Reliability indices

predicted elapsed time between inherent failures of a system during operation

The system average interruption duration index (SAIDI) is commonly used as a reliability index by electric power utilities. SAIDI is the average cumulative outage duration for each customer served, and is calculated as:

measure of the maintainability of repairable items; average time required to repair a failed component or device

The System Average Interruption Frequency Index (SAIFI) is commonly used as a reliability index by electric power utilities. This index measures the average number of times that a system customer experiences an outage during the year or during a given time period.

The Customer Average Interruption Duration Index (CAIDI) is a reliability index commonly used by electric power utilities. It is related to SAIDI and SAIFI, and is calculated as