There are various parameters for the supply reliability of the power supply system, from which the interruption frequency, the interruption duration or the unavailability of the power supply system can be derived.
The System Average Interruption Frequency Index (SAIFI) is the average frequency of interruptions. The SAIFI index shows how often a consumer is affected by a power interruption on average per year. The SAIFI index is calculated as the ratio of the total number of interruptions to the total number of consumers. The measurements are taken over a certain period of time, usually one year. The SAIFI value is given in the quotient of one year. (1/a).