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Prague, 8-11 June 2009

Colin Gardner – United Kingdom

Use of diagnostic and condition assessment techniques for asset risk management

Colin GardnerHead of Asset Management

EDF Energy Networks



Contents

• Use of diagnostic techniques/condition monitoring for asset risk management

• Examples of techniques in use– Transformers– Switchgear– Overhead Lines– Underground Cables

• Summary

Scottish Power

CE ElectricENW

CE Electric

ScottishPower

WesternPowerDistribution

CentralNetworks

Scottish &Southern

Scottish &Southern

14.6 GW peakdemand

7.9 million homesand businesses



Condition monitoring and diagnostic testing context

Measure Process ActInterpret

MaintainReplaceDevelopRepair

Operate

Assess capacityRemnant life

ReliabilityPolicies

etc.

Condition monitoring

SenseObserveSample

On/off siteOn/off line

Continuous/testAll/sample

ModelsAlgorithms

Diagnostic testing Communication

Monitoring requirements



Condition based risk management

CombinedHealth Index

Future – withintervention

InterventionRepair

RefurbishReplace


Future – nointervention


Existing

DegradationFailure mech.Environment

Duty

Investmentplan

ExistingRisk

Future Riskno intervention

Future Riskwith intervention

Consequencesnetwork performance, safety, cost, environment

Criticality

Condition

Probabilityof failure



ASSET CONDITION CATEGORIES

• 4 point condition scoring: 1 as new, 4 end of life• Multiple condition points for each asset• Condition 3 triggers refurbishment if economic• Condition 4 triggers high volume asset replacement• Individual detailed assessment for high value assets • Type defects trigger additional condition monitoring



Health IndexYear 0 Health Index Profile

0

100

200

300

400

500

600

700

800

0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 10+ NoResult

Category

Num

ber o

f Ass

ets

Primary CB Distribution SG Distribution CB Other

Year 10 Health Index Profile

0

100

200

300

400

500

600

700

0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 10+ NoResult

Category

Num

ber o

f Ass

ets


% Replacement Intervention HI Profile at Year 10

0100200300400500600700

0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 10+ NoResult

Category

Num

ber o

f Ass

ets


Year 0 Year 10

Year 10 withreplacement

Health index shift



Asset RiskTotal Condition and Non-Condition Risk

0

200,000

400,000

600,000

800,000

1,000,000

1,200,000

1,400,000

1,600,000

Netw orkPerformance

Safety Opex Capex Environmental

Valu

e of

Ris

k

Year 0 Risk Profile Year 10 Risk Profile Year 10, % replacement

Year 10, Targeted Intervention Risk of New Assets



TRANSFORMERS

• Routine oil tests• On-line oil monitoring• Winding temperature

sensing• Thermal imaging• Tap changer operations

and motor current• Partial discharge• Bushing tests• External condition • Management systems



On line moistureremoval

Automatic breathers

Vacuumtap changer

On line gas and moisture monitorGood coatingsTemperature sensingOn line management systems

MEASURES TO MINIMISE MAINTENANCE AND EXTEND LIFE

Conservatorair bag



ROUTINE OIL SAMPLING:

Indicates the condition of core, winding and insulation

The routine tests comprise: • Dissolved gas analysis• Moisture content• Acidity• Breakdown voltage• Furan content• PCB content

Good condition Bad

Condition based on oil results

0

50

100

150

200

250

300

350

400

1 2 3 4Condition Code

Tran

sfor

mer

s



Actual Tap Position

Duke Street T1 132/11/11kV132kV Winding

11kV Winding 211kV Winding 1

ATM MO150 STATUS (ACTIVE/FAIL)

Tank Temp. °C

Highest Winding Hot-Spot Temp. °C132kV Winding Hot-Spot Temp. °C11kV Winding 1 Hot-Spot Temp. °C

11kV Winding 2 Hot-Spot Temp. °C

Winding Bubbling Temp. Margin °C

THERMAL INDICATIONS

TAP CHANGER TANK

MAIN TANKTop Tank Oil Temp. °C Hydran Level, Main tank (ppm) *

%RH Level

Winding Paper Moisture Content (ppm) *

Insulating Barrier Moisture Content (ppm) *

Hydran Level, Tap Changer Tank (ppm) *

Hydran Level, COOLING CIRCUIT (ppm) *

GAS & MOISTURE MEASUREMENTS

Cooling Efficiency Index *

DERIVED TRANSFORMER CONDITION

SCADA OPERATIONAL DISPLAY



Actual Tap Position

TC Tank Temp. °C

Highest Winding Hot-Spot Temp. °C132kV Winding Hot-Spot Temp. °C11kV Winding 1 Hot-Spot Temp. °C

11kV Winding 2 Hot-Spot Temp. °C

Short Term Average Differential °CLong Term Average Differential °C

Winding Bubbling Temp. Margin °C

THERMAL INDICATIONS

TAP CHANGER TANK

MAIN TANKTop Tank Oil Temp. °C

Hydran Level, Main tank (ppm)

Hydran Level Hourly Trend, Main tank (ppm)

%RH Level

Winding Paper Moisture Content (ppm)

Insulating Barrier Moisture Content (ppm)

Hydran Level, OLTC Selector (ppm)

Hydran Level, COOLING CIRCUIT RETURN (ppm)

GAS & MOISTURE MEASUREMENTS

Cumulative Aging (days)

Cooling Efficiency Index

DERIVED TRANSFORMER CONDITION

Cumulative Age (days)

TREND ANALYSIS Duke Street T1 132/11/11kV

TREND DISPLAYS…

Make use of comprehensive PI data analysis in PI ProcessBook

LONG TERM ASSET MANAGEMENT



SWITCHGEAR

• Partial Discharge– TEV, ultrasound, UHF

• Circuit breaker timing– Test– SCADA timing

• Fluid pressure and density

• Fluid tests• Contact wear• Thermal imaging• Protection and control

supervision



PARTIAL DISCHARGE DETECTION (Handheld)

• Detects Transient Earth Voltage using a contact probe and by monitoring airborne ultrasonic signals

• Simple to use: Red, Amber and Green indications

• Used during routine substation inspection

Ultra TEV PD Surveyor



PARTIAL DISCHARGE DETECTION (Monitoring)

• Continuous monitoring of switchgear where discharge has been detected by some other measure

• Remotely monitored plus local alarm • Software enables point of discharge to be located

PDM03: TEV MonitorASM: TEV & Ultrasonic Monitor



OVERHEAD LINES

• Helicopter and foot patrols

• High definition photography

• Thermal imaging• Conductor corrosion• Foundation corrosion• Residual strength

– Ultrasonic, wood poles– Sample mechanical tests



HIGH RESOLUTION PHOTOGRAPHS

20 to 40 photographs taken of each tower from a helicopter

Used for investment planning and procurement

Corroded Bracings

Frayed Earth Wire



Overhead Line Health Indices

Health indices show the condition of individual components.

Anti

Clim

bing

Gua

rd

Barb

ed W

ire

Barb

ed W

ire S

pace

rs

Conc

rete

Con

ditio

n

Whe

ther

Pai

nted

Pain

t Co

nditi

on

Safe

ty S

igns

Prop

erty

Pla

te

Num

ber

Plat

e

Circ

uit

ID P

late

s Le

ft c

ct

Tow

er L

egs

Step

Bol

ts

Brac

ings

Cros

sarm

s

Peak

Pain

twor

k

U b

olts

or

Tow

er a

ttac

hmen

ts

Shac

kles

or

Link

s

Eart

hwire

Sus

pens

ion

Clam

ps

Eart

hwire

Ten

sion

Cla

mps

Eart

hwire

Jum

per

Eart

hwire

Bon

ds

Dam

pers

U b

olts

or

Tow

er a

ttac

hmen

ts

Shac

kles

and

Lin

ks

Insu

lato

rs

Arci

ng H

orns

Cond

ucto

r Su

spen

sion

Cla

mps

Cond

ucto

r Te

nsio

n Cl

amps

Vibr

atio

n D

ampe

rs

Cond

ucto

rs a

t cl

amps

Jum

pers

3 3 4 u u u 1 1 1 3 3 3 4 3 3 4 2 3 3 u 2 3 4 1 4 4 3 1

3 3 3 4 y 3 1 1 1 m 3 3 4 3 3 4 2 2 2 1 2 3 4 1 m 4 2 1

3 3 3 u u u 1 1 1 1 3 3 3 3 3 4 3 3 2 1 3 3 4 1 4 4 3 1

3 3 2 4 y 2 1 1 1 1 3 3 3 3 3 4 2 3 2 1 2 3 4 1 4 4 2 1

3 3 3 4 y 2 1 1 u 1 3 3 3 3 4 4 2 2 2 1 2 4 4 1 4 4 3 1

3 2 4 3 y 2 1 1 u 1 2 2 3 3 3 4 2 u u u 2 3 4 1 4 4 3 1

4 2 2 u u u 1 1 1 1 2 2 2 3 3 4 u u 1 1 1 2 u u 1 2 2 3 1 1

3 3 3 u u u 1 1 u 1 3 3 3 3 3 4 u u u u 2 u 4 1 4 4 2 u

3 2 2 u u u 1 1 u 1 3 3 3 3 3 4 u u u u 2 u 4 1 4 4 2 u

ACD Muffs Signs Tower Steelwork Earthwire Insulators And Fittings



UNDERGROUND CABLES

• Partial discharge mapping (on/off line)

• Fluid pressure• PFT fluid leak detection• Distributed Temperature

Sensing • Cable and joint sample

assessments



PARTIAL DISCHARGE MONITORING EQUIPMENT – MV Cables

ON-LINE CONDITION MONITORING

ANALYSIS: WEB INTERFACE



AVOIDANCE OF AN MV CABLE FAULT

Location (meters)1,0009008007006005004003002001000

All P

hase

s PD

2,000

1,800

1,600

1,400

1,200

1,000

800

600

400

200

0

Location of discharge

ON-LINE MAPPING

OFF-LINE MAPPING

Location of discharge

STAGE 1: On-line monitoring

0m154 442 840 904 1009m

0.3 Cu 300 CAS 0.3 Cu 0.3 Cu 300 CAS 0.3 CuCHATAM

WESTPrimary

South Hill

OVERLAY

DISCHARGING AREA

INCREASING PD ACTIVITY

NO DISCHARGES FOLLOWING RE-ENERGISATIONCABLE ANALYSIS



FLUID FILLED CABLES (FFC)

• Approximately 2,500km of fluid-filled cable, containing approximately 27 million litres of fluid

• Over 50% of the London HV network is FFC

• Most cables installed in the 1960s, some date back to 1930s

• Risk based repair and replacement based on

– Environmental sensitivity– Condition and criticality– Leak detection techniques



FFC ENVIRONMENTAL RISK ASSESSMENT

Legend • Purple – Very

High Risk• Red – High

Risk• Orange –

Medium Risk• Yellow – Low

& Risk



FFC CIRCUIT CLASSIFICATION

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

90.00

100.00

0.00 10.00 20.00 30.00 40.00 50.00 60.00

Environmental sensitivity

Con

ditio

n/ac

cess

ibili

ty/F

luid

loss



FLUID FILLED CABLES: CABLE PRESSURE MONITORING

WINTER

SUMMER

LOSS OF PRESSURE DUE

TO OIL LEAK



Reduced leakage, repairs and replacement

PerFluorocarbon Tracer CABLE LEAK LOCATION



Summary

• A range of techniques developed – some on line some stand alone

• New equipment specified to enable diagnostic testing/condition monitoring

• Essential support for asset risk management• Need to develop fully integrated approach• Key component of Smart Grids

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