The problem addressed is the Power Plant Preventive Maintenance Scheduling. The problem is taken from the power industry and it requires determining the perioThis paper addresses the Power Plant Preventive Maintenance Scheduling Problem. The problem is taken from the power industry, where providing electric energy to the consumers without interruption is of high importance. This problem is usually treated in the long-term exploitation of electric production systems. It requires determining the period for which generating units of an electric power utility should be taken offline for planned preventive maintenance over a time horizon, usually on a yearly basis. The objective is to minimize the total operating cost while a set of constraints is satisfied, with emphasis on realiability.