Custom Engineered Mobile Distribution Switching Stations Extend

The Zest WEG Group has extended its market reach into a new arena with the successful handover to Eskom’s Central Region of four 22 kV/11 kV unique mobile distribution switching stations, conceptualised and manufactured by Zest Energy, a Zest WEG Group company. These one-of-a-kind fully integrated units were engineered to suit specific Eskom requirements including the ability to be used in different configurations.

The mobile distribution switching stations can be rapidly deployed to a site and quickly connected to support substation maintenance or emergency circumstances, improving the availability of Eskom’s electrical network. These units were also manufactured in accordance with South African road ordinance requirements to eliminate the need for special transportation permits.

“Zest Energy is involved in different types of substation and reticulation project work including fixed type conventional outdoor substations (typically up to 275 kV) as well as mobile substation solutions with a variety of configurations and voltages to meet different customer needs,” Alastair Gerrard, Zest Energy projects manager, says.

“Although the Zest WEG Group has been supplying transformers to Eskom on contract for several years, this is the first time that the group, through Zest Energy, has been tasked with innovating and developing an engineered solution of this type. Working closely with the Eskom project team, we developed this design from scratch to ensure that it met Eskom’s standards and specifications. The only off-the-shelf component in the entire mobile switching station is the MV switchboard.

“Part of the integrated solution is that all protection systems are on-board, as well as all supporting systems, to enable the operation of switchgear in a safe and controlled environment. This is essentially a fully-fledged switching station on wheels that runs on external auxiliary power supplied by the customer. There are other versions of mobile switching stations which involve putting switchgear into standard marine shipping containers and transporting them to site, but this product is a truly mobile solution that can easily be moved to site as, and when the need, arises.

“Having proved that we have the in-house capability to develop mobile solutions of various forms designed to meet different customer specifications, we continue to see new market opportunities opening up whereby we can provide other industrial sectors with custom engineered mobile solutions.”

Each mobile distribution switching station comprises two compartments, a medium voltage (MV) switchgear compartment and a switching control compartment, separated by an internal wall. Both compartments can be accessed directly from the outside of the trailer through fold-down single lever operated doors with fully incorporated handrails and steps. There are also sliding doors behind each main door to facilitate safe use of the switching station during extreme weather conditions.

Sollie Herbst, Zest Energy electrical design engineer, adds that safety was a very big factor during the design phase.

“Despite the space constraints associated with such a solution, all safety aspects were taken into account and catered for to the highest standards,” he says. “For instance, the unit is fully controllable from a mimic panel in the switching control compartment of the trailer, effectively removing the operator from the vicinity of the breakers in the MV compartment during switching.”

Each mobile distribution switching station’s enclosure is custom built and integrated with a bi-axle, step-deck trailer which is, in turn, equipped with air suspension and ABS brakes. Each switching station incorporates an 11 panel, fixed pattern type MV switchboard (22 kV, 1 200 A, 25 kA/ 3s, 50 Hz) modified to accommodate standard Eskom protection schemes on board. The system is also integrated with other standard Eskom auxiliary systems, including metering, AC/DC power supply, BTU system with batteries and communication. Cable entry is designed as bottom entry through special access doors in the floor of each trailer and each cable can easily be terminated to the MV breaker terminals.

The switching stations can also be used in coastal or polluted regions, owing to their double-insulated enclosure walls and roof as well as the non-corrosive materials of construction.

The Zest Energy team offers extensive expertise in the power generation and energy industry. Whether a single solution or a combination of power generation solutions is required, Zest Energy’s services include the supply, manufacture, erection and maintenance of power generation equipment ranging from complete power plants and co-generation systems to custom engineered power generation and integrated energy solutions for new or existing mining and industrial companies.

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