the facility.

To date, WEG Transformers Africa, the transformer branch of the Zest WEG Group, has supplied more than 350 transformers to Eskom, ranging from 5 MVA to 160 MVA and up to 132 kV.

Noteworthy orders were received subsequent to Eskom’s 2007 overhaul of its transmission network. “These orders really helped establish our business in the transformer segment,” says Daines.

He adds that Zest WEG Group is well established in the mining and power utility sectors across Africa, including Namibia, the Democratic Republic of Congo, Ghana and Mozambique.

“With our presence, WEG saw the opportunity to increase its manufacturing base in South Africa, with the transformer facility adopting a parallel approach to manufacturing with the development of new technologies and implementation of new manufacturing processes.”

The WEG Transformer Africa facility focuses on inverter transformers, which are used in conjunction with WEG variable-speed drives.

Currently, this facility manufactures transformers of up to 10 MVA at 33 kV, with the intention of increasing manufacturing capability to 40 MVA in the near future.

Daines says the transformers manufactured at the WEG Transformers Africa facility are “Africanised” to ensure that they are able to endure the harsh conditions and often “treacherous” haulage from South Africa to North African countries. This involves rein-forcing certain components using bracing and supports.

Gas-Generation Market Potential
Zest WEG Group is focusing on gas-powered electricity generation in industries where methane is prevalent.

Zest WEG Group installed a gas-powered generator in October 2012 at water utility Johannesburg Water’s Northern Wastewater Treatment Works.

The generator is powered by an engine manufactured by Spanish gas-engine manufacturer Guascor. This engine is, in turn, powered by purified methane gas extracted through the anaerobic digestion of sludge.

“The gas generator enables the wastewater treatment works to exploit gas produced as part of the plant process, ” notes Daines.

The generator produces 1 MW, which is used to supplement the plant’s electricity consumption. He notes, however, that, with additional enhancement to the wastewater treatment works’ digesters, the plant can produce enough power to satisfy all the requirements.

Daines says, although gas-powered electric generator solutions “are rapidly gaining traction in the local and international market”, gas generators still represent only a small segment of the generator industry.