5.2. ERMUSR 01-11-2011Elk River
Municipal Utilities
L3069 Oroou Parkway • PO. Box +30
ftlk River, MN 553311-0430
UTILITIES COMMISSION MEETING
Phone: 763.441.2020
Fax: ?fi3 d11B099
TO: FROM:
Elk River Municipal Utilities Commission Troy Adams, P.E. -Director of Operations
John Dietz, Chair
Daryl Thompson, 'T'rustee
--- -- --
MEETING DATE: -
AGENDA ITEM NUMBER:
January 11, 2011 5.2
- -- --
SUBJECT: -
Review 2010 Electric Reliability Report
BACKGROUND:
Minnesota Rules Chapter 7826 Public Utilities Commission Electric Utility Standards cover
safety, reliability, service, and reporting requirements. Per 7826.0100(A), municipal utilities are
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.
As the Commission is aware, Elk River Municipal Utilities won the 2010 System Innovation Award from
Minnesota Municipal Utilities Association. The award was presented [o ERMU "in recognition for its
leadership and innovation in customer service, energy efficiency, renewable energy or technology use,
which has improved service to its community and enhanced public power's prestige." One of the reasons
ERMU received this awards is our excellenC electrical system reliability. This trend continues. Even with
the weather issues during 20i0, our reiiabiiity index numbers are excellent. 'Chew reiiabiiity 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.
DISCUSSION:
The table below reflects the number of customer outage minutes from 2002 through 2010.
Year # of Customers # of Outage Minutes # of Outages
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
2008
2009 _
2010 9163
9067
9170 _
9207 67,845
155,768
___ 46,706 _
526,144 47
57
49
77
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 2010 ASAI is 99.989%. Availability
2. CALDI (customer average interruptiou duration index)
This is defined as the average length of an interruption weighted by the number of customers affected.
[t is calculated by summing the customer minutes off during each interruption in the time period and
dividing [his 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 2010 CAIDI is 108 minutes. Last year's CAIDI was 137 minutes.
3. 5AIDI (system average interruptiou duratiou iudex)
This is defined as the average interruption duration for customers served during a specified time
period. [t is determined by summing the customer minutes off for each intemrption 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 2010 SAIDI is 57.2 minutes. Last year's SAIDI was 5.1 minutes.
4. SAIFI (system average iuterrupHon frequency index)
This is defined as the average number of timers that a customer is interrupted during a specified time
period. [t 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 2010 SAIFI is 0.527. Last year's SAIFI was 0.037.
Another statistic staff gets concerned about is the average length of any outage. Elk lover lvlunicipai
Utilities' 2010 average length of outage is 105.8 minutes. Last year the average length of outage was
109.3 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 reviews these statistics in detail to find ways to continually improve our system. 'these statistics are
very good compared to other utilities. Attached for you reverence are graphs depicting our ASAI, CA[Dl,
SAIDI, and SA1FI numbers. Animals and branches continue to cause the greatest number of outages.
Animals contributed to 21 outages in 2010 and branches contributed to 14 outages. Underground faults
were also a contributing factor. The single greatest incident impacting the report was the squirrel that
caused the Substation 14-3 transformer to go off line one Sunday morning in August. This outage
affected 3,000 customers for 75 minutes resulting in a 225,000 minute component, or 42.8%, of the total
526,144 minutes of outage. The specific area where this squirrel caused the flashover between feeders
has been on our capital projects 2012 forecast for modifications that help to prevent this type of outage.
hi the short term until this system improvement is made, there have been some system protective relays
setting improvements made. To proactively reduce the number of outages directly related [o branches,
and sometimes indirectly related to animals, staff continues to do tree trimming. Overall, our electric
distribution system is robust and our reliability is very high.
ACTION REQUESTED:
No action is required.
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