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Slide No. 1 Copyrights © 2005 TNB Research

UNDERSTANDING IEC 60599 : GUIDE

TO INTERPRETATION OF DISSOLVED

AND FREE GASES ANALYSIS

GOMATHY SETHURAMAN

TRANFORMER OIL

TESTING LABORATORY

29TH NOVEMBER 2007

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IEC 60599 : INTERPRETATION OF DGA

PRESENTATION OUTLINE

SCOPE OF IEC 60599

TRANFORMER OIL

CELLULOSE / PRESSBOARD SOLID INSULATION

MECHANISM OF GAS FORMATION

TYPE OF FAULTS vs TYPE OF GASES

DGA INTERPRETATION TABLE

CELLULOSE INSULATION DEGRADATION

IEEE DGA CONCENTRATION LIMIT

CASE STUDY

Gomathy Sethuraman TNBR

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SCOPE OF IEC 50699

• Dissolved and free gas analysis (DGA) is one of the most widely used

diagnostic tools for detecting and evaluating faults in electrical equipment.

• This guide is applicable to electrical equipment filled with mineral

insulating oil and insulated with cellulose or pressboard-base solid

insulation.

• This guide facilitates the DGA interpretation describing how the

concentration of DGA or free gases may be interpreted to diagnose the

condition of the oil-filled electrical equipment in service and suggest future

action.

* Terms and conditions apply - In any case, the indication should be viewed only as a

guidance and any resulting action should be undertaken only with proper

engineering judgment.



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TRANSFORMER OIL

CnH2n+2

• Composition of Mineral Transformer Oil

• Mixture of hydrocarbon compounds

» Naphthenic – 5, 6 or 7 carbon bonded in ring form

» Paraffin – carbon in straight chain

» Aromatic – 6 carbon bonded in ring form

» Heterocyclic – contains nitrogen, sulphur and oxygen



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CELLULOSE / PRESSBOARD SOLID INSULATION

(C6H10O5)n


n • Composition of Cellulose Insulation

• It’s a organic compound with carbon,

hydrogen and oxygen molecules

» Plant origin

» Polymerization of glucose

molecules


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MECHANISM OF GAS FORMATION


Oil

Decomposition

Cellulose

Decomposition

Other

Source

Heat Oxygen

Partial Discharge Thermal Fault

Arching Acid

Moisture

PARAMETERS THAT AFFECT OIL DEGRADATION

GASES PRODUCED

Nitrogen Oxygen Hydrogen Carbon Dioxide

Methane Acetylene Ethane Ethylene Carbon Monoxide


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TYPE OF FAULTS IN TRANSFORMER


Type Fault Examples

PD Partial

Discharge

Corona - resulting in X-wax deposition on paper

Sparking - resulting in pinhole, carbonized punctures on

paper

D1 Discharge of

low energy

In oil / paper - resulting in larger carbonized punctures,

tracking or carbon particles in oil

D2 Discharge of

high energy

In oil / paper - extensive destruction and carbonization of

paper, metal fusion (in some case tripping)

T1 Thermal Fault

TC < 300C

In oil / paper - colour of the insulation has turn brown

T2 Thermal Fault

300C < TC < 700C

In oil / paper - colour of the insulation has turn brown

and very obvious carbonization

T3 Thermal Fault

T > 700C

In oil / paper - strong evidence of carbonization, metal

coloration or metal fusion.


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TYPE OF FAULTS vs TYPE OF GASES


Type of Fault Source Gases produced

Corona Oil H2

Cellulose H2, CO, CO

2

Pyrolysis or

Over heating

Low Temperature

Oil CH4 , C

2H

6

Cellulose CO2 ( CO )

Pyrolysis or

Over heating

High Temperature

Oil C2H

4 , H

2 ( CH

4 , C

2H

6 )

Cellulose CO ( CO2 )

Arching Oil H

2, C

2H

2 (CH

4, C

2H

6, C

2H

4)


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DGA INTERPRETATION TABLE


CASE Characteristic Fault

C2H2

----------

C2H4

CH4

----------

H2

C2H4

----------

C2H6

PD Partial Discharge NS 1) < 0.1 < 0.2

D1 Discharge of low energy > 1 0.1 - 0.5 > 1

D2 Discharge of high energy 0.6 – 2.5 0.1 - 1 > 2

T1 Thermal fault TC < 300 C NS > 1 but NS < 1

T2 Thermal fault 300C < TC <

700C

< 0.1 > 1 1 - 4

T3 Thermal fault T > 700C < 0.2 2) > 1 > 4

1) NS = Non – significant whatever the value 2) An increase value of the amount of C2H2 may indicate that the hot spot

temperature is higher than 1000 C


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• Breakdown of cellulose insulation produce CO and CO2

• Extreme ratios of CO2/CO should be considered as unusual behaviour

©aizam

Diagnosis Interpretation

CO2

----------

CO

Overheating of the cellulose paper winding > 10

Degradation of cellulose caused by an electrical fault < 3 1) 2)

CELLULOSE INSULATION DEGRADATION


1) Ratio less than 3 (CO2/CO) are generally considered as an indication of

probable paper involvement in a fault 2) When excessive paper degradation is suspected, it is advised to ask for a

furanic compound test


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IEEE DGA CONCENTRATION LIMIT


Gases Generated Normal Caution Warning

Hydrogen (H2) 100 101 – 700 700

Acetylene (C2H

2) 35 36 – 45 45

Ethylene (C2H

4) 50 51 - 100 100

Ethane (C2H

6) 65 66 - 100 100

Methane (CH4) 120 121 - 400 400

Carbon Monoxide (CO) 350 351 - 570 570

Carbon Dioxide (CO2) 5000 5000 - 10000 10000


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CSI OF TRANSFORMER OIL ?

Failure Investigation Project

1. TRANSFORMER OIL : CASE STUDY A

2. TRANSFORMER OIL : CASE STUDY B

3. TRANSFORMER OIL : CASE STUDY C

Executive Summary :

A number of failed instruments were brought to TNB Research

to be analyzed for the cause of failure.

The failed instruments were subjected to • Electrical tests at the High Voltage Laboratory

• Oil test at the Transformer Oil Testing Laboratory

• Material and Visual test at the Advance Material Laboratory



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TEST DETAILS : FAILURE CASES

List of Test

1) Colour (ASTM 1500)

2) Density (ASTM D 4052)

3) Dielectric Breakdown (IEC 156)

4) Dissolved Gas Analysis (IEC 567)

5) Moisture Content (IEC 814)

6) Neutralization Value (IEC 296)

7) Dissipation Factor (IEC 247)

8) Interfacial Tension (ASTM D 971 – 99a)

9) Kinematic Viscosity 40 °C (ASTM D 445)

10) Carbon type (ASTM 2140)

NOTE :

1) Three samples were taken from each failed unit.

2) All three samples were tested individually based on the International Testing Method

3) Test were conducted under the transformer oil testing guidelines / settings

4) Interpretation of test results are based on IEC 60422 and IEC 60599



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PROPERTY TEST

Average

(3 Samples)

LIMIT (IEC 422)

Transformer Oil

1 Colour L 1.5 1.0 – 2.5

2 Density 0.8881 0.895 (max)

3 Dielectric

Breakdown 21.7 30kV (min)

4 Moisture

Content 112 30 (max)

5 Neutralization

Value 0.14 0.3 (max)

6 Dissipation Factor

(Tan Delta) 0.0069 0.03 (max)

7 Interfacial

Tension 15 24 (min)

8 Kinematic Viscosity 19.3 <11

9 Carbon Type Cp > Cn Cn > Cp

REMARK EVALUATION

GOOD •Oil does not meet the required limits of IEC 422

•High concentration moisture → Low BDV value

•Low IFT value → Presence of contamination

•High Viscosity → Poor heat insulation

NORMAL

LOW

HIGH

NORMAL

NORMAL

LOW

HIGH

Cp > Cn

CASE STUDY A



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DISSOLVED GAS ANALYSIS

AVERAGE LIMIT (IEC 60599)

Transformer Oil

Hydrogen 260 300

Oxygen 7173 -

Nitrogen 46243 -

Methane 69 30

Carbon Monoxide 65 300

Carbon Dioxide 3796 900

Ethylene 30 10

Ethane 318 50

Acetylene 2 2

REMARK EVALUATION

NORMAL • High

concentration

Ethane

Methane

Ethylene

→ Overheating

Carbon dioxide

→ Cellulose /

Paper Insulation

Degradation

-

-

High

NORMAL

High

High

High

NORMAL


CASE STUDY A


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Visible sludge and moisture


CASE STUDY A


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Sludge Contaminant


CASE STUDY A


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Overheating

burn mark

Rust mark due

to moisture


CASE STUDY A


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Overheating

burn mark

Overheating

marks


CASE STUDY A


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TEST Average LIMIT (IEC 422)

Transformer Oil

1 Colour L 1.5 1.0 – 2.5

2 Density (g/cm3) 0.8722 0.895 (max)

3 Dielectric

Breakdown (kV) 9 30kV (min)

4

A Dissolved Moisture

Content (ppm) 54

30 (max)

B Emulsified Moisture

Content (ppm) 393

5 Neutralization

Value( mgKOH/g) 0.03 0.3 (max)


(Tan Delta) 0.0081 0.03 (max)

REMARK EVALUATION

GOOD

•High concentration of moisture →

Low BDV value

NORMAL

LOW

HIGH

NORMAL

NORMAL


CASE STUDY B


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Transformer Oil

Hydrogen 8 300

Oxygen 46228 -

Nitrogen 80877 -

Methane 4 30



Ethylene 3 10

Ethane 20 50

Acetylene ND 2

REMARK EVALUATION

Normal

• High

concentration

Carbon dioxide

→ Overheating

→ Cellulose /

Paper Insulation

Degradation

-

-

Normal

Normal

High

Normal

Normal

Normal


CASE STUDY B


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Visible sludge and moisture


CASE STUDY B


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Contaminant Overheating

burn mark


CASE STUDY B


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Overheating burn mark


CASE STUDY B


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TEST Average LIMIT (IEC 422)

Transformer Oil

1 Colour L 1.5 1.0 – 2.5

2 Density (g/cm3) 0.8739 0.895 (max)

3 Dielectric

Breakdown (kV) 9 30kV (min)

4

A Dissolved Moisture

Content (ppm) 61

30 (max)

B Emulsified Moisture

Content (ppm) 613

5 Neutralization

Value( mgKOH/g) 0.035 0.3 (max)


(Tan Delta) 0.0075 0.03 (max)

REMARK EVALUATION

GOOD

•High concentration moisture → Low BDV value

•Two types of moisture

→ Dissolved

→ Emulsified

NORMAL

LOW

HIGH

NORMAL

NORMAL


CASE STUDY C


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Transformer Oil

Hydrogen 12.5 300

Oxygen 42564 -

Nitrogen 75302 -

Methane 4 30



Ethylene 4 10

Ethane 27 50

Acetylene ND 2

REMARK EVALUATION

Normal

• High

concentration

Carbon dioxide

→ Overheating

→ Cellulose /

Paper Insulation

Degradation

-

-

Normal

Normal

High

Normal

Normal

Normal


CASE STUDY C


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Visible sludge

and moisture Contamination


CASE STUDY C


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Overheating / burn mark on the cellulose / paper insulation


CASE STUDY C


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Contaminant Overheating

burn mark


CASE STUDY C


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CONCLUSION


Faults often start as incipient faults of low energy, which may develop

into more serious ones of higher energies, leading to possible gas alarms,

breakdowns and failures.

When a fault is detected at any stage of development, it may be quite

informative to examine not only the increase in gas concentration, but also

the possible evolution with time towards a more dangerous high-energy

fault

The RELIABILITY of a TRANSFORMER OIL depends on the BASIC

CHARACTER of the oil

BETTER THE OIL → BETTER THE PERFORMANCE

The RELIABILITY of a TRANSFORMER very much depends on the

BASIC CONDITION MONITORING of the oil

BETTER THE MONITORING → BETTER THE RELIABILITY


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