The Application of Planning Criteria to the Determination of Generator Service Dates by Operational Gaming

One of the important considerations in determining criteria for system planning is the attitude of the customers toward the quality of service. This attitude is affected by at least six factors related to interruptions: the frequency, magnitude, duration, time of day, season of year, and apparent reason for the interruption. Estimates of the effects of varying these factors have been obtained by collecting opinions of a group of supervisors and management personnel who are directly concerned with quality of electric service. Among other results, this study produced a quantitative estimate of how rapidly dissatisfaction increases with increases in frequency, magnitude, and duration of outage. Apparently duration is particularly important. The study also developed factors for taking into account the effect of outages occurring at different seasons of the year. This data has been incorporated in a mathematical model which determines, by simulation, dates when generator capacity and interconnection additions are required. The model determines the dates on the basis of a relatively constant risk of shortage of capacity, modified by customer reaction to recent results of earlier applications of this policy. The level of risk is based on a ratio of load to capacity. The threshold level for installing additional capacity is affected by the accumulated dissatisfaction resulting from previous load-reduction measures. Recent events are given greater weight in this decision. A series of misfortunes is followed by a period of greater conservatism, expressed by lower threshold levels of the availability index.