Loading...
5.2. ERMUSR 02-14-2012Elk Rivers-= Municipal Utilities 13069 Orono Parkway • P.O. Box 430 Elk River, MN 55330-0430 UTILITIES COMMISSION MEETING Phone: 763.441.2020 Fax: 763.441.8099 TO: FROM: Elk River Municipal Utilities Commission Troy Adams, P.E. -Director of Operations John Dietz, Chair Daryl Thompson, Trustee Al Nadeau MEETING DATE: AGENDA ITEM NUMBER: Feb 15, 2011 5.2 SUBJECT: U dated 2011 Electric Reliability Re ort BACKGROUND: Minnesota Rules Chapter 7826 Public Utilities Commission Electric Utility Standards cover safety, reliability, service, and reporting requirements. Per 7826.0100(A), municipal utilities aze exempt from these requirements. However, the Elk River Municipal Utilities Commission adopted a number of parts of this chapter as a Distribution Reliability Standard policy requiring annual reporting on system reliability. DISCUSSION: Even with the weather issues during 2011, our reliability index numbers aze excellent. These reliability index numbers reflect the condition of our robust electrical system as well as the superb response time from our local line crews. This also reflects the local accountability, long term visioning on system design, and ongoing system maintenance. The table below reflects the number of customer outage minutes from 2002 through 2011. Year # of Customers # of Outa a Minutes # of Outa es 2002 6669 356,340 50 2003 7193 39,285 54 2004 7773 393,926 84 2005 8398 558,140 59 2006 8804 314,510 73 2007 9163 67,845 47 2008 9067 155,768 57 2009 9170 46,706 49 2010 9207 526,144 77 2011 9576 297,359 51 A number of reliability indexes aze used in the electric industry to make it easier to compaze performance of electric utilities. These reliability indexes are: 1. ASAI (average service availability index) ASAI is a measure of the average availability of the sub-transmission and distribution systems to serve customers. It is the ratio of the total customer minutes that service was available to the total customer minutes available in a time period. This is normally expressed as a percentage. ERMU's 2011 ASAI is 99.994% Availability. Last yeaz was 99.985% Availability. 2. CAIDI (customer average interruption duration index) This is defined as the average length of an intemxption weighted by the number of customers affected. It is calculated by summing the customer minutes off during each interruption in the time period and dividing this by the number of customers experiencing one or more sustained interruptions during the time period. The resulting unit is minutes. The index enables utilities to report the average duration of a customer outage for those customers affected. ERMU's 2011 CAIDI is 105 minutes. Last yeaz's CAIDI was 94 minutes. 3. SAIDI (system average interruption duration index) This is defined as the average interruption duration for customers served during a specified time period. It is determined by summing the customer minutes off for each interruption during a specified time period and dividing that sum by the average number of customers served during that period. The unit is minutes. This index enables the utility to report how many minutes customers would have been out of service if all customers were out at one time. ERMU's 2011 SAIDI is 31.1 minutes. Last yeaz's SAIDI was 80.0 minutes. 4. SAIFI (system average interruption frequency index) This is defined as the average number of timers that a customer is interrupted during a specified time period. It is determined by dividing the total number of customers interrupted in a time period by the average number of customers served. The resulting unit is "interruptions per customer." ERMU's 2011 SAIFI is 0.296. Last yeaz's SAIFI was 0.853. Another statistic staff gets concerned about is the average length of any outage. Elk River Municipal Utilities' 2011 average length of outage is 126.00 minutes. Last year the average length of outage was 108.11 minutes. Electric utilities with a high percentage of underground facilities will exhibit higher length of outage time than electric utilities with more overhead facilities. Staff reviews these statistics in detail to find ways to continually improve our system. These statistics are very good compared to other utilities. Underground faults and branches caused the greatest number of outages. Underground faults resulted in 17.65% of our outage incidents, but only contributed to 0.99% of total outage time. Outages resulting from branches and/or trees make up 25.49% of our outage incidents and contribute to 33.46% of our outage time. This is partially due to the unusually wet spring which resulted in trees being susceptible to blowing down during storms. Ongoing and increased efforts should be taking for tree trimming to improve this outage category. Overall, weather related outages account for 13.73% of the incidents and 46.86% of our outage time. There were a few significant storm events in combination with the branches/tree incidents that affected our reliability. One of these events occurred when lightning struck our West 1 Substation located adjacent to the City's Public Works building. Another occurred when a strong wind storm took out the overhead feeder that runs along US HWY 169 to the Landfill Gas-to-Electric Generation Plant. Many investor owned and cooperative run utilities "storm normalize "their reliability numbers by removing "major outages" due to storms from their reliability index number calculations. Our reliability numbers have not been storm normalized. Our numbers reflect these major outages and represent what our customer actually experienced in 2011. Overall, our electric distribution system is robust and our reliability is very high. ACTION REQUESTED: No action is required.