Saifi

The System Average Interruption Frequency Index (SAIFI) 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 ${\displaystyle \lambda _{i}}$ is the failure rate, ${\displaystyle N_{i}}$ is the number of customers for location ${\displaystyle i}$ and ${\displaystyle N_{T}}$ is the total number of customers served. In other words,

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