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sustained interruptions during the time period. The resulting unit is minutes. The index <br />enables utilities to report the average duration of a customer outage for those customers <br />affected. <br />ERMU's 2005 CAIDI is 111.43. <br />3. SAIDI (system average interruption duration index) <br />This is defined as the average interruption duration for customers served during a <br />specified time period. It is determined by summing the customer-minutes off for each <br />interruption during a specified time period and dividing the sum by the average number <br />of customers served during that period. The unit is minutes. This index enables the <br />utility to report how many minutes customers would have been out of service if all <br />customers were out at one time. <br />ERMU's 2005 SAIDI is 66.46. We do not as yet have a feel for this number if it is good, <br />average, or bad. <br />4. SAIFI (system average interruption frequency index) <br />This 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 customers <br />interrupted in a time period by the average number of customers served. The resulting <br />unit is "interruptions per customer". Separate SAIFI indexes are sometimes calculated <br />for long and for short interruptions. <br />ERMU's 2005 SAIFI is .596. <br />Another statistic staff gets concerned about is the overage length of any outage. ERMU's <br />2005 average length of outage is 83.56 minutes. Electric utilities with a high percent of <br />underground facilities will exhibit higher length of outage times than electric utilities <br />with high percent of overhead facilities. We are currently trying to find these statistics <br />from other electric utilities. <br />Staff has reviewed these statistics in detail to find ways to improve. These statistics are <br />in general very complementary to ERMU. Glenn Sundeen and his department continue <br />to do an outstanding job in constructing, operating and maintaining an electrical system <br />particularly in a fast growing area. <br />Other utilities statistics on CAIDI, SAIDI, and SAIFI are still difficult to obtain and <br />entities play some games with these numbers. Below is a table reflecting proposed 2004 <br />numbers by Minnesota Public Utilities Commission (MPUC), for State IOU. <br /> SAIDI SAIFI CAIDI <br />Minnesota Power 137.5 1.09 125.7 <br />Otter Tail Power 69 to 42 23 to 11.8 4.44 to 1.8 ? <br />Xcel 172 to 98 9.4 to 1.44 119 to 94 <br />Elk River Municipal Utilities 66 .596 11 1 <br />