An Interactive Package for Risk Evaluation and Maintenance Scheduling

The calculation of the Loss of Load Probability (LOLP) is an important element in generation planning studies. LOLP is calculated either independently to evaluate the risk of a certain generation system or in conjunction with several planning application programs such as, generator maintenance scheduling, probabilistic production costing, hydrothermal scheduling, generation expansion, etc. Exact calculation of the LOLP requires the calculation of the Capacity Outage Probability Table (COPT). This table takes into consideration the capacity rating the the forced outage rates of the generating units of the system and it provides the probability values associated with various amounts of system capacity on outage. The capacity outage table is calculated by utilizing the well known recursive convolution formula. Usually the table is simplified by rounding the capacity outage table to selected discrete capacity levels. The size of the round off increment depends on the desired accuracy. The classic approach is time consuming and requires a considerable amount of computer memory. In order to reduce the computational time and computer storage several methods have been proposed, in which the capacity outage probabilities are approximated with analytic continuous probability distributions. Most of these methods utilize the Central Limit Theorem, Fourier techniques and the Gram Charlier´s expansion. Closely related to the LOLP is the maintenance scheduling problem. Preventive maintenance is required for all generating units in order to reduce the probability of capacity shortage and improve the overall reliability of the power system.