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Eskom is in the process of strengthening the transmission corridor between the North and South of South Africa by constructing a new 765 kV backbone to meet the challenge of increased electricity demand. Eskom's existing substation layouts are based on double busbar arrangements. The approved new extra high voltage (EHV) substations (765 kV and 400 kV) will be based on a breaker-and-a-half substation design. Associated with this upgrade, new generation protective relay schemes for transmission lines (both line impedance and line differential), transformers, reactors and busbars will be implemented. The paper gives an overview of the new substation layout as well as the protective relay scheme architecture. The advantages of using the IEC61850 based protocol between the bay and substation control as well as GOOSE messaging for control of the breaker-and-a-half schemes will be discussed. The paper also describes the test philosophy and how GOOSE messages have been configured to improve the speed and efficiency of commissioning and testing the various schemes. The test procedures as well as test system to achieve a fully automatic test of the complete scheme will be presented.
Date of Conference: 17-20 March 2008