Short-term generating unit maintenance scheduling in a deregulated power system using a probabilistic approach

Overall evaluation of generating system adequacy appears to be declining in the new utility environment despite the fact that severe power shortages have occurred in jurisdictions such as California and Alberta due to inadequate generating facilities. The installed generating capacity should be capable of meeting the system load in the face of capacity outages and the removal of selected generating units for scheduled maintenance. In a deregulated utility environment, capacity shortages can be created by a lack of coordination in scheduling generating unit maintenance. This can be avoided by having impending maintenance requirements scheduled by the independent system operator. The objective in scheduling preventive maintenance should be to ensure that the resulting risk does not exceed a predetermined acceptable level. In a deterministic approach, the acceptable margin is either, a percentage of the available capacity or load, or a value equal to the largest loaded unit. A methodology for maintenance scheduling is presented that combines a probabilistic approach and an acceptable deterministic criterion into a single framework. This methodology is designated as the health levelisation technique. The effect of conducting preventive maintenance with different load profiles is illustrated. The concepts presented are illustrated by application to the RBTS.