12. Generating Capacity Methods

Several methods, measures or indicators have been developed for assessment of reliability of power systems. A single formula or technique, which would give all the answers, does not exist, because the power systems are far too complex for this to be possible. Selected methods, measures and indicators are summarized from the point of view of generating power and energy which is produced in power plants. Generation reserve margin is a measure, which shows how the capacity of power system exceeds the peak consumption. Percent reserve evaluation is calculated by comparing the total installed generating capacity at peak with the peak load. The loss of load probability is defined as the probability of the system load exceeding available generating capacity under the assumption that the peak load is considered as constant through the day. The loss of load probability does not really stand for a probability. It expresses statistically calculated value representing the percentage of hours or days in a certain time frame, when energy consumption cannot be covered considering the probability of losses of generating units. The frequency and duration method utilizes the transition rate parameters ? and ? in addition to availability and unavailability. Parameter ? represents failure rate. Parameter ? represents the repair rate.