What does SAIFI stand for? 

SAIFI

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 = ∑ λ i N i ∑ N i {\displaystyle {\mbox{SAIFI}}={\frac {\sum {\lambda _{i}N_{i}}}{\sum {N_{i}}}}} where λ i {\displaystyle \lambda _{i}} is the failure rate and N i {\displaystyle N_{i}} is the number of customers for location i {\displaystyle i} . In other words, SAIFI = total number of customer interruptions total number of customers served {\displaystyle {\mbox{SAIFI}}={\frac {\mbox{total number of customer interruptions}}{\mbox{total number of customers served}}}} 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.

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