5.1. ERMUSR 01-12-2010Elk River
Municipal Utilities
13069 Orono Parkway • P.O. Box 430
Elk River, MN 55330-0430
January 6, 2010
To: Elk River Municipal Utilities Commission
John Dietz
Jerry Gumphrey
Daryl Thompson
From: Troy Adams
Subject: Review 2009 Electric Reliability Report
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Phone: 763.441.2020
Fax: 763.441.8099
The Minnesota Energy, Security and Reliability Act requires electric distribution utilities to file an annual
outage report to their governing bodies, which in our case, to the Elk River Municipal Utilities
commission.
The attached spread sheet reflects the outage history for 2009. Animals and branches continue to cause
the greatest number of outages. Underground faults were also a contributing factor. The single greatest
incident impacting the report is a car accident where the vehicle hit a pole.
The table below reflects the number of customer outage minutes from 2002 through 2009.
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
A number. of reliability indexes are used in the electric industry to make it easier to compare 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 2009 ASAI is 99.999%. Availability
2. CAIDI (customer average interruption duration index)
This is defined as the average length of an interruption 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 2009 CAIDI is 137 minutes. Last year's CAIDI was 28 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 2009 SAIDI is 5.1 minutes. Last year's SAIDI was 17.3 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 2009 SAIFI is 0.037. Last year's SAIFI was 0.618.
Another statistic staff gets concerned about is the average length of any outage. Elk River Municipal
Utilities' 2009 average length of outage is 109.3 minutes. Last year the average length of outage was
99.3 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 has reviewed these statistics in detail to find ways to improve. These statistics are very good
compared to other utilities. While other utility stats are difficult to obtain, these are some typical numbers
we have found:
ERMU
2009 Connexus
2008 MN Power
2008
CAIDI 137 min 78 min 100 min
SAIDI 5.1 min 29 min 114 min
SAIFI 0.037 0.372 1.140
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