The Momentary Average Interruption Frequency Index (MAIFI) is a

reliability index Reliability index is an attempt to quantitatively assess the reliability of a system using a single numerical value. The set of reliability indices varies depending on the field of engineering, multiple different indices may be used to characterize ...

used by

electric power Electric power is the rate at which electrical energy is transferred by an electric circuit. The SI unit of power is the watt, one joule per second. Standard prefixes apply to watts as with other SI units: thousands, millions and billions ...

utilities A public utility company (usually just utility) is an organization that maintains the infrastructure for a public service (often also providing a service using that infrastructure). Public utilities are subject to forms of public control and ...

. MAIFI is the average number of momentary interruptions that a customer would experience during a given period (typically a year). Electric power utilities may define momentary interruptions differently, with some considering a momentary interruption to be an outage of less than 1 minute in duration while others may consider a momentary interruption to be an outage of less than 5 minutes in duration.

Calculation

MAIFI is calculated as

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Reporting

MAIFI has tended to be less reported than other reliability indicators, such as

SAIDI A Ṣa‘īdī (, Coptic: ⲣⲉⲙⲣⲏⲥ ''Remris'') is a person from Upper Egypt (, Coptic: ⲙⲁⲣⲏⲥ ''Maris''). Etymology The word literally means "from Ṣa‘īd" (i.e. Upper Egypt), and can also refer to a form of music or ...

SAIFI The Muslim Saifi, or sometimes pronounced Barhai are Muslim community, found in North India. They are also known as Saifi which denotes the Muslim sub-caste of blacksmiths and carpenters. A small number are also found in the Terai region of Nep ...

, and CAIDI. However, MAIFI is useful for tracking momentary power outages, or "blinks," that can be hidden or misrepresented by an overall outage duration index like SAIDI or SAIFI.

Causes

Momentary power outages are often caused by transient faults, such as lightning strikes or vegetation contacting a power line, and many utilities use reclosers to automatically restore power quickly after a transient fault has cleared.

Comparisons

MAIFI is specific to the area ( power utility, state, region, county, power line, etc. ) because of the many variables that affect the measure: high/low lightning, number & type of trees, high/low winds, etc. Therefore, comparing MAIFI of one power utility to another is not valid and should not be used in this type of benchmarking. It also is difficult to compare this measure of reliability within a single utility. One year may have had an unusually high number of thunderstorms and thus skew any comparison to another year's MAIFI.

References

{{Reliability indices Electric power Reliability indices