SAIFI

The System Average Interruption Frequency Index (SAIFI)^[1] is commonly used as a reliability indicator by electric power utilities. SAIFI is the average number of interruptions that a customer would experience, and is calculated as

${\displaystyle {\mbox{SAIFI}}={\frac {\sum {\lambda _{i}N_{i}}}{N_{T}}}}$

where $\lambda _{i}$ is the failure rate, $N_{i}$ is the number of customers for location $i$ and ${\displaystyle N_{T}}$ is the total number of customers served. In other words,

${\displaystyle {\mbox{SAIFI}}={\frac {\mbox{total number of customer interruptions}}{\mbox{total number of customers served}}}}$

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.

References

1. Yeddanapudi, Sree. "Distribution System Reliability Evaluation". Iowa State University. Retrieved 18 June 2011.

See also

• Average Service Availability Index (ASAI)
• ASIDI
• ASIFI
• ASUI
• CAIDI
• CAIFI
• CTAIDI
• MAIFI
• SAIDI
• SAIFI