TCATCA®®

Transformer Condition Transformer Condition AssessmentAssessment

TCA®® -Transformer Condition Assessment

TCA®® -Transformer Condition Assessment

�Provides�Provides

� Incipient Fault Information

�Mechanical Withstand Information

�Dielectric Withstand Information

�Moisture Dynamics Information

Development of TCADevelopment of TCA®®(Transformer Condition Assessment)(Transformer Condition Assessment)

�Driving Forces

�Successes with BOA®® and TASA®®

�Assess transformers position in it’s life cycle

� Need to get more out of our transformers

IntroductionIntroduction

�� A Huge Transformer Population has A Huge Transformer Population has Already been in Service for 25Already been in Service for 25--40 Years40 Years

�� The Fundamental Objective of The Fundamental Objective of Transformer Life Management is Transformer Life Management is The Fundamental Objective of The Fundamental Objective of Transformer Life Management is Transformer Life Management is Defined Simply as “Getting the Most Defined Simply as “Getting the Most Out of the Asset”Out of the Asset”

�� Transformer Fluids Contain About 70% Transformer Fluids Contain About 70% of the Available Diagnostic Information of the Available Diagnostic Information for Transformersfor Transformers

Introduction (Cont.)Introduction (Cont.)

�� Demand for electricity in most markets Demand for electricity in most markets is increasing by 2is increasing by 2--7% each year.7% each year.

�� Competition is forcing power companies Competition is forcing power companies to postpone new investments and to postpone new investments and Competition is forcing power companies Competition is forcing power companies to postpone new investments and to postpone new investments and achieve as much as possible with achieve as much as possible with existing assets.existing assets.

�� Today, average load on transformers is Today, average load on transformers is typically 80typically 80--100%, compared with 60% 100%, compared with 60% a few decades ago.a few decades ago.

CH2OH

C O

H

C C

CH2OH

C O

H O

C C

H OH

C C

OH H H

C C

CelluloseCellulose

OH H H

C C

H OH

OH H H

C C

H OH

H O

C O

CH2OH

Paper insulation is a polymer consisting of repeating D-Glucose units held together in long chains. The number of repeating units is referred to as the Degree of Polymerization or DP

Degree of Polymerization (DP)Degree of Polymerization (DP)

•• Dielectric strength does not decrease with Dielectric strength does not decrease with agingaging

•• Paper Paper aging is associated with aging is associated with loss loss ofofmechanical strengthmechanical strengthmechanical strengthmechanical strength

•• The stress from short circuits can lead to The stress from short circuits can lead to failurefailure

•• DP in new units will vary between 800 DP in new units will vary between 800 --12001200

•• A DP of 200 indicates end of lifeA DP of 200 indicates end of life

Key Fault GasesKey Fault GasesFrom CelluloseFrom Cellulose

Low TemperatureLow Temperature Carbon DioxideCarbon DioxideLow TemperatureLow Temperature

High TemperatureHigh Temperature

Carbon DioxideCarbon Dioxide

Carbon Dioxide with Carbon Dioxide with Carbon MonoxideCarbon Monoxide

3 Processes of Paper 3 Processes of Paper DegradationDegradation

�� PyrolysisPyrolysis

�� OxidationOxidation�� OxidationOxidation

�� HydrolysisHydrolysis

Temperature effect on paperTemperature effect on paper�� For every 6 deg rise, the life of cellulose is For every 6 deg rise, the life of cellulose is

halved.halved.

A g e in g R a te

98 1049286 110

0 .25

0 .50

1 .00

2 .00

°C

A g e in g R a te

H o t S po t T em p era tu re θh °C

4 .00

Pyrolysis of Cellulose

Cellulose Glucose + H2O + CO + CO2 + RCOOH(Acid)

Thermal Load is proportional to life

Oxidation of Cellulose

O2Cellulose RCOOH + RCOH + H2O

(Acid) (alc.+ald.)

O2

CH2OH

C O

H

C C

CH2OH

C O

H O

C C

H OH

C C

OH H H

C C

Hydrolysis of Cellulose

OH H H

C C

H OH

OH H H

C C

H OH

H O

C O

CH2OH

H H

O

Monitoring Paper ConditionMonitoring Paper Condition

�� Take paper sampleTake paper sample

�� DGA DGA –– look at carbon gas levels & look at carbon gas levels & �� DGA DGA –– look at carbon gas levels & look at carbon gas levels & ratiosratios

�� Measure furans in oilMeasure furans in oil

Sample Identification

Layer Degree of polymerisation

1 250 2 297 3 301 4 321 Outer Winding 5 342

Sample Identification

Layer Degree of polymerisation

1 261 2 304 3 319 4 321 Outer Winding 5 337

DP Paper Test Results

Outer Winding 5 342 6 324 7 351 8 368 9 396 10 411

Outer Winding 5 337 Under Clamp 6 351

7 385 8 376 9 398 10 425

WATER DISTRIBUTION BETWEEN

CELLULOSE-MINERAL OIL

4

5

WA

TE

R IN

PA

PE

R(%

)

0

1

2

3

0 10 20 30 40 50 60 70 80 90

WATER IN OIL (PPM)

WA

TE

R IN

PA

PE

R(%

)

100OC

Managing MoistureManaging Moisture--inin--paperpaper

Moisture in Moisture in paper (% by wt)paper (% by wt)

Recommended ActionRecommended Action

≤≤ 0.5%0.5% No action required. Paper relatively dry.No action required. Paper relatively dry.

1% to 2%1% to 2% Correlate with transformer’s age, loading history, Correlate with transformer’s age, loading history, 1% to 2%1% to 2% Correlate with transformer’s age, loading history, Correlate with transformer’s age, loading history, external moisture ingress, maint of breathing system.external moisture ingress, maint of breathing system.

2% to 3%2% to 3% Start planning suitable period for dryStart planning suitable period for dry--out.out.

3% to 4%3% to 4% Paper insulation system in need of drying.Paper insulation system in need of drying.

> 4%> 4% Risk of internal flashovers. Insulation resistance of Risk of internal flashovers. Insulation resistance of paper can fall and lead to gassing problems.paper can fall and lead to gassing problems.

TCATCA®® Case StudyCase StudyDissolved Gas AnalysisDissolved Gas Analysis

Gas Test 1 Test 2 ppm ppm

Hydrogen 3246 4098 Methane 15941 21396

Ethane 4115 4860

Ethylene 27293 34664

Acetylene 168 247

Carbon Monoxide 187 251

Carbon Dioxide 6299 8158

TCA code 4*

TCATCA®® Case StudyCase StudyParticle Count Test DataParticle Count Test Data

Particle Size microns

Test 1 Count

Test 2 Count

5 to 15 9275 144800

15 to 25 1685 17450 15 to 25 1685 17450

25 to 50 780 3725

50 to 100 140 170

> 100 15 10

TCA code 4*TCA code 4*

TCATCA®® Case StudyCase StudyDiagnostic IndicationsDiagnostic Indications

�� Severe HeatingSevere Heating

�� Possible CokingPossible Coking�� Possible CokingPossible Coking

�� Arcing at a connector or contactArcing at a connector or contact

�� Activity adjacent to but not directly in Activity adjacent to but not directly in contact with cellulose.contact with cellulose.

TCATCA®® Case StudyCase Study

Gas 17/12/99 20/9/02 Ppm ppm

Hydrogen 1 68 Methane 1 9

Ethane 2 0 Ethane 2 0

Ethylene 0

0

Acetylene 0 0

Carbon Monoxide 27 689

Carbon Dioxide 540 34484 Nitrogen 60059 65558

Oxygen 2385 3414

Particle Size microns

17/12/99 Count

20/09/02 Count

5 to 15 18530 100385

15 to 25 1770 6645

TCATCA®® Case StudyCase Study

15 to 25 1770 6645

25 to 50 460 1155

50 to 100 65 40

> 100 0 0

17/12/99 ppm

20/09/02 ppm

HMF ND 0.052

FAL ND 1.105

TCATCA®® Case StudyCase Study

FAL ND 1.105

ACF ND 0.021

MEF ND 0.062

FOL ND 0.811

Est. DP >1000 342 - 419

17-Dec-99 20-Dec-02

Moisture 11 59 ppm

D1816 32 12 kV

TCATCA®® Case StudyCase Study

D1816 32 12 kV

Acid No. 0.008 0.066 mg KOH/g

IFT 37.0 36.3 Dynes/cm

Color <1.5 <1.5

D924 @ 25C 0.017 0.44

Ox. Inh. 0.062 0.113 %

Bubble Emission

TCATCA®® Case StudyCase StudySNOWY HYDRO (NSW)SNOWY HYDRO (NSW)

�� CASE STUDYCASE STUDY

�� 88/176 MVA TRANSFORMER88/176 MVA TRANSFORMER

�� MADE BY TYREE (MOOREBANK)MADE BY TYREE (MOOREBANK)�� MADE BY TYREE (MOOREBANK)MADE BY TYREE (MOOREBANK)

�� 1 OF 3 SISTER UNITS 1 OF 3 SISTER UNITS OPERATING AT TUMUT 3 OPERATING AT TUMUT 3 POWER STATIONPOWER STATION

May-03 Oct-03 Nov-03 Hydrogen 190 270 232 Methane 305 349 763 Ethane 42 88 195

Fault ProgressionFault Progression

42 88 195 Ethylene 100 218 939 Acetylene 1 8 53 Carbon Monoxide 61 299 665 Carbon Dioxide 2641 3600 3859

Effect of Temperature on Effect of Temperature on Distribution of GasesDistribution of Gases

H

CH

C H

C H

C H

CO

CO

O

NH2

ppm

CH4

ppm C2H4

ppm C2H2

ppm C2H6

ppm CO ppm

CO2

ppm O2

% N2

%

20 °C, before heating trace 172 78 ND 56 923 1929 0.08 2.9

64 °C, after heating 56 269 147 1.3 90 1163 2654 0.09 5.5

GSU TRANSFORMERGSU TRANSFORMER

��240 MVA, 16/275 kV240 MVA, 16/275 kV

��High speed ResistorHigh speed Resistor--type OLTC (32 type OLTC (32 type OLTC (32 type OLTC (32 steps)steps)

OIL ANALYSISOIL ANALYSIS

�� Methane, Ethane and Methane, Ethane and Ethylene increased over Ethylene increased over an 18 month periodan 18 month period

�� Analysis indicated a Analysis indicated a heating problem >700 heating problem >700 heating problem >700 heating problem >700 degCdegC

�� Rises in gas levels were Rises in gas levels were neitherneither sudden or severe, sudden or severe, so the transformer was so the transformer was closely monitored and oil closely monitored and oil samples tested each samples tested each month.month.

ACETYLENEACETYLENE

�� JunJun--08: Heating 08: Heating problem had problem had developed into developed into arcingarcingHot joint in the Tap Hot joint in the Tap ��Hot joint in the Tap Hot joint in the Tap Changer Selector Changer Selector Switch was Switch was suspected causesuspected cause

��Removed from Removed from service to inspectservice to inspect

ASEA Tap ChangerASEA Tap Changer

�� 2 parts: Diverter Switch 2 parts: Diverter Switch mounted above a mounted above a Selector Switch (oil Selector Switch (oil separate)separate)

�� Current switching and Current switching and �� Current switching and Current switching and arcing occurs in the arcing occurs in the Diverter Switch tank. Diverter Switch tank. Then while the current is Then while the current is diverted through resistors diverted through resistors the Tap Selector Switch the Tap Selector Switch moves tap position.moves tap position.

As Found …As Found …�� Burnt, carbonised Burnt, carbonised

contacts on Fixed & contacts on Fixed & Moving Contacts of Tap Moving Contacts of Tap Selector Selector

Arcing damage on Fixed Contact

Arcing damage on Moving Contact

Transformer Failure!!Transformer Failure!!500/230 kV Single Phase (Transmission)500/230 kV Single Phase (Transmission)

Dissolved Gas Analysis

Gas ppm

H2 6043CH4 7378CH4 7378

C2H6 785C2H4 4383C2H2 1938

CO 1473CO2 137

N2 18040O2 4350

Pyrolysis of Cellulose

Case 7

Figure 1

TransformerTransformer FailureFailure

Figure 2

TransformerTransformer FailureFailure

Figure 3

TransformerTransformer FailureFailure

Figure 4

Transformer FailureTransformer Failure

Figure 5

TransformerTransformer FailureFailure

Figure 6

TransformerTransformer FailureFailure

Figure 8

Excitation TX1

Excitation TX2

Excitation TX3

Excitation TX4

Hydrogen <10 <10 <10 <10

Methane 5 3 2 2

Ethane <1 <1 <1 1

Case Case Study 1:Study 1: NN22/O/O22 RatioRatio

Ethane <1 <1 <1 1

Ethylene <1 <1 <1 3

Acetylene <1 <1 <1 <1

Carbon Monoxide 24 19 15 125

Carbon Dioxide 180 170 130 835

Oxygen 820 1310 1520 23200

Nitrogen 59650 76920 67800 57650

N2/O2 Ratio 72:1 59:1 45:1 2.5:1

Transformer Transformer --suspected faultsuspected fault66/11 kV 10 MVA 196466/11 kV 10 MVA 1964

�� Sequence of events June/July 2000Sequence of events June/July 2000

�� 29/6 29/6 -- 3 phase pothead fault3 phase pothead fault

�� fault cleared, transformer refault cleared, transformer re--energisedenergised�� fault cleared, transformer refault cleared, transformer re--energisedenergisedand placed on loadand placed on load

�� less than 1 hour later, gas less than 1 hour later, gas buchholzbuchholzalarmalarm

�� transformer removed from servicetransformer removed from service

Transformer Transformer --suspected faultsuspected fault66/11 kV 10 MVA 196466/11 kV 10 MVA 1964

�� Number of tests undertakenNumber of tests undertaken

�� inconclusive inconclusive -- no fault indicatedno fault indicated

�� transformer retransformer re--energised off load for energised off load for �� transformer retransformer re--energised off load for energised off load for three days three days -- no problemsno problems

�� placed on loadplaced on load

�� one hour later one hour later -- gas buchholz alarmgas buchholz alarm

Example Example -- TransformerTransformer66/11 kV 10 MVA66/11 kV 10 MVAConservator, ONANConservator, ONAN

Key Gases ppm Nov-97 Jul-00

Hydrogen 57 2,222 Methane 3 871 Methane 3 871 Ethane 1 42 Ethylene 7 1,044 Acetylene 17 3,300 Carbon Monoxide 454 824 Carbon Dioxide 5,280 6,253 Oxygen 24,700 17,710 Nitrogen 68,800 65,030

What a Transformer Oil Testing What a Transformer Oil Testing Program is Capable of DetectingProgram is Capable of Detecting

* Abnormal Ageing * Deterioration of cellulose * Abnormal Ageing * Deterioration of cellulose

* Accumulation of Deposits insulation* Accumulation of Deposits insulation

* Internal Short * Failure of Cooling Fans* Internal Short * Failure of Cooling Fans

* Loose bushing connections * Hot Spots* Loose bushing connections * Hot Spots

* Contaminants in oil * Inadequate Cooling* Contaminants in oil * Inadequate Cooling

* Core overheating * Inadequate Cooling* Core overheating * Inadequate Cooling

* Corona or Partial Discharge * Internal Cooling* Corona or Partial Discharge * Internal Cooling

* Loose contacts * Loose connections* Loose contacts * Loose connections

* Detection or clogged radiators * OLTC contact * Detection or clogged radiators * OLTC contact

misalignmentmisalignment

What a Transformer Oil Testing What a Transformer Oil Testing Program is Capable of DetectingProgram is Capable of Detecting

* Localised overheating * Metals* Localised overheating * Metals--inin--oil oil

* Moisture in Oil* Moisture in Oil * Overheated conductors* Overheated conductors

* Overloading* Overloading * Oil quality* Oil quality* Overloading* Overloading * Oil quality* Oil quality

* Internal rust* Internal rust * Sludging of oil/windings* Sludging of oil/windings

* Blocking of cooling ducts* Blocking of cooling ducts * Unintentional core grounds* Unintentional core grounds

* Windings overheated* Windings overheated

BOABOA®® -- TASATASA®® -- TCATCA®®WillWill

� Identify�Potential failures due to operating practices

�Excessive load�Excessive load

�Load carrying deficiencies of components

�Potential failures due to maintenance practices

�Potential failures due to fault activity/exposure

SummarySummary

�� ConditionCondition--based maintenance of based maintenance of OCBsOCBs,, LTCsLTCs & transformers& transformers is possibleis possible

�� Diagnostic tests lead to condition Diagnostic tests lead to condition codescodescodescodes

�� Condition codes help to justify Condition codes help to justify maintenancemaintenance

�� Condition codes help to prioritize Condition codes help to prioritize maintenancemaintenance

�� Diagnostic programs lead to Diagnostic programs lead to enhancements in safety & reliabilityenhancements in safety & reliability