Transformer Fault Diagnosis Based on DGA using Classical Methods

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Transformer Fault Diagnosis Based on DGA using Classical Methods

Deepak 1,

1Student EEE Department,

RVS College of Engineering and Technology, Jamshedpur, India

Munisha Bage2

2 Student EEE Department,

RVS College of Engineering and Technology, Jamshedpur, India

Pushpanjali Singh Bisht 3

3Assistant Professor EEE Department, RVS College of Engineering and Technology,

Jamshedpur, India

Parasnath4

4Assistant Professor& HOD EEE Department, RVS College of Engineering and Technology, Jamshedpur, India

Arrik Khanna5

5 3Assistant Professor EEE Department, Chitkara University Punjab

Abstract- During the last few years there has been trend of continuous increase in transformer failures. It is therefore necessary to diagnose the incipient fault for safety and reliability of electrical network. Various faults could occur in transformer such as overheating, partial discharge and arching which can generate various fault gases so in order to diagnose the fault DGA (Dissolved gas Analysis) is done. In this paper the proposed methods are used which is based on standards and guidelines of International Electro technical Commission (IEC), Central Electric Generating board (CEGB), and the American Society for testing and Material (ASTM). Fault diagnoses methods by the DGA technique are implemented to improve the interpretation accuracy of transformer.

Keywords: Dissolved gas Analysis (DGA), Central Electric Generating board (CEGB), The American Society for testing and Material (ASTM), Institute of Electrical and Electronics Engineering (IEEE), International Electro technical Commission (IEC), British Standard (B.S.), Decomposition (Decomp).

  1. INTRODUCTION

    Transformers are the essential part of the electrical power system because it has the ability to alter voltage and current levels, which enables the power transformer to transmit and distribute electric power and utilize the power at economical and suitable levels. In electrical power system, voltage of electricity generated at the power plant will be increased to a higher level with step-up transformers. A higher voltage will reduce the energy lost during the transmission process of the electricity. After electricity has been transmitted to various end points of the power grid, voltage of the electricity will be reduced to a usable level with step-down transformer for industrial customers and residential customers. Since power transformer is vital equipment in any electrical power system, so any fault in the power transformer may lead to the interruption of the power supply and accordingly the

    financial losses will also increase. So it is of paramount importance to detect the incipient fault of transformer as early as possible. The following characteristics of oil were laid down in B.S.148:1959 the values stated being obtained by the testing method specified in the, appendices of the standard:-

    Table I: Physical Properties of Transformer Oil

    Characteristic

    Limit

    Sludge Value(max)

    1.20%

    Acidity after oxidation(max)

    2.5 mg KOH/gm

    Flash Point (closed) (min)

    295° F (146.1°C)

    Viscosity at 70°F(21.1°C)(max)

    37 cS

    Pour Point (max)

    (-25.06°F) (-31.7°C)

    Electric Strength, 1 minute (min)

    40 kV (r.m.s)

    Acidity(neutralization value) Total (max) Inorganic

    0.05mg. KOH/gm Nil

    Saponification Value (max)

    1.00 mg. KOH/gm

    Copper discoloration

    Negative

    Crackle

    Shall pass test

    Specific gravity

    No Limit

    Faults can be differentiated for their energy, localization and occurrence period. Along with a fault, there are increased oil temperatures and generation of certain oxidation products such as acids and soluble gases. These gases, hydrogen ( H2), methane ( CH4 ), ethane ( C2H6 ), ethylene ( C2H4 ), acetylene ( C2H2 ), propane ( C3H8 ), propane ( C3H6 ), together with carbon monoxide ( CO ) and carbon dioxide ( CO2 ) are considered as fault indicators and

    can be generated in certain. The operating principle of transformer is based on the slight albeit harmless deterioration of the insulation that accompanies incipient faults, in the form of arcs or sparks resulting from dielectric breakdown of weak or overstressed parts of the insulation, or hot spots due to abnormally high current densities or due to high temperature in conductors. Whatever the cause, these stresses will result in the chemical breakdown of oil or cellulose molecules constituting the dielectric insulation

  2. DISSOLVED GAS ANALYSIS

    Thermal and electrical distributions in the operating transformer are two most important causes of dissolved gases in oil. The gases produced from thermal decomposition of oil and solid insulation are because of losses in conductors due to loading. Also decomposition occurs in oil and solid insulation is due to occurrence of arc. In case of electrical disturbances the gases are formed principally by ionic bombardment. The gases are generated mainly because of cellulose and oil insulation deterioration. In the normal operation of the transformer, gases such as Hydrogen (H2), Methane (CH4), Ethylene (C2H4), Acetylene (C2H2), and Ethane (C2H6) and so on are released. In the existing methods, parts per million (PPM) values are determined for each gas in the oil along with a total value of combustible gasses. When there is an abnormal situation such as a fault occurrence, some specific gases are produced in greater quantity than in the normal operation. Thus, the amount of these gases in the transformer oil increases. The increase in the amount of gases results in saturation of the transformer oil and no further gas can be dissolved in oil. Therefore, when the oil is saturated, the gas is released from the oil. The amount of the dissolved gas is related to the temperature of the oil and the type of gas. The produced gas can be classified into three groups: polarization, corona, and arcing. These groups coming from the severity of the released energy during the fault are different. The largest and lowest amounts of the released energy are associated with the arcing and corona.

    1. Polarization: In the transformer oil, the released gases at low temperature are CH4 and C2H6, and at high temperature are C2H6, CH4, C2H4, and H2. In cellulose, the generated gases at low and high temperatures are CO and CO2.

    2. Corona: In corona, the produced gas in oil is H2 and the released gases in cellulose are H2, CO, and CO2.

      Sl. No.

      Code

      Kind of fault

      Grouping of fault

      X

      Y

      Z

      1

      0

      0

      0

      No fault

      F1

      2

      0

      1

      0

      Partial discharge with low intensity discharge

      F2

      3

      1

      1

      0

      Partial discharge with high intensity discharge

      F3

      4

      1 or

      2

      0

      1 or

      2

      Partial discharge with low intensity discharge

      F2

      5

      1

      0

      2

      Partial discharge with high intensity discharge

      F3

      6

      0

      0

      1

      Thermal fault with temperature less than 150°C

      F4

      7

      0

      2

      0

      Thermal fault with temperature between 150° C to 300° C

      F5

      8

      0

      2

      1

      Thermal fault with temperature between 300 °C to 700° C

      F6

      9

      0

      2

      2

      Thermal fault with temperature greater than 700°C

      F7

      Sl. No.

      Code

      Kind of fault

      Grouping of fault

      X

      Y

      Z

      1

      0

      0

      0

      No fault

      F1

      2

      0

      1

      0

      Partial discharge with low intensity discharge

      F2

      3

      1

      1

      0

      Partial discharge with high intensity discharge

      F3

      4

      1 or

      2

      0

      1 or

      2

      Partial discharge with low intensity discharge

      F2

      5

      1

      0

      2

      Partial discharge with high intensity discharge

      F3

      6

      0

      0

      1

      Thermal fault with temperature less than 150°C

      F4

      7

      0

      2

      0

      Thermal fault with temperature between 150° C to 300° C

      F5

      8

      0

      2

      1

      Thermal fault with temperature between 300 °C to 700° C

      F6

      9

      0

      2

      2

      Thermal fault with temperature greater than 700°C

      F7

    3. Arcing: In this case, the released gases are C H , CH ,

      Table II: IEC code determination Criteria

      Gas ratio

      Value

      Code

      X= C2H2/C2H4

      X<0.1

      0

      0.1<X<3

      1

      X>3

      2

      Y= CH4/H2

      Y<0.1

      1

      0.1<Y<1

      0

      Y>1

      2

      Z=C2H4/C2H6

      Z<1

      0

      1<Z<3

      1

      Z>3

      2

      Gas ratio

      Value

      Code

      X= C2H2/C2H4

      X<0.1

      0

      0.1<X<3

      1

      X>3

      2

      Y= CH4/H2

      Y<0.1

      1

      0.1<Y<1

      0

      Y>1

      2

      Z=C2H4/C2H6

      Z<1

      0

      1<Z<3

      1

      Z>3

      2

      Table III: Fault Diagnosis IEC codes

      C2H4, and H2.

      2 6 4

      In this method at first a sample of transformer oil is taken then the dissolved gases is extracted, separated and measured by means of chromatography. In order to interpret result of experiment data is produced is produced in suitable form to diagnose the fault. The different standard are used which are explained in following sections.

      1. Rogers ratio method I (IEC Standard)

        According to the IEC standards, the extended Rogers method is used to produce a three digit code. The code is determined based on the three gas ratios of C2H2/C2H4, CH4/H2, and C2H4/C2H6 as given in Table II.

      2. Rogers ratio method II. (CEGB Standard)

        In this standard, a four digit code is created using the Rogers method and four gas ratios of CH4/H2, C2H6/CH4, C2H4/C2H6, and C2H2/C2H4. From the obtained codes the faults are diagnosed.

        Table IV: CEGB code determination Criteria

        Gas ratio

        Value

        Code

        W=CH4/H2

        W<=0.1

        5

        0.1<W<1

        0

        1<=W<3

        1

        W>=3

        2

        X=C2H6/CH4

        X<1

        0

        X>=1

        1

        Y=C2H4/C2H6

        Y<1

        0

        1<=Y<3

        1

        Y>=3

        2

        Z=C2H2/C2H4

        Z<0.5

        0

        0.5<=Z<3

        1

        Z>=3

        2

        Table V: Fault Diagnosis using CEGB codes

      3. Rogers ratio method III (ASTM Standard)

    In this standard a four digit code is generated based on the codes given in table using the Rogers method and the four gas ratios of C2H4/C2H6, C2H6/CH4, C2H2/C2H4, and CH4/H2 is considered.

    Table VI: ASTM code determination criteria

    Gas ratio

    Value

    Code

    0<W<0.1

    1

    J=CH4/H2

    0.1<W<1

    1<=W<3

    2

    3

    W>3

    4

    K=C2H6/CH4

    X<1 X>1

    0

    1

    Y<1

    0

    L=C2H4/C2H6

    3<Y<1

    1

    Y>3

    2

    Z<0.5

    0

    M=C2H2/C2H4

    3<Z<0.5

    1

    Z>=3

    2

    S.NO

    Codes

    W X Y Z

    Kind of fault

    Grouping of fault

    1

    0

    0

    0

    0

    No fault

    F1

    2

    5

    0

    0

    0

    Partial discharge

    F2

    3

    1 or

    2

    0

    0

    0

    Increase in temperature less than equal to 150° C

    F3

    4

    1 or

    2

    1

    0

    0

    Increase in temperature 150 °C to

    200 °C

    F4

    5

    0

    1

    0

    0

    Increase in temperature 200°C-

    300°C

    F5

    6

    0

    0

    1

    0

    Increase in overall temperature in conductive parts

    F6

    7

    1

    0

    1

    0

    Circulating currents in winding

    F7

    8

    1

    0

    2

    0

    Circulating current between core and tank

    F8

    9

    0

    0

    0

    1

    Spark with low energy discharge

    F9

    10

    0

    0

    1 or

    2

    1 or 2

    Spark with high energy discharge

    F10

    11

    0

    0

    2

    2

    Continuous spark

    F11

    12

    5

    0

    0

    1 or 2

    Partial discharge with tracking

    F12

    S.NO

    Codes

    W X Y Z

    Kind of fault

    Grouping of fault

    1

    0

    0

    0

    0

    No fault

    F1

    2

    5

    0

    0

    0

    Partial discharge

    F2

    3

    1 or

    2

    0

    0

    0

    Increase in temperature less than equal to 150° C

    F3

    4

    1 or

    2

    1

    0

    0

    Increase in temperature 150 °C to

    200 °C

    F4

    5

    0

    1

    0

    0

    Increase in temperature 200°C-

    300°C

    F5

    6

    0

    0

    1

    0

    Increase in overall temperature in conductive parts

    F6

    7

    1

    0

    1

    0

    Circulating currents in winding

    F7

    8

    1

    0

    2

    0

    Circulating current between core and tank

    F8

    9

    0

    0

    0

    1

    Spark with low energy discharge

    F9

    10

    0

    0

    1 or

    2

    1 or 2

    Spark with high energy discharge

    F10

    11

    0

    0

    2

    2

    Continuous spark

    F11

    12

    5

    0

    0

    1 or 2

    Partial discharge with tracking

    F12

    Table VII: Fault Diagnosis using ASTM codes

    Sl.

    No.

    Codes

    Kind of Fault

    Grouping of fault

    W

    X

    Y

    Z

    1

    2

    0

    0

    0

    Normal

    F1

    2

    1

    0

    0

    0

    Partial discharge

    F2

    3

    3

    0

    0

    0

    Increase in temperature less than equal than 150 C

    F3

    4

    4

    0

    0

    0

    Increase in temperature less than equal than 150 C

    F3

    5

    3

    1

    0

    0

    Increase in temperature 150C-200C

    F4

    6

    4

    1

    0

    0

    Increase in temperature 150C-200C

    F4

    7

    4

    0

    1

    0

    Increase in temperature 200 C to 300 C

    F5

    8

    2

    0

    1

    0

    Increase in temperature of conductor

    F6

    9

    3

    0

    1

    0

    Circulating current in winding

    F7

    10

    3

    0

    2

    0

    Circulating current between core and tank

    F8

    11

    2

    0

    0

    1

    Spark with very low energy density

    F9

    12

    2

    0

    1

    1

    Spark with high energy density

    F10

    13

    2

    0

    1

    2

    Spark with high energy density

    F10

    14

    2

    0

    2

    1

    Spark with high energy density

    F10

    15

    2

    0

    2

    2

    Continuous spark

    F11

    16

    1

    0

    0

    1

    Partial discharge with tracking

    F12

  3. DUVAL TRIANGLE METHOD

    This method is more graphical method than ratio method. Duval triangle method uses concentration of the three key gases for the diagnosis of fault. These gases are CH4 (Methane), C2H4 (Ethylene), C2H2 (Acetylene).

    The ratio of the gases is calculated using the expressions as below:

    CH4% = (100 X) / (X+Y+Z) C2H4% = (100 Y) / (X+Y+Z) C2H2% = (100Z) / (X+Y+Z)

    Where X = CH4 in p.p.m Y = C2H4 in p.p.m Z = C2H2 in p.p.m

    These values are then plotted on the triangle. The point of interception falls into a zone in the triangle which depicts the fault in the transformer.

    Fig I:

    Where,

    PD depicts Partial Discharge.

    T1 depict thermal fault below 300°C.

    T2 depict thermal fault between 300°C to 700°C T3 depict thermal fault with overhauling.

    D1 depicts low energy discharge (Spark)

    D2 depicts high energy discharge (Electric Arc)

    DT depicts a mix between thermal and electric faults.

  4. DOERNENBURG RATIO METHOD

    This method utilizes the gas concentration from ratio of CH4/H2, C2H2/CH4, C2H4/C2H6, C2H2/C2H4.

    Table VIII:Fault diagnosis using Doernenburg Ratio

    M

    N

    O

    P

    CH4/H2

    C2H2/C2H4

    C2H6/C2H2

    C2H2/CH4

    Suggested Fault Diagnosis

    >0.1

    <0.75

    >0.4

    <0.3

    Thermal Decomposition

    <0.1

    <0.001

    >0.75

    <0.4

    >0.3

    Corona (Low Intensity PD)

    <0.1

    <0.75

    >0.4

    <0.3

    Arcing(High Intensity PD)

    PROBLEM 1

    DGA result of TATA STEEL, Jamshedpur (Tata Nagar). Equipment: 15/18.75 MVA

    Make BHEL

    Rated Voltage: 420/220/33 KV

    Rated current: 434/526.6/837.03 Ampere

    Table VIII: DGA result of Transformer

    FAULTY GASES

    Sl.

    No.

    H2

    CH4

    C2H6

    C2H4

    C2H2

    CO

    CO2

    1

    178

    506

    176

    583

    11.7

    151

    1844

    2

    315

    865

    510

    2062

    1

    233

    4851

    3

    383

    1040

    534

    2315

    2

    233

    4851

    4

    380

    363

    308

    1700

    61.5

    48

    1683

    5

    279

    192

    255

    746

    0

    136

    2831

    6

    695

    1340

    629

    2720

    2.5

    335

    5655

    7

    253

    174

    233

    718

    0

    98

    2477

    8

    5239

    40972

    6101

    7784

    233.9

    588

    5222

    9

    173

    161

    79

    417

    9.5

    21

    1000

    ROGER'S RATIO

    Fault Gases(IEC STANDARD)

    RATIO

    CODES

    S.

    No.

    X

    Y

    Z

    X

    Y

    Z

    Kinds of Faults

    1

    0.02

    2.84

    3.312

    0

    2

    2

    Thermal fault with temp

    >700ºC

    2

    0.0004

    2.74

    4.04

    0

    2

    2

    Thermal fault with temp

    >700°C

    3

    0.0008

    2.71

    4.33

    0

    2

    2

    Thermal fault with temp

    >700°C

    4

    0.0361

    0.95

    5.51

    0

    2

    2

    Thermal fault with temp

    >700°C

    5

    0

    0.688

    2.92

    0

    2

    1

    Thermal fault having temp b/w 300 &

    700°C

    6

    0.0009

    1.928

    4.32

    0

    2

    2

    Thermal fault with temp

    >700°C

    7

    0

    0.679

    3.081

    0

    2

    2

    Thermal fault with temp

    >700°C

    8

    0.030

    7.82

    1.275

    0

    2

    1

    Thermal fault having temp b/w 300 &700°C

    9

    0.022

    0.93

    5.27

    0

    2

    2

    Thermal fault with temp

    >700°C

    ROGER'S RATIO

    Fault Gases(ASTM STANDARD)

    Ratio

    Codes

    Fault

    S.

    No.

    W

    X

    Y

    Z

    W

    X

    Y

    Z

    Kinds of Faults

    1

    2.84

    0.347

    3.312

    0.020

    3

    0

    2

    0

    Circulating current bet. core & tank

    2

    2.74

    0.589

    4.0431

    0.00048

    3

    0

    2

    0

    Circulating current bet. core & tank

    3

    2.715

    0.513

    4.335

    0.00086

    3

    0

    2

    0

    Circulating current bet. core & tank

    4

    0.955

    0.848

    5.5194

    0.03617

    2

    0

    2

    0

    No Result

    5

    0.688

    1.328

    2.925

    0

    2

    1

    1

    0

    No Result

    6

    1.928

    0.4694

    4.324

    0.00091

    3

    0

    2

    0

    Circulating current bet. core & tank

    7

    0.687

    1.339

    3.0815

    0

    2

    1

    2

    0

    No Result

    8

    7.82

    0.1489

    1.2758

    0.030

    4

    0

    1

    0

    No Result

    9

    0.93

    0.4906

    5.278

    0.0227

    2

    0

    2

    0

    No Result

    ROGER'S RATIO

    Fault Gases(ASTM STANDARD)

    Ratio

    Codes

    Fault

    S.

    No.

    W

    X

    Y

    Z

    W

    X

    Y

    Z

    Kinds of Faults

    1

    2.84

    0.347

    3.312

    0.020

    3

    0

    2

    0

    Circulating current bet. core & tank

    2

    2.74

    0.589

    4.0431

    0.00048

    3

    0

    2

    0

    Circulating current bet. core & tank

    3

    2.715

    0.513

    4.335

    0.00086

    3

    0

    2

    0

    Circulating current bet. core & tank

    4

    0.955

    0.848

    5.5194

    0.03617

    2

    0

    2

    0

    No Result

    5

    0.688

    1.328

    2.925

    0

    2

    1

    1

    0

    No Result

    6

    1.928

    0.4694

    4.324

    0.00091

    3

    0

    2

    0

    Circulating current bet. core & tank

    7

    0.687

    1.339

    3.0815

    0

    2

    1

    2

    0

    No Result

    8

    7.82

    0.1489

    1.2758

    0.030

    4

    0

    1

    0

    No Result

    9

    0.93

    0.4906

    5.278

    0.0227

    2

    0

    2

    0

    No Result

    Table X: Diagnose of fault by ASTM method

    Table IX: Diagnose of fault by IEC method

    ROGERS RATIO

    Fault Gases(CEGB STANDARD)

    Ratio

    Codes

    Fault

    S.

    No

    W

    X

    Y

    Z

    W

    X

    Y

    Z

    Kinds of Faults

    1

    2.84

    0.347

    3.312

    0.020

    1

    0

    2

    0

    Circulating current bet. core & tank

    2

    2.74

    0.589

    4.0431

    0.00048

    1

    0

    2

    0

    Circulating current bet. core & tank

    3

    2.715

    0.513

    4.335

    0.00086

    1

    0

    2

    0

    Circulating current bet. core & tank

    4

    0.955

    0.848

    5.5194

    0.03617

    0

    0

    2

    0

    No Result

    5

    0.688

    1.328

    2.925

    0

    0

    1

    1

    0

    No Result

    6

    1.928

    0.4694

    4.324

    0.00091

    1

    0

    2

    0

    Circulating current bet. core & tank

    7

    0.687

    1.339

    3.0815

    0

    0

    1

    2

    0

    No Result

    8

    7.82

    0.1489

    1.2758

    0.030

    2

    0

    1

    0

    No Result

    9

    0.93

    0.4906

    5.278

    0.0227

    0

    0

    2

    0

    No Result

    ROGERS RATIO

    Fault Gases(CEGB STANDARD)

    Ratio

    Codes

    Fault

    S.

    No

    W

    X

    Y

    Z

    W

    X

    Y

    Z

    Kinds of Faults

    1

    2.84

    0.347

    3.312

    0.020

    1

    0

    2

    0

    Circulating current bet. core & tank

    2

    2.74

    0.589

    4.0431

    0.00048

    1

    0

    2

    0

    Circulating current bet. core & tank

    3

    2.715

    0.513

    4.335

    0.00086

    1

    0

    2

    0

    Circulating current bet. core & tank

    4

    0.955

    0.848

    5.5194

    0.03617

    0

    0

    2

    0

    No Result

    5

    0.688

    1.328

    2.925

    0

    0

    1

    1

    0

    No Result

    6

    1.928

    0.4694

    4.324

    0.00091

    1

    0

    2

    0

    Circulating current bet. core & tank

    7

    0.687

    1.339

    3.0815

    0

    0

    1

    2

    0

    No Result

    8

    7.82

    0.1489

    1.2758

    0.030

    2

    0

    1

    0

    No Result

    9

    0.93

    0.4906

    5.278

    0.0227

    0

    0

    2

    0

    No Result

    Table X1: Diagnose of fault by CEGB method Table XII: Diagnosis of fault using DUVAL Triangle method

    DUVAL TRAINGLE METHORD

    PERCENTAGE

    FAULTS

    Sl. No

    %CH4

    %C2H2

    %C2H4

    TRANSFORMER FAULT DIAGNOSIS

    1

    45.84

    52.82

    1.06

    Thermal fault with temp >700° C

    2

    29.54

    70.42

    0.03

    Thermal fault with temp >700° C

    3

    30.98

    68.96

    0.059

    Thermal fault with temp >700° C

    4

    17.08

    80.01

    2.89

    Thermal fault with temp >700° C

    5

    20.46

    79.53

    0

    Thermal fault with temp >700° C

    6

    32.98

    66.95

    0.061

    Thermal fault with temp >700° C

    7

    19.50

    80.49

    0

    Thermal fault with temp >700° C

    8

    83.63

    15.88

    0.477

    Thermal fault below 700° C

    9

    27.40

    70.97

    1.617

    Thermal fault with temp >700° C

    Table XIII: Fault Diagnose of fault by Doernenburg ratio method.

    DOERNENBURG RATIO

    RATIO

    FAULT

    Sl. No

    M

    N

    O

    P

    TRANSFORMER FAULT DIAGNOSIS

    1

    2.84

    0.020

    15.04

    0.023

    Thermal Decomp

    2

    2.74

    0.00048

    510

    0.0011

    Thermal Decomp

    3

    2.715

    0.00086

    267

    0.00192

    Thermal Decomp

    4

    0.955

    0.03617

    5

    0.169

    Thermal Decomp

    5

    0.688

    0

    N.R.

    p>0

    Thermal Decomp

    6

    1.928

    0.00091

    251.6

    0.00186

    Thermal Decomp

    7

    0.687

    0

    N.R.

    0

    Thermal Decomp

    8

    7.82

    0.030

    26.08

    0.005708

    Thermal Decomp

    9

    0.93

    0.0227

    8.31

    0.0590

    Thermal Decompo

  5. CONCLUSION

In this thesis the analysis of dissolved gas of transformer is used to diagnose the fault in the transformer using Rogerss ratio through IEC, CEGB, ASTM standards parallel with DUVAL triangle and Doernenburg method. These techniques are implemented for better decision on the power transformer state and classification of power transformer fault using dissolved gas analysis as input data. It is presented here that how one technique is superior over the other for diagnosing the fault of the transformer in the most convenient manner. This shows great promise in that a number of faults likely to cause future trouble in service have been detected, although in each case the transformer had satisfactorily passed the routine tests. The technology presently exists and is being used to detect and determine fault gases below the part per million levels. However there is still much room for improvement in the technique, especially in developing the methods of interpreting the results and correlating them with incipient faults.

REFRENCES

  1. Bhalla ,Deepika., Kumar Bansal, Raj. and Gupta, Hari Om(2008). Transformer Incipent fault diagnosis based on DGA using fuzzy logic Internal Journal 2008.

  2. IEEE Std C57.104-199, 1992, "IEEE Guide for the Interpretation of Gases Generated in Oil Immersed Transformers". IEEE Press, New York

  3. Rogers R. R., 1978, "IEEE and IEC code to interpret incipient faults in transformers using gas in oil analysis ", IEEE transaction electrical Insulation., ,Vo.13,No.5, 349-354

  4. DiGiorgio, J.B. (2005) Dissolved Gas Analysis of Mineral Oil Insulating Fluids. DGA Expert System A Leader in Quality, Value and Experience 1, 1-17

  5. Dornerburg, E. and Strittmatter, W, Monitoring oil cooling transformers by gas analysis, Brown Boveri Review, vol61, May 1974, pp. 238-247.

  6. Duval, M., 1989, "Disssolved gas analysis, It can save your transformer", IEEE Electrical Insulation Man., Vo.5, No.6, 22-27.

  7. Gradnik, K. M., Physical-Chemical Oil Tests, Monitoring and Diagnostic of Oil-filled Transformers. Proceedings of 14th International Conference on Dielectric Liquids, Austria, July 2002

  8. Haupert ,T. J., Jakob, F., and Hubacher, E. J., 1989, "Application of a new technique for the interpretation of dissolved gas analysis data" 1lth Annual Technical Conference of the International Electrical Testing Association, 43-51.

  9. Herbert G. Erdman (ed.), Electrical insulating oils, ASTM International, 1988 ISBN 0-8031-1179-7, p.108.

  10. Hooshmand R., Banejad M., 2006 "Application of Fuzzy Logic in Fault Diagnosis in Transformers using Dissolved Gas based on Different Standards", World Academy of Science, Engineering and Technology,No.17.

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