Eskom is preparing to introduce 11 synchronous condensers – seven new and four repurposed – across its transmission system to support grid stability as the penetration of variable renewable-energy generators rises.

The need for the synchronous condensers – to provide dynamic voltage support, inertia and short-circuit current required for the integration of inverter-based technologies – was identified in a recent power system modelling study conducted by the State-owned company.

The study indicated that the first seven synchronous condensers would be required by 2027.

Eskom Transmission MD Segomoco Scheppers reports that various sizes of synchronous condensers will be introduced at different nodes across the transmission grid, including two apiece at the Camden and Grootvlei power stations, where generators will be repurposed to perform synchronous-condenser functions when the stations are decommissioned.

Eskom tells Engineering News that the seven new synchronous condensers are planned for installation at, or near to, the existing substations of Aggeneis, Gromis, Gamma, Koruson, Grassridge, and two at Ferrum.

The study also indicated the need for synchronous-condenser functionality in the vicinity of the Avon open-cycle gas turbine plant, in KwaZulu-Natal.

“Following power system analysis and simulation studies performed on the transmission network, based on our assumptions on renewable energy integration and the projected decommissioning plans for some of the baseload synchronous power stations (as indicated in the IRP 2019), the locations and sizes of the synchronous condensers were determined,” Eskom tells Engineering News.

“The location of the synchronous condensers also confirms that they are required to support the network in areas with high renewable-energy penetrations.”

No final capital investment figure has been provided, but Eskom expects the cost  associated with repurposing generators at Camden and Grootvlei to be lower than the purchase of new machines, which are synchronous motors where the shaft is not connected to anything and spins freely.

Conversion costs are estimated at between $20 000/MVAr and $50 000/MVAr, while the cost of new synchronous condensers is expected to be at least double that level.

“We will follow our Eskom procurement process to appoint an EPC contractor to design, construct and commission the infrastructure and hand-over to Eskom Transmission for operations and maintenance,” Eskom confirms.