Availability of Power Stations and Their Equipment
Comprehensive and self-consistent data relating to plant availability and outage rates are essential for the assessment of plant performance, thereby enabling standby requirements to be estimated, plant extensions planned and the performance of different types of plant compared. The present paper deals with the essential requirements that must be met to ensure the comparability and adequacy of the statistical data. Five main points are emphasized in the paper: the assessment of plant performance is best given by outage rates, stated in terms of time; three classes of outage are described; namely forced, deferable and planned. Shortfall is considered separately; since the practical consequences of the three kinds of outage will in general be very different, and since one may affect another the record must always include the three outage rates shown as separate items; to permit the assessment and comparison of statistics from different sources the record should also include an output factor—(total output of item during period/rated capacity x total hours in period), a service factor—(total hours of item in service during period/total hours in period) and the number of starts during the period under review; statistics from plants of very dissimilar properties and design and with widely different operating regimes should be compared cautiously.