Adjusting Maintenance Schedules to Levelize Risk

When scheduling generating units for maintenance one of the goals is to level the risks of capacity shortages throughout the year. Level reserves have been used as an indication of level risk. This paper illustrates that better schedules can be found by a method that uses effective capability in place of reserve. The five step method of incorporating risk considerations into existing maintenance scheduling procedures is described and illustrated. The same capacity outage probability table as used in the loss-of-load probability method is used to determine the effective load-carrying capability of each unit to be scheduled. These effective capabilities take the place of the unit ratings in the reserve leveling portion of existing procedures. The loads forecast for each maintenance period are also converted into an equivalent load which reflects the variability of peak loads during the period.