4.2. ERMUSR 02-15-2011i
Elk River
Municipal Utilities
] 3069 Orono Parkway • P.O. Box 430
Elk Raver, 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:
Febru 15, 2011 4.2
SUBJECT:
U dated 2010 Electric Reliabilit Re or[
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. This report was provided to the Utilities Commission in
January 2011.
DISCUSSION:
This report was a focus of discussion at the Staff update following the January Utilities Commission
meeting. Staff discussed the major outages of the year and the impact that the quick response has on
these reliability numbers. Also, the staff s sense of ownership in the system and high level of
workmanship contribute to the system reliability and customer service that are quantified through these
indexes.
During this discussion it was discovered that there was one outage that was inadvertently omitted. On the
fast Saturday of August in 2010 there was a storm that came through Elk River. During this storm, our
Substation 14 Bank 3 (located near the Great River Energy Energy Recovery Station) experienced a
substation transformer protection component failure due [o a lighting strike. This component failure
caused the protective breaker upstream of the substation transformer to open. Our crews responded
quickly to transfer the load to the adjacent Substation 14 Bank 4. Although this was a relatively short
outage late at night, it did affect a large number of people. Adding this outage doesn't significantly
change the overall reliability numbers. However to insure accurate reporting, below are the revised
system reliability numbers for 2010:
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 99.985% Availability. Last year was 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 [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 94 minutes. Last yeaz's CAIDI was 137 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 [he 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 80.0 minutes. Last year's SAIDI was 5.1 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. I[ 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 0.853. Last year's SAIFI was 0.037.
Another statistic staff gets concerned about is the average length of any outage. Elk River Municipal
Utilities' 2010 average length of outage is 108.11 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.
ACTION REQUESTED:
No action is required.