Empirical Study of Power System Stability Following Generator Tripping Events at Egbin Thermal Power Station

This study empirically analyses power system stability responses following generator tripping events at Egbin Thermal Power Station in Lagos State, South West Nigeria, using historical disturbance data and validated dynamic system simulations. Egbin, as Nigeria's largest thermal power station with an installed capacity of 1,320MW, contributes a disproportionately large fraction of the national grid's synchronous generation, making its unit trips among the most destabilising events for Nigeria's interconnected power system. Historical system event data for 38 generator trip events at Egbin over a two-year period were obtained from the Transmission Company of Nigeria's SCADA system records, capturing pre-disturbance generation level, post-trip frequency nadir, rate of change of frequency, and system restoration time for each event. A dynamic simulation model of the Nigerian grid was developed in PSSE using validated generator parameters and governor characteristics. Transient stability and frequency stability simulations were run for the identified trip events, and simulation results were compared against actual recorded system responses to validate the model. Validated model runs were then used to analyse the critical clearing time for Egbin unit trips and to evaluate the effectiveness of existing under-frequency load shedding scheme settings in arresting frequency decline. Results confirm that trips of Egbin units above 150MW without adequate frequency response from remaining generators breach the ENTSO-E frequency quality standard minimum frequency criteria in 71 percent of simulated cases. Recommendations include increasing fast-response frequency containment reserve allocation during periods of high Egbin contribution. Keywords: power system stability, frequency response, generator tripping, Egbin, transient stability.