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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 DischargeThermal Fault
ArchingAcid
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
TC < 300C
In oil / paper - colour of the insulation has turn brown
T2 Thermal Fault
300C < TC < 700C
In oil / paper - colour of the insulation has turn brown
and very obvious carbonization
T3 Thermal Fault
T > 700C
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, CO2
Pyrolysis or
Over heating
Low Temperature
Oil CH4 , C2H6
Cellulose CO2 ( CO )
Pyrolysis or
Over heating
High Temperature
Oil C2H4 , H2 ( CH4 , C2H6 )
Cellulose CO ( CO2 )
Arching Oil
H2, C2H2 (CH4, C2H6, C2H4)

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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 TC < 300 C NS > 1 but NS < 1
T2
Thermal fault 300C < TC <
700C
< 0.1 > 1 1 - 4
T3 Thermal fault T > 700C < 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 (C2H2) 35 36 – 45 45
Ethylene (C2H4) 50 51 - 100 100
Ethane (C2H6) 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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SludgeContaminant
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)
6
Dissipation Factor
(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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DISSOLVED
GAS ANALYSIS
AVERAGE
LIMIT (IEC 60599)
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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ContaminantOverheating
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)
6
Dissipation Factor
(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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DISSOLVED
GAS ANALYSIS
AVERAGE
LIMIT (IEC 60599)
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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