Sebenza – biggest substation in SA in 10 years

September 2017 – This article has been published in Energize September 2017 issue. Click here to view the article on the EE Publishers website


Nearing its final months of completion, the Sebenza 400/275/88kV substation constructed and project managed by Consolidated Power Projects (CONCO) for City Power, will be the biggest substation to be built in South Africa in the past ten years. It will also be one of the main intake substations in the north eastern region of Johannesburg making it one of the country’s hubs that is set to stimulate much needed economic growth. It has been built with expansion in mind and is intended to increase in capacity from 315MVA to 1000MVA. This will dramatically improve reliability and stability of the grid.CONCO’s senior project manager, Thamie Nyembe, says, “We planned this project in three phases: phase one encompassed design/engineering, land development and civils with a massive 40 000m3 being allocated for the earthworks and 1700m3 for concrete with over 200 foundation structures built; phase two was machinery procurement and delivery including erecting of equipment; and phase three which we are currently busy with, entails the connecting and commissioning of the equipment and energizing of the substation. Basically, we are on track and expect initial energizing of the substation to take place in early December this year. This milestone is also dependent on ESKOM completing their work at Prospect Substation and energizing the lines to Kelvin at 275kV (presently energized at 88kV).

2271 “Depending on City Power’s ability to give us “shutdowns” without affecting consumers unnecessarily, we would be able to start swinging certain circuits from Kelvin Substation into the new Sebenza GIS switchboard. There is a total of 18 circuits to be swung over and due to certain constraints this will only be completed during the first quarter of 2018. However as soon as we start swinging circuits, this will start relieving the load off the aged Kelvin power station and Prospect substation plus enabling City Power to begin reaping benefit from the increased capacity,” says Nyembe.

Part of the Sebenza project involved CONCO having to upgrade and make additions to both Prospect and Kelvin substations which included installing four sets of reactors and new switchgear on some of the main feeders at Kelvin. Two of the Kelvin bays have been completed with the balance only becoming available once the Sebenza substation is energized.

The three enormous 3 x 315 MVA 276/88/22kV power transformers manufactured in South Africa by Actom are in the process of being delivered and tested on site. Unit one is complete and ready for commissioning, with unit two currently being installed. Unit three is expected on site by the first week of October and should be ready for commissioning by the end of October. Getting these transformers to site is a major operation whereby a 114 wheel truck is necessary to carry merely one transformer. Installing them is also a delicate process as they weigh in the region of 100+ tons each.

2218The impressive three-story GIS building houses the latest technology equipment. Protection and control systems have been designed, engineered and manufactured by CONCO Energy Solutions and state-of-the-art Gas Insulated Switchgear (GIS) has been designed and manufactured by ABB. The 132kV GIS board comprising 38 bays is the largest such high voltage board ABB has supplied in Africa. The SCADA systems have been developed and installed by CONCO Energy Solutions to enable remote monitoring and control by City Power.

“Due to the sheer magnitude of this project, management of it is significantly challenging hence the need for meticulous project management and continuous support from our consultants PSW, City Power personnel, CONCO’s site-based management and our sub-contractors,” expressed Nyembe.

Contact: Thamie Nyembe on +27 11 805 4281 or email