Mitigation of System Disturbances in an Interconnected Power Grid for the Southern African Power Pool

Lawrence Musaba, Sydney Zimba, and Andrew Obok Opok


system disturbance, damping, small signal stability, transfer capability, transient stability, interconnected power grid


The paper presents mitigation measures and recommendations to overcome major power system disturbances in SAPP system following system disturbances and outcome of investigations during 2008. Power system consultants and specialists from SAPP power utility members conducted steady state, dynamic and small signal power system studies to determine the root causes of the disturbances. The main causes of the disturbances were traced to poor damping of power system oscillations; risks and vulnerability of SAPP system to transient stability; and unsafe transfer limits through transmission corridors. Measures implemented to mitigate system disturbances were fitting or tuning PSS (Power Systems Stabilizers) and governors. For mitigating against future disturbances it was recommended that SVCs (Static Voltage Compensators) and FACTS (Flexible AC transmission Systems) devices and equipment should be installed in transmission locations identified from the investigation. The paper offers significant insights into the root causes of system disturbances in large power grids; how to improve operation of large scale power grids; improving system performance through redesign and placement of desirable plant such as FACTS or PSS to improve system damping or transfer capability.

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