Strong grid-connection demand from renewable project developers

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South African power utility Eskom has received 156 applications and requests for grid connection from renewable energy power project developers, representing a combined potential generating capacity of 15 154 MW.


Of that total, 13 252 MW were wind energy applications, Eskom network planning chief engineer Riaan Smit reported on Tuesday.


He added that these applications, or requests for indicative costs of embedded generation, would be formally processed once the renewable-energy feed-in-tariff (Refit) programme requirements were fully available.


Refit requirements were eagerly awaited by the renewable energy industry, and were said to be under final discussion by the Department of Energy, the National Energy Regulator of South Africa (Nersa) and the National Treasury. On conclusion, the process would move ahead.


The indicative costs for grid connection required detailed technical work, but would be required for projects seeking a power purchase agreement. A connection, and use of system agreement would also have to be signed.


The Eskom network planning division was busy with building transmission and distribution in-house network capacity, and conducting fault studies. These would be used in feedback to developers to assist with applications. Planning procedures were also being developed and tested within Eskom.


The applications received to date showed that renewable energy development areas, for example solar in the Northern Cape, would require numerous extra 500 MVA substations over the long-term, and additional transformer capacity would be required in order to feed this renewable electricity into the grid.


A three-year lead time would also need to be given, so as to ensure environmental impact assessments and technical studies could be completed.


Funding for shared networks would also need approval from Nersa.


Smit also highlighted a number of technical concerns with grid connection, including: the thermal loading of lines or transformers, voltage variations during normal operation, voltage recovery after faults, voltage sags owing to breaker operation, reactive power control, cable or transformer inrush currents, short circuit currents, impacts on power quality aspects, influence on ripple control systems, limiting system losses, and transmission system requirements such as stability and subresonance.


He said that technical studies and analysis would need to be done to ensure acceptance. But also noted that many of these issues were not applicable to wind power generation.
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