Development of Excitation System Modelling Approaches for the Nigerian Grid

The structure of the Nigerian interconnected system, which includes long power lines and a small number of generators, leads to technical challenges to stability of the interconnection. The static models of the Nigerian high voltage system indicate certain system deficiencies and weak points, but records and observations of system collapses suggest that swing instabilities are sometimes part of rapid frequency decline. A dynamic model of system behavior can help determine whether system stability is major limiting factor for system operation, enable better forensic analysis of blackout events, lead to proposals for mitigating measures within the reach of operators. Accurate modelling of generator excitation systems represents a critical first step in the development of robust dynamic models-but validated excitation system parameters are not necessarily available for all generators, for when not all parameters are available, this paper establishes and tests a procedure that is used to select credible parameters. The paper demonstrates how one can build acceptable power system model that supports preliminary benchmarking and validation.