20 CSR 4240-23.010
Electric Utility System Reliability Moni
toring and Reporting Submission Requirements
PURPOSE: This rule establishes reliability monitoring and report
ing requirements for electrical corporations.
(1) Information Reported. Commencing with the month follow
ing the month in which this rule becomes effective, each elec
trical corporation (as defined in section 386.020, RSMo) shall
accumulate the following information (on a monthly basis):
(A) System Average Interruption Frequency Index (SAIFI),
which reflects the average frequency of service interruptions
in number of occurrences per customer and is defined as the
total number of customer interruptions for the period covered
divided by the total number of customers served;
(B) Customer Average Interruption Frequency Index (CAIFI),
which reflects the average number of interruptions per cus
tomer interrupted and is defined as the total number of cus
tomer interruptions for the period covered divided by the total
number of customers affected;
(C) System Average Interruption Duration Index (SAIDI),
which reflects the average interruption in hours or minutes
per customer served for the period covered and is defined as
the sum of all customer interruption durations divided by the
total number of customers served; and
(D) Customer Average Interruption Duration Index (CAIDI),
which reflects the average interruption duration and is defined
as the sum of all customer interruption durations divided by
the total number of customers interrupted.
(2) Filing of Report. The information required by section (1)
shall be filed annually by the last business day of April of the
calendar year following the calendar year for which the infor
mation was accumulated to the manager of the commission’s
energy department, or the manager’s designee, electronically
in tabular and graphical formats.
(3) Adjustment of Data. The information required by section (1)
shall be filed both unadjusted and adjusted to exclude major
storm events per IEEE Standard 1366-2003, Guide for Electric
Power Distribution Reliability Indices.
(4) Scope of Information. The information required by section
(1) shall be reported for all Missouri retail electric customers of
the electrical corporation.
(5) Interruptions Not to Be Reported. The following interrup
tion causes shall not be included in the calculation of the reli
ability indices required by section (1):
(A) Interruptions initiated pursuant to the provisions of an
interruptible service tariff or contract and affecting only those
customers taking electric service under such tariff or contract;
(B) Interruptions due to nonpayment of a bill;
(C) Interruptions due to tampering with service equipment;
(D) Interruptions due to denied access to service equipment
located on the affected customer’s private property;
(E) Interruptions due to hazardous conditions located on the
affected customer’s private property;
(F) Interruptions due to a request by the affected customer;
(G) Interruptions due to a request by a law enforcement
agency, fire department, other governmental agency responsi
ble for public welfare, or any agency or authority responsible
for bulk power system security or reliability; or
(H) Interruptions caused by the failure of a customer’s equip
ment; the operation of a customer’s equipment in a manner
inconsistent with law, an approved tariff, rule, regulation, or an
agreement between the customer and the electrical corpora
tion; or the failure of a customer to take a required action that
would have avoided the interruption, such as failing to notify
the electrical corporation of an increase in load when required
to do so by a tariff or contract.
(6) Worst Performing Circuits. Each electrical corporation shall
establish and maintain a program for identifying and analyzing
its worst performing circuits during the course of each calen
dar year. The program shall include, but should not be limited
to, an analysis of the top five percent (5%) worst performing
circuits used to serve the electrical corporation’s Missouri retail
electric customers. The worst performing circuits shall be iden
tified and ranked using SAIFI values computed for each circuit,
adjusted to exclude major storm events per IEEE Standard 13662003, Guide for Electric Power Distribution Reliability Indices
and in any other manner chosen by the electrical corporation.
The SAIDI value for each circuit shall also be listed.
(7) The information developed in accordance with section (6)
shall be reported as part of the annual report required by sec
tion (2) and shall also include actions taken (or planned) to im
prove the performance of the circuits identified in section (6).
(8) Multi-Year Worst Performing Circuit Reporting. If, on or after
the time the annual report required by section (7) for calendar
year 2011 is filed, a circuit has been on the worst performing
circuit list for any two (2) of the three (3) most recent consec
utive calendar years, the electrical corporation shall include
detailed plans and schedules for improving the performance
of that circuit in addition to the other information required by
section (7). Such plans and schedules may vary from circuit to
circuit based on differences in geography or other local condi
tions, customer density, and cost considerations.
(9) Reliability Improvement Programs. Each electrical corpora
tion shall transmit to the manager of the energy department of
the commission, or the manager’s designee, no later than the
last business day of December each year: A summary report de
tailing all programs scheduled for the upcoming calendar year
designed to maintain or improve service reliability. The infor
mation shall be reported by regional/district/division operating
areas, if the electrical corporation’s operations are divided into
regions/districts/divisions. This report shall include funding
levels and the status of each of these programs. The first such
report shall be transmitted no later than December 31, 2008.
(10) Residential Subdivision Undergrounding. Where reason
able and consistent with utility easements and applicable law,
electrical corporations are to locate all newly installed elec
trical corporation-owned residential subdivision distribution
facilities underground. This provision applies to residential
subdivisions with average lots no larger than 0.5 acres. As used
in this provision, subdivision distribution facilities refer to ter
minal poles, manholes, feeder lines, service lines, switchgear,
pad-mounted, pole-mounted, or submersible transformers,
and pedestals utilized to provide electric service to subdivi
sions but does not include subtransmission lines and three
(3)-phase distribution feeders/backbone circuits (portion of
AND INSURANCE
distribution system directly interconnected with distribution
substation and prior to the first protective device). If an elec
tric corporation determines that it is not reasonable to place
a residential subdivision’s distribution facilities underground
and the subdivision has average lots no larger than 0.5 acres,
the electrical corporation shall maintain records available for
Public Service Commission (PSC) inspection to demonstrate
why undergrounding was unreasonable.
(11) Comparison of Reliability Metrics. The commission may
accumulate the information required by section (1) from the
electrical corporations and provide this information to the pub
lic. Such disclosure shall include a statement that such indices
are affected by customer density, tree density, geography, ob
served weather, and other factors that may be beyond the con
trol of the electrical corporation. Further, the commission may
release comparisons of this data with similar data from other
states but in doing so shall include in the release any caveats
that would explain differences in the indices. These caveats
shall include, but are not limited to, differences in calculation
methodologies.
(12) Variances. A variance from a provision of this rule may be
granted for good cause shown.
AUTHORITY: sections 386.040, 386.250, 386.310, and 393.140,
RSMo 2000 and section 393.130, RSMo Supp. 2007.* This rule orig
inally filed as 4 CSR 240-23.010. Original rule filed Jan. 15, 2008,
effective July 30, 2008. Moved to 20 CSR 4240-23.010, effective Aug.
28, 2019.
*Original authority: 386.040, RSMo 1939; 386.250, RSMo 1939, amended 1963, 1967,
1977, 1980, 1987, 1988, 1991, 1993, 1995, 1996; 386.310, RSMo 1939, amended 1979,
1989, 1996; 393.130, RSMo 1939, amended 1949, 1967, 2002; and 393.140, RSMo 1939,
amended 1949, 1967.