SAIFI explained

The System Average Interruption Frequency Index (SAIFI) is commonly used as a reliability index by electric power utilities. SAIFI is the average number of interruptions that a customer would experience, and is calculated as

SAIFI = (\sum{ λ _{i} N _{i})/() }

where

λ _{i} is the failure rate and N _{i} is the number of customers for location i . In other words,SAIFI = (totalnumberofcustomerinterruptions)/(totalnumberofcustomersserved)

SAIFI is measured in units of interruptions per customer. It is usually measured over the course of a year, and according to IEEE Standard 1366-1998 the median value for North American utilities is approximately 1.10 interruptions per customer.

Sources

• Web site: Layton . Lee . Electric System Reliability Indices . www.egr.unlv.edu . 2004.