Optimal maintenance scheduling of thermal power unıts in a restructured nigerian power system

The optimal preventive maintenance schedules of generating units for the purpose of maximizing economic benefits and improving reliable operation of 44 functional thermal generating units of Nigerian power system, subject to satisfying system load demand, allowable maintenance window and crew constraints over 52 weeks maintenance and operational period is presented. It uses HPSO algorithm to find the optimum schedule. The purpose of the algorithm is to orderly encourage moving maintenance outages from periods of low reliability to periods of high reliability, so that a reasonable reliability level is attained throughout the the year. The maintenance outages for the generating units were scheduled to minimize the sum of the squares of reserves and satisfy 2,943.8 MW system peak load with 6.5% spinning reserve of 2,403.8 MW, available manpower for maintenance per week of 22 and maximum generation of 3,028.8 MW. The reliability criterion of the power system was achieved by maximizing the minimum net reserves along with satisfaction of maintenance window, crew and load constraints. The population size of 30 particles and 2500 iterations were chosen. These were chosen as a trade-off between computational time and complexity. It was shown that the HPSO algorithm is not as time efficient as the standard PSO but it provides more consistent and reliable results. In the periods of low maintenance activities, with the PSO algorithm, the maximum generation is 2,753.8 MW while the HPSO produce 2,943.8 MW. It is glaring from the comparison that the HPSO algorithm shows better performance and produce optimal maintenance scheduling framework for the Nigerian power system that will achieve better utilization of available energy with improved reliability and reduction in energy cost.   Key words: Generator maintenance, deregulated market, optimization.