Age Is A Poor Proxy Why relying on age-based replacement is imprudent Presented by Dan ONeill to the EUCI Aging T&D Infrastructure Workshop February 21,

Age Is A Poor ProxyAge Is A Poor Proxy

Why relying on age-based replacement is Why relying on age-based replacement is imprudentimprudent

Presented by Dan O’Neillto the

EUCI Aging T&D Infrastructure Workshop

Presented by Dan O’Neillto the

EUCI Aging T&D Infrastructure Workshop

February 21, 2001

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Number of states with new electric reliability rules

Source: Article by Navigant Consulting Inc.’s Dan O’Neill, Public Utilities Fortnightly, March 1999, updated

As public concern for reliability increases...As public concern for reliability increases...

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...Public cries to replace aging infrastructure increase...Public cries to replace aging infrastructure increase

July 15, 1999, Thursday Metropolitan Desk

And yesterday, Mr. Giuliani continued his attacks on Con Edison's response as too passive. ''What Con Edison should be saying is here are the things that have to be done to make it virtually impossible for blackouts to take place,'' he said. ''We need more power. We need to purchase more power. We need more alternatives. We need a more modern infrastructure, meaning we have to improve the feeder cables so we have better material. We need to insulate them better.''

(emphasis added)

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But if the public knew the facts about age & reliabilityThey would say that relying on age-based replacement is imprudentBut if the public knew the facts about age & reliabilityThey would say that relying on age-based replacement is imprudent

Not cost-effectiveNot cost-effectiveReplacing infrastructure components based on age is one of the least cost-effective ways of improving service

Not method-efficientNot method-efficientThere are better indicators of deterioration than age, e.g., specific failure history, test results, defective types

Not best practiceNot best practice

Other industries have learned not to rely on age for reliability management, e.g., aerospace, automotive, even natural gas pipelines and LDC’s

Relying on age-based replacement for reliability is

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Customer interruptions

Customer minutes

Restoration time

Device outages

Customers per deviceVegetation

Animal

Lightning

Equipment

Trim, remove, mow & spray

Guards, BIL

Arresters, BIL shield, ground

Inspect, repair/replace

OtherPlanning, upgrades

SAIDI / SAIFIWorst circuitsSatisfaction

Remediation Root cause

Effectiveness

$

Sectionalizing

Deployment

Asset management is key in the distribution business modelAsset management is key in the distribution business model

Accurate estimates

Know what you spend by program

Don’t spend money on the wrong problem

Don’t just assume 75% reduction

Minimize the impact of outages that remain

Make sure you are right-sized

Customers really want to know

Measure the right things

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Replacement is only one of the asset management strategiesAnd there are usually much better ways to improve customer service Replacement is only one of the asset management strategiesAnd there are usually much better ways to improve customer service

Asset Management Strategies

- Improved standards for new construction

- Preventive maintenance

- Remediation of failure-prone conditions

- Replacement of failure-prone components

- Re-design for redundancy

- Reinforce for capacity

- Inspection and condition monitoring

- Mitigation of effects on customer satisfaction

- Rapid repair and restoration

And it is not usually the most cost-effective...

…except when combined with inspection and monitoring to replace only just-in-time

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0

100

200

300

400

500

600

191

4

192

0

192

4

192

9

193

4

193

9

194

3

194

7

195

1

195

5

195

9

196

3

196

7

197

1

197

5

197

9

198

3

198

7

199

1

199

5

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

Cumulative Line Miles Line Miles Added

Cab

le M

iles

Ad

de

d b

y Y

ea

r Cum

ula

tive L

ine M

iles

‘Age’ is not the same as ‘vintage’ if the real issue is defectsManufacturing problems in certain ‘vintages’ are not really ‘age-based’‘Age’ is not the same as ‘vintage’ if the real issue is defectsManufacturing problems in certain ‘vintages’ are not really ‘age-based’

Certain early vintages of solid cable are known to be failure-prone

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Cable Failure

Improper Installation

Mechanical Damage

Mark-outs

Enforce Penalties

Temperature of cable

Manufacturer Defect

Insulation Breakdown

Dig In

Treeing

Rocky Soil

Enforce Trench

StandardsImproper Training

Insulation Thickness/Type

Cable Injection

Cable Replacement

Lightning

One Call

Upgrade to MOV

Arresters around open

New Construction

Jacket/casing missing/broke

Moisture in cable/joint

Rock Bruising

Corrosion Strength

Steam (Ducted)

LoadingVentilation(Ducted)

AddCapacity

Maintain Manholes

Capacity Planning

Thumping

Cathodic Protection

Maintain Cath Prot

Street Crossing

In root cause analysis, age is often a proxy for ‘cycles’In root cause analysis, age is often a proxy for ‘cycles’

Thermal Instability

Wet Manhole

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Exponential density functionMean = 15

0%

1%

2%

3%

4%

5%

6%

7%

0 5 10 15 20 25 30 35 40 45 50

Cycles to failure

Pro

bab

ility

of

failu

re

Many components’ failures fit the exponential process modelWhich means they are ‘memory-less’ and independent of ‘age’ or ‘cycles’Many components’ failures fit the exponential process modelWhich means they are ‘memory-less’ and independent of ‘age’ or ‘cycles’

So, for an exponential

process, preventive

replacement will not work at all, e.g., light bulbs

For the exponential curve, the slope at the origin

points to the mean

At any point on the curve, the mean ‘cycles to failure’

is the same

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This is This is typical for typical for

devices devices like circuit like circuit breakers, breakers, where the where the

‘cycles’ are ‘cycles’ are fault fault

operationsoperations

The Weibull curve assumes ‘wearout’ caused by cyclesWith a failure rate that increases with ‘age’ or ‘cycles’ The Weibull curve assumes ‘wearout’ caused by cyclesWith a failure rate that increases with ‘age’ or ‘cycles’

Weibull conditional failure ratemean = 15

0%

10%

20%

30%

40%

50%

60%

70%

80%

0 5 10 15 20 25 30 35 40 45 50

Cycles at failure

Fa

ilu

re r

ate

(fa

ilu

res

/ su

rviv

ors

)

shape = 2.5

shape = 1.0

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But for such components, overhaul often resets the ‘clock’Older devices may simply require fewer cycles between overhaulsBut for such components, overhaul often resets the ‘clock’Older devices may simply require fewer cycles between overhauls

Weibull conditional failure rateshape = 2.5

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

0 5 10 15 20 25 30 35

Cycles since last overhaul

Fa

ilu

re r

ate

(fa

ilu

res

/ su

rviv

ors

)

Older

Newer

Usually, the Usually, the real reason real reason to replace to replace

old devices old devices is due to is due to

economicseconomics, , not for not for

reliabilityreliability

An older device of this type can be maintained to

have the same rate of failure

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Minutes per outage

Growth rate of outages

Past outages per mile

Cost permile

The key to optimal replacement is high failure rateThe key to optimal replacement is high failure rate

Future minutes per year avoided

Dollars spent

Future minutesavoided per yearFuture outages

avoided per year

Future outagesavoided per year

Past outagesper year

Bang per buck

Past outages per year Miles of line

to be replaced

1 $90,000

1.25 45001 min.$2.00

Miles of line to be replaced

Dollars spent

8x x x =

Where:

• $90,000 per mile = 5280 feet/mile x $17 per foot to replace• 8 outages/mile/year = 13 spans/mile x (3 outages per 400ft span in past 5 years)• 25% growth rate = 3 outages in past 5 years becomes 3 outages in next 4 years• 4500 minutes per outage = 50 customers per outage x 90 minutes per outage

The higher the failure rate... …the higher the bang per buck

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0.000

0.100

0.200

0.300

0.400

0.500

0.600

0 5 10 15 20 25 30 35 40 45 50

Age of cable (years)

Ca

ble

fa

ilu

res

pe

r m

ile

Typically, age-based failure rates are still low (~ 50% above average)So age-based programs must replace a lot of good stuff to get the badTypically, age-based failure rates are still low (~ 50% above average)So age-based programs must replace a lot of good stuff to get the bad

Although a Although a failure rate failure rate difference difference

of 3x is of 3x is significant,ssignificant,s

ome ome conditions conditions

provide 10x, provide 10x, e.g., 250’ e.g., 250’

cable cable sections sections that have that have failed 3 failed 3

times in the times in the last 5 years last 5 years

fail at 6.0 fail at 6.0 per mile per mile

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Refocus on satisfactionRefocus on satisfaction Understand what aspects of reliability truly affect customer satisfaction, so that you can do the right thing and not just do things right

Re-design the systemRe-design the system Look for ways to cost-effectively re-design the system to build in redundancy and to mitigate effects through sectionalizing and auto-restore

Research root causesResearch root causesFind other conditions that are cost-effectively monitorable, and develop the predictive relationships that would allow more targeted action

Design solutionsDesign solutionsFind the best ways, including new ways, to remedy the root causes and to mitigate the effects, including faster restoration and informing customers

Prioritize the workPrioritize the workCompute the ‘bang per buck’ for each type of remediation, replacement, redesign, etc., then optimize and prioritize accordingly

Monitor the resultsMonitor the resultsMonitor the effectiveness of the programs to see what is really working and to discover any new insights that come only ‘after the smoke clears’

Here is a road map up to the ‘next level’Here is a road map up to the ‘next level’

There is a better way than aged-based replacementThere is a better way than aged-based replacement

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Taking reliability programs to the ‘next level’Taking reliability programs to the ‘next level’

Questions and answersQuestions and answers

DANIEL E. O’NEILL

Director, T&D Reliability & Operations Practice

Main: (781) 270-0101

Home Office: (404) 816-5647

Mobile: (404) 307-3661

Fax: (404) 841-9460

[email protected]

200 Wheeler Road, Suite 400

Burlington, MA 01803

1043 Lenox Crest NE

Atlanta, GA 30324