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Listed below are a number of reliability indices that are used bythe electric industry to make it <br />easier to compare performance among utilities, along withERMU’s 2018 and 2019 statistics. <br />Average Service Availability Index (ASAI) <br />ASAI is a measure of the average availability of the sub-transmission and distributionsystems <br />to serve customers.It is the ratio of the total customer minutes that service was available to <br />the total customer minutes available in a time period. This is normally expressed as a <br />percentage. <br /> <br />ERMU’s 2019 ASAI is 99.9951% Availability ERMU’s 2018 ASAI is 99.9980% Availability <br /> <br />Customer Average Interruption Duration Index (CAIDI) <br />CAIDI is defined as the average duration (in minutes) of an interruption experienced by <br />customers during a specific time frame.It is calculated by summing the customer minutes off <br />during each sustained¹ interruption in the time period and dividing this by the number of <br />customers experiencing one or more sustained¹ interruptions during the time period. The <br />resulting unit is minutes. The index enables utilities to report the average duration of a <br />customer outage for those customers affected. <br /> <br />ERMU’s 2019 CAIDI is 60.111 minutes ERMU’s 2018 CAIDI is 58.147 minutes <br /> <br />System Average Interruption Duration Index (SAIDI) <br />SAIDI is defined as the average interruption duration (in minutes) for customers served <br />during a specified time period.It is determined by summing the customer minutes off for each <br />sustained¹ interruption during a specified time period and dividing that sum by the average <br />number of customers served during that period. The resulting unit is minutes. This index <br />enables the utility to report how many minutescustomers would have been out of service if all <br />customers were out at one time. <br />ERMU’s 2019 SAIDI is 25.412 minutes ERMU’s 2018 SAIDI was 10.009 minutes <br />System Average Interruption Frequency Index (SAIFI) <br />SAIFI is defined as the average number of times that a customer is interrupted during a <br />specified time period.It is determined by dividing the total number of sustained¹ interrupted <br />customers in a time period by the average number of customers served. The resulting unit is <br />“interruptions per customer.” <br /> <br />ERMU’s 2019 SAIFI is 0.423 ERMU’s 2018 SAIFI was 0.172 <br /> <br /> <br />¹ Only outages lasting longer than five minutes are included in the calculations, as defined by IEEE 1366. <br />______________________________________________________________________________ <br />Page 2 of 3 <br />53 <br />