reliability 101 appa 2005 e&o technical conference memphis, tn april 19, 2005 gregg turbeville,...

Reliability 101

APPA 2005 E&O Technical ConferenceMemphis, TN April 19, 2005

Gregg Turbeville, PESupv, Distribution PlanningSantee CooperMyrtle Beach, SC

4/19/2005 APPA 2005 E&O Technical Conference

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Reliability

General term that means different things to different

utilities.


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What is Reliability? Definition

1. the trait of being dependable or reliable (trustworthy, stable, unfailing) WordNet ® 2.0, © 2003 Princeton University


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What is Reliability? A subset of Power Quality Power Quality (sags, swells, transients, flicker,

harmonic distortion) Reliability: subset of power quality that

deals with customer interruptions. Availability - duration of interruptions Frequency of both sustained and

momentary Reliability Indices: calculated values based on

observed outage data for a set of loads, customers, feeders, territories, etc.


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IEEE 1366-2003

IEEE 1366 is the IEEE Guide for Electric Power Distribution Reliability Indices. present terms and definitions foster uniformity in development of indices identify factors which affect the indices aid in consistent reporting practices provide tools for internal and external

comparisons.


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IEEE 1366-2003

Started in 1992 as the IEEE Working Group on Distribution Reliability

IEEE 1366 issued in April 1999 as “Trial Use Guide for Electric Power Distribution Reliability Indices” [IEEE 1366-1998]

Updated in 2001 as “Full Use Guide” Major revision issued in April 2004


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Reliability Indices

What indices are you using to track and benchmark?


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Which indices are used?

SAIDI > 80% SAIFI 80% CAIDI 70% ASAI 60% MAIFI 20% Others 20%

(CAIFI, CTAIDI, CEMI, CEMSMI)


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SAIDI

System Average Interruption Duration Index

Total duration of interruption for the average customer

= Customer Interruption Durations Total number of customers served


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SAIDI example

100 customers on the system 14 customers experienced a 3-hour outage 14 x 3 = 42 hours or 2520 minutes

SAIDI = 2520 = 25.2 100

Average of 25.2 minutes per customer


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SAIFI

System Average Interruption Frequency Index

How often the average customer experiences a sustained interruption

= Total Number of Customers Interrupted Total number of customers served


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SAIFI example

100 customers on the system

60 customers had a sustained interruption(or 30 customers had two interruptions: 30 x 2 = 60)

SAIFI = 60 = 0.6 100


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CAIDI

Customer Average Interruption Duration Index

The average duration of interruptions per customer that had an interruption

The average time to restore service.

= Customer Interruption Durations

Total number of customers interrupted


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CAIDI example

100 customers on the system 10 customers experienced a 40-minute outage Cust. Int. Duration = 400 minutes Total number of customers interrupted = 10 CAIDI = 400 = 40

10 Average of 40 minutes per interrupted

customer.


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ASAI

Average Service Availability Index

The fraction of time (percentage) that a customer has received power during the reporting period.

= Customer Hours Service Availability Customer Hours Service Demands


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ASAI example

365 days x 24 hours/day = 8760 hours per year 100 customers 876,000 customer-hours 44 customers experience a 60-minute outage (2640

customer-minutes, or 44 customer-hours)

ASAI =876,000 – 44 = 875,956 = 876,000 876,000

= .99995 or 99.995%


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MAIFI

Momentary Average Interruption Frequency Index

The average frequency of momentary interruptions.

MAIFI = Total No. of cust. momentary interruptions Total number of customers served


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MAIFI example

100 customers on the system (2 feeders, 50 customers each)

50 customers had 12 momentary interruptions; the other 50 customers had 8 momentary interruptions. (1 breaker had 12 operations; 1 breaker had 8)

(50 x 12) + (50 x 8) = 600 + 400 = 1000 MAIFI = 1000 = 10.0

100


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MAIFI continued

MAIFI Two breaker operations followed by a

successful reclose: MAIFI=2

MAIFIE - event MAIFI Two breaker operations followed by a

successful reclose: MAIFIE =1


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Interesting (?) facts

Relationship between ASAI and SAIDI.

If you know one, you can calculate the other.

ASAI = Minutes per year – SAIDI min. Minutes per year


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Interesting (?) facts

If resources are unlimited, can you set a goal and successfully improve all your indices?

No… SAIDI = Customer Interruption Durations

Total number of customers served

SAIFI= Total Number of Customers Interrupted Total number of customers served


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SAIDI = Customer Interruption Durations SAIFI Total number of customers served Total Number of Customers Interrupted Total number of customers served

Customer Interruption Duration = CAIDI Total number of customers interrupted

CAIDI = SAIDI SAIFI

SAIFI goes down, CAIDI goes UP.


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Comparisons

Can you compare your utility’s reliability to those located a

few states away?


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Definitions

Standard definitions may not be the same as your utility’s definition or your neighbor’s definition.

Standard definitions may change or evolve over time.


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Loss of service

1998 definitionThe loss of electrical power, a complete loss of voltage to one or more customers.

2003 definitionA complete loss of voltage on at least one normally energized conductor to one or more customers.


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Distribution system

The distribution system is generally considered to be anything from the distribution substation fence to the customer meter. Often the initial overcurrent protection and voltage regulators are within the substation fence…

1998 - “period.” 2003 - and are considered to be part of the

distribution system.


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Number of customers

Is this the A) average number of customers during the

reporting period, or B) the number of customers at the end of

the reporting period? 1998 - total number at end 2003 - average number


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Momentary vs Sustained

Utilities commonly use one minute, three minutes, or five minutes.

IEEE has referenced five minutes since early days of the working group.

We always used one minute, but recently changed with 2003 standard.


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Variations

Level of automated data (connected OMS model vs. estimated customer count)

System design, geography, weather, maintenance, vegetation management...


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Exclusions

Interruptions that occur as a result of outages on customer-owned facilities or loss of supply from another utility. Substation/transmission - upstream of

defined distribution system. Data classification exclusions

(major events? planned interruptions?)


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Major Event Day

Major Storm has now been redefined as major event day (MED)

Large variation between companies on how to define a major storm. IEEE definitions changed over time and were often not specific.

The new method is a statistical approach using previous five years of data.

This has been considered by IEEE since 1992, but not incorporated into standard until 2003 version.


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Major Event Day

Allows major events to be studied separately. Better reveals trends in daily operation that

would be hidden by impact of major events. Old methods had difficulties in creating a

uniform list of types of major events. extensive mechanical damage; widespread damage catastrophic event named stormed; NWS reference 10% of customers interrupted

Understandable, easy to apply, specific, fair Exclusions are based on each utility’s recent past

performance.


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2.5 Beta Method

Based on the statistical principal of standard deviation ().

Beta is used because Natural log of data is

used Outage data only has

positive values.


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MED – 2.5 Beta

Daily SAIDI data for 5 yearsCluster plot


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MED – 2.5 Beta

Raw data and LN(data) - sorted


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MED – 2.5 Beta

LN(SAIDI) w/ “imaginary” component


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Specific MED exclusions

Day of Year

Average Customers

Customer Events

Customers Interrupted

Customer Mintues SAIDI Explanation

8/14/04 139838 1 80+ 65000 est. 12624618 90.2805 Hurricane Charley

8/29/04 139838 2 71 17196 2578012 18.4357 Hurricane Gaston

1/25/00 125894 3 48 6614 685353 5.4439 Snow storm J an 2000

7/6/01 129093 4 50 7083 509688 3.9482 Myrtle Beach Tornado

1/26/04 139838 5 37 6308 504828 3.6101 Ice Storm of J an 04

5/30/04 139838 6 16 3483 349126 2.4967 Wind related: Case 420740 and others: SRB, SRC, SRG, NCD

9/2/00 125894 7 7 1578 270180 2.1461 Dig-in on GBB: 1404 cust for 169 min; ACI excl, but it may have led to prolonged breaker outage.

8/30/04 139838 8 17 2025 261819 1.8723 The day after Hurricane Gaston (new or re-opened cases)

1/3/02 131765 9 90 6036 235566 1.7878 Ice/ Snow Tree/ NP (Many outages)

4/9/03 135132 10 5 3099 222092 1.6435 Case 313295 ODF, ODG and CGC

12/20/03 135132 11 9 3966 206439 1.5277 CHE CHG CHH and WME outages

12/14/01 129093 12 7 2607 187210 1.4502 Case 15079 - event where vandal opened East Conway breakers

7/20/02 131765 13 13 2749 186210 1.4132 RPC, SSF, WMG outages. Two due to lightning.

8/25/02 131765 14 23 1150 183229 1.3906 48E (lightning) and STD (wind)

7/2/01 129093 15 39 2542 177524 1.3752 Lightning - many small events and WME lockout ( case 12085)

1/24/03 135132 16 39 3582 166065 1.2289 Famous cold day: many outages. All-time peak load, 16 degrees


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Santee Cooper Reliability

We have been tracking reliability data since 1989

Early years used: Draft #2 of the IEEE working group (July 1992) IEEE 859-1987 – standard terms for reporting

transmission outages “Utilities need a standard measure of performance”

Electric World, Oct 1991 Internal opinion

Added to corporate goals (incentive) in 1996 Migrated to IEEE standard over time


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Santee Cooper data Date Time Area Circuit ID Equipment type Equipment # # of customers Minutes Customer-minutes Cause Outage (forced/planned) Isolating Equipment Damaged Equipment Type (OH/UG)

Case# Assigned To Assigned Time Repaired by Repaired Time Total customers Length of outage Customer outage time Transformer info Comments Repair Action Reliability Y/N


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Santee Cooper data


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OMS Improvement

More accurate customer counts Outage times tracked more accurately

grouping customers into outages restoration times for those outages

Accurate, real-time statistics Better data for reporting and decision making Reliability statistics may go down, although

“real” reliability should improve due to device prediction and efficient dispatch


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Monthly Reliability Report

Reliability Report for the Month of December 2004

TOTAL TOT CUST TOTAL SAIFI SAIDI TOTAL AVERAGETOTAL # OF CUSTS INTERRUPT INTERRUPT Actual Actual AVERAGE INTERRUPT

INTERRUPTS AFFECTED TIME DURATION (freq) (min) CAIDI CUSTS DURATION MAIFI ASAIALL DISTRIBUTION 1974 89453 3614920 120207 0.64 25.85 40.41 139838 60.90 10.39 99.9951%

ALL DISTRIBUTION (all events) 2450 131198 7188130 171970 0.94 51.40 54.79 139838 70.19 10.39 99.9902%

CON (year to date) 419 16727 905076 23530 0.90 48.62 54.11 18614 56.16 17.69 99.9908%

NMB (year to date) 376 22492 730548 22156 0.70 22.62 32.48 32291 58.93 9.56 99.9957%

MB (year to date) 519 28776 990535 30537 0.67 23.20 34.42 42701 58.84 8.31 99.9956%

GC (year to date) 418 16669 771413 28527 0.42 19.48 46.28 39600 68.25 9.14 99.9963%

BER (year to date) 242 4789 217348 15457 0.72 32.77 45.39 6632 63.87 14.84 99.9938%

MONTHLY FOR ALL DIST 97 5770 182759 6122 0.04 1.29 31.67 141521 63.11 0.37 99.9971%

MONTHLY FOR CONWAY 14 212 10591 783 0.01 0.56 49.96 18961 55.93 0.32 99.9987%

MONTHLY FOR NMB 27 2796 85563 1776 0.09 2.62 30.60 32675 65.78 0.44 99.9941%

MONTHLY FOR MB 23 1743 42317 1813 0.04 0.98 24.28 43061 78.83 0.26 99.9978%

MONTHLY FOR GC 19 396 31480 1099 0.01 0.79 79.50 40121 57.84 0.42 99.9982%

MONTHLY FOR BER 14 623 12808 651 0.09 1.91 20.56 6703 46.50 0.43 99.9957%


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ASAI Graph

ASAI for All Distribution for 2003

99.982

99.984

99.986

99.988

99.99

99.992

99.994

99.996

99.998

100

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Per

cent 2003 All Dist

2003 Con

2003 NMB

2003 MB

2003 GC

2003 Berk

Goal99.995%


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Animal Related Stats

2004 Animal Related Outages

0

5

10

15

20

25

BER CON MB NMB GC

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec


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Specific Analysis

Transformer fuse / Animal Analysis

0

100

200

300

400

500

600

700

800

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%

Number of animaloutages

Number of AnimalOutages whereTransformer Fusewas the IsolatingEquipmentPercentage


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Customer-Minutes per Failed Equipment


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Santee Cooper uses Target for Distribution Services within the Corporate

Goals program. (ASAI=99.995%) Line crew service centers have a target goal of outage

time not to exceed 68 minutes. MAIFI data is used for circuit patrol (>5). Composite index = (SAIDI) + (SAIFI) + (MAIFI) is used

to rank circuits for overhead and underground maintenance.

where = [weight, index, index target]

• Damage claim research.• Future uses will center around Reliability Planning where

more detailed analysis of circuits will recommend more specific actions for underperforming circuits.


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Adopt a standard

IEEE 1366 Other state or PUC standard may apply.

Helps maintain consistency and is based on best practices

Gives you “solid ground” to stand on when results and performance are questioned

Best chance in allowing you to compare yourself to other utilities.


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References

IEEE Std 1366-2003IEEE Guide for Electric Power Distribution Reliability Indices http://standards.ieee.org $63 ($52) softcover, $55 ($45) PDF

Electric Power Distribution Reliability, Richard Brown, ABB, Marcel Dekker Inc, 2002


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Reliability 101

Questions?

reliability 101 appa 2005 e&o technical conference memphis, tn april 19, 2005 gregg turbeville,...

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