emerging trends in diagnosis and condition assessment of power

Abstract—Health Index of transformer is a vital tool for relative

ranking of transformer from view point of its operation condition

criticality. It includes parameters that directly or indirectly affect the

operation and performance integrity of transformer. The present paper

envisages codes and criteria given under standards like IEC, IEEE,

CIGRE that are helpful for condition assessment and asset

management of power transformer . An exhaustive treatment of

affecting parameter has been covered entrusting vital information

related with criticality of Power Transformer outlay. It describes a

modern technique involving key parameters that can give clear cut

idea for classifying all transformer condition based on their HI under

the same umbrella.

Keywords—Dissolve gas analysis (DGA), Frequency domain

spectroscopy (FDS), Load Tap changer (LTC), Dissolved gas

analysis factor(DGAF),oil quality index factor(OQIF), Oil Quality

factor(OQF),Furan factor(FF) ,Load Tap changer Factor( LTCF),

Load index factor(LIF),Maintenance strategies and age factor

(MSAF).

I. INTRODUCTION

OWER transformer being most important equipment of a

power system utility whose cost accounts for around 60%

of the total investment.

The forced outage of transformer causes huge disturbances in

the electricity supply chain system and incur financial loss to

the company .Therefore its periodical or continuous condition

monitoring and proper diagnostics become crucial throughout

its life. From the time of manufacturing and transportation the

power transformer undergoes various faults and abnormalities

that may be incipient or external. Incipient fault are due to the

abnormalities within the transformer tank. That may be in its

insulation system, winding arrangement or associated parts

inside the transformer tank. These components actually

undergo various electrical and thermal stress deterioration due

to faults and abnormalities. The fault may be due to errors in

designing and malpractices in manufacturing technology that

may lead to abnormal operational parameters and deviation

Priyesh Kumar Pandey is with the National Institute of Technology,

Hamirpur, INDIA(+919805249405; e-mail:[email protected])

Harmendra singh is with the National Institute of Technology,

Hamirpur(H.P), INDIA (+9198882501243; e-mail:[email protected] )

M Rao is a faculty in EED with AITAM (.India)

R K Jarial is with the National Institute of Technology, Hamirpur(H.P),

INDIA (+919418847240; e-mail:[email protected] ).

from expected parameters. That ultimately led to failure of

transformer well below the expected life span.

Health Index (HI) is handy tool to represent the severity

and to quantify the various parameters that directly or

indirectly affect the aging and operational features of the

transformer. Also quality and priority based investment led

maintenance program can effectively optimise the asset

management 0needs [1, 2]. Several studies has been carried

out to develop a tool for asset management and monitoring of

substation and to formulate Health Index (HI) of transformers.

Introduction of smart diagnostics techniques such as SFRA,

DFR, PD Test, just to name a few, had eventually given idea

about the HI of the individual transformer on their individual

base but cannot give idea about relative HI of all transformer

within the utility on same platform simultaneously or sure shot

prescribed procedure that can cover all power transformer and

all parameters helpful to find HI because there is no

recommended standard. However HI calculation

recommended from [3] to [9] are based on all available data of

the transformer at a time.

II. PARAMETERS AND RECOMMENDED TESTS

According to the CIGRE WG 12 report, the main

subsystem of transformer that can directly or indirectly affect

the life of transformer and are involved in deterioration due to

the operational conditions are as follows [4]

A. Dielectric properties

Dielectric properties of insulation system. It consists of

major as well as minor insulation system. i.e. winding to

winding, winding to core, core to tank, interturn insulation,

insulation of bushings etc.

B. Magnetic properties

Magnetic properties of the magnetic system inside the

transformer. It consists of deterioration of core material or

clamping structure.

C. Tap changer

Tap changer healthiness .It may be referred to Load tap

changer (LTC).

D. Mechanical Integrity

Mechanical integrity of various parts of the transformer

such as bushing, tank, cooling system etc. In order to diagnose

Emerging Trends in Diagnosis and Condition

Assessment of Power Transformers Based on

Health Index

Priyesh Kumar Pandey, Harmendra Singh, M Rao, and R K Jarial

P

2nd International Conference on Emerging Trends in Engineering and Technology (ICETET'2014), May 30-31, 2014 London (UK)

http://dx.doi.org/10.15242/IIE.E0514591 108

faults within Power Transformer some important tests are

required to be conducted as per IEC/ASTM. TABLE I below

enumerate details of such test

TABLE I

CONDITION ASSESSMENT TEST

Online tests

Tests Detections Instruments

Dissolved

Gas

analysis

(DGA)

Measure gas concentration,

detects gas

intensity(ppm/time period),

sparking, Hotspot, Bad

electrical contact, Electric

discharge(High and low

energy) , Overheating,

cellulosic deterioration,

Internal flashover,

healthiness of insulation

system

Portable Dissolved Gas

Analyser, Kelmen,

Distributor India pvt ltd,

Bangalore.1

Partial

discharge

Partial discharge Partial discharge detection

using acoustic emission1.

Oil physical &

chemical

tests

Moisture in oil 1. DominoMoisture

in oil analyser(online)1

2. Karl fisher

Coulometric Titrator

(offline)1

Metal counts UV-VIS

spectrophotometer1

Furans cellulosic

deterioration

High performance liquid

chromatography (HPLC)1

sludge and sediment

formation

sludge and sediment

measuring system1

Acidity of oil Automatic acidity Titrator-

10200000 1

Oxidation inhibitor in oil Fourier Transform Infrared

Spectrometer1

Interfacial Tension Interfacial Tension

Analyser1

End of life of insulation

integrity(paper & oil +paper),

healthiness of insulation

system

Require laboratory

analysis for degree of

polymerization (DP)

measurement.

Oil

Electrical

tests

AC dielectric loss of oil,

Contamination, Relative

permittivity(dielectric

constant)

Automatic Capacitance &

tan delta test set(ELTEL)1

Breakdown voltage Microprocessor based oil

breakdown test1

Oil

Thermal

test

Flash point Automatic Flash point

Apparatus Model-FLPH,

Grabner Instrument1

Pour Point Pour point tester1

Paper

insulation

thermal test

Combined TGA-DTA-DSC Measures the thermal

changes in oil, oxidation

induction and

identification of paper

insulation degradation1

Physical

Inspection

(external)

Oil leaks, broken parts and

damages, cracks and external

arcing and overheating, loose

bolts and connections, pump

and radiators problems, Dust

accumulation of bushing and

its outer insulation system,

cooling problems, gauge

Done by expert staff with

binoculars for bushing

and lightening arrester

workings

Infrared

scan(IR

Imaging)

Hot spot, localised heating,

loose connections and joints,

Internal overheating(By

action of thermal

transmission), differential

over heating, cooling

troubles, overloading of

phases, circulating current,

bushing and Lightening

arrester thermal problems

Infrared thermal

imaging Camera1

Ultra sonic

and sonic

faults

detection

Internal partial discharge,

arcing , sparking, pump and

bearing impeller problems,

internal flash

UHF sensors and

Acoustic sensors

*Vibration

analysis

Internal core and winding

vibrations shield problems,

loose bolting.

Portable Dingle channel

Data collector cum

vibration analyser1

Sound

Level

Core energies problems and

external noise to compare

baseline for vibration tests

Sound level meter(e.g.

Quest 2400 sound meter)

Pollution,

humidity

level

Atmospheric conditions that

affect the flashover, treeing

and tracking

Corona Compare bushing and

Lightening arrester and all

high voltage connections

with same units

Corona scope, model cs-01-A

Offline tests

Doble

Power

factor and

insulation

resistance

between

ph-ph, ph –

ground

Loss of winding and bushing

insulation integrity, moisture

and contamination in

insulation of winding and

bushing.

Doble Test Equipment1

*Solid

insulation

electrical

tests

Dielectric frequency response

of paper insulation for

moisture determination

Automatic Insulation

Diagnostics Analyser

Model-DIRANA1

Excitation

current

Shorter turns of the winding

and phase connections

problems


*Turns ratio Shorted winding turns and

voltage ratio errors Doble Test Equipment

1

*Leakage

reactance/s

hort circuit

impedance

test

Change in percentage

impedance with the specified

name plate values


*Sweep

frequency

response

analysis(SF

RA)

Core and Winding

dislocation, Structural

integrity, transportation

damages

SFRA model

No.M5200,DOBLE1

Internal

Inspection

Oil sludging, displacement of

winding, loose connection ,

internal sparking and arcing

Boroscope

*Degree of

polymerizat

ion

Cellulosic insulation

deterioration and Life

expectancy

Require laboratory

analysis

1this equipment is available from National institute of

technology, Hamirpur (H.P) (INDIA) under TIFAC-CORE

centre on Power Transformer Diagnosis *Following test does not show health of the transformer as

its abnormal value cannot be compromised it needs immediate

action for preventing catastrophic failure or transformer may



be declared faulty.

This paper along with testing techniques [5] gives

consolidated parameters that can affect the performance

indices and life of transformer

a) Vibration of core

b) Environmental condition (Humidity, pollution level, rain per

year, altitude of the site, number of surges and their

intensity)

III. METHODOLOGY

The most common methods currently used for condition

monitoring and diagnostics of Power Transformer are as below

[5].i.e.

A. Dissolved gas analysis (DGAF)

B. Oil quality factor(OQF)

C. Furfural Factor(FF)

D. Load Tap changer factor (LTCF).

E. Load history and Maintenance data(LIF).

A. Dissolved gas analysis (DGA)

DGA technique is well known tool for preventive

maintenance and its interpreted results may indicate active

incipient faults or abnormalities within the transformer tank.

However DGA should be individually taken for bushings and

all other oil filled terminals for complete diagnosis of

transformer. Routine test, diagnostics methods finds the gas

generations and measures the gas ratios. Mechanism for the

gas generation in the transformer may be arcing, partial

discharge, low energy discharge, overheating of insulation due

to severe overloading, failure of forced cooling systems or any

of the above. Practically DGA interpretation by itself cannot

provide sufficient information for incipient fault and

abnormalities to evaluate the integrity of the transformer and

its various subsystem because the governing standard fail to

evaluate condition for some abnormal ratios.

Several classis method and methods has been evolved for

DGA interpretation over the past 30 years such as Rogers,

Dorenburg, Duval triangle and modified Dorenburg

.[6],[7],[8],[9].

A1.1 Rogers’s ratio

The Rogers ratio is a simple scheme based on ranges of

ratios is used for diagnoses of faults. It uses four gas ratios

that are CH4/H2, C2H6/CH4, C2H4/C2H6 and C2H2/C2H4

[4]. The four conditions of the oil insulated transformer that

are detectable are normal ageing, partial discharge with or

without tracking, electrical and thermal faults of various

degree of severity. This method is also based on thermal

degradation principles and is also included in ANSI/IEEE[7]

Standard C57.104-1991. The validity of this method is based

on the correlation of results of a much larger number of failure

investigations with the gas analysis of each case. There are

diagnostic codes for the various faults and in this method there

are values of ratios that do not fit into the diagnostic codes.

Also for dissolved gases below the normal concentration

value, no consideration is given and due to this the exact

implementation of the method may lead to many

misinterpreted cases [10].

A1.2 IEC Method

Fault diagnosis scheme recommended by International

Electro technical Commission (IEC) originated from Rogers’

method except that the ratio C2H6/CH4 was dropped since it

only indicated a limited temperature range of decomposition.

Normal ageing, partial discharge of low and high energy

density, thermal faults and electrical faults of various degrees

of severity are the four conditions that are detectable.

However, no attempt is made to identify both thermal and

electrical faults into more precise subtypes. The first edition of

IEC method (IEC 60599-1978) is based on simple coding

scheme while the second edition (IEC 60599 – 1999) utilizes

the revised ratio ranges directly. Assessment of dissolved

gases for ‘normality’ limits is required before being

interpreted using ratios. Comparison limits in ppm are shown

in Tables 2 with different recommendations. To quantify fault

levels, an idea about the scoring and weighting factor for

individual gasses is required. Scoring is numerically

representing the range amount of gas level in ppm for

calculating DGAF.

TABLE II

COMPARISON LIMITS IN PPM

Gas Dorenburg

(ppm) IEC(ppm)

IEEE

(ppm)

Bureau of reclamation

(ppm)

H2 200 100 100 500

CH4 50 75 120 125

C2H6 35 75 65 75

C2H4 80 75 50 175

C2H2 5 3 35 7

CO 500 700 350 750

CO2 6000 7000 2500 10000

Weighting factor represent the importance of the gas level

for diagnostics based on particular diagnostics methods. It

may happen that the weighting factor of particular gas differs

from test to test. The detail are presented in Table 3.

TABLE III

SCORING AND WEIGHTING FACTOR FOR DGA GAS LEVEL [PPM][11].

Score(Si) Weight

(Wi) Gas 1 2 3 4 5 6

H2 ≤100 101-

200

201-

300

301-

700

701-

1800

>1800 2

CH4 ≤120 121-

175

176 –

350

351-

600

601-

1000

>1001 3

C2H6 ≤65 65-

80

80-

100

100-

120

120-

150

>150 3

C2H4 ≤50 50-

80

80-

100

100-

150

150-

200

>200 3

C2H2 ≤5 6-15 16-

35

35-

50

50-

80

>80 5

C O ≤350 350-

700

700-

900

900-

1100

1100-

1400

>1400 1

CO2 ≤2500 ≤3000 ≤4000 ≤ 5000 ≤7000 >7000 1

TDCG 690 691-1250 1251-

1785

1785-

2720

2721-

4630

>4700 3



Interpretation of result is one of major challenges in diagnosis

process which is given in Table-4

TABLE IV

INTERPRETATION OF RESULT IN GAS DISSOLVED IN OIL [14]

Gases Interpretation

Oxygen(O2) Transformer seal fault Carbon monoxide(C O) Cellulose degradation Carbon Dioxide (CO2) Cellulose degradation Hydrogen(H2) Electric Discharge(partial discharge,

corona) with overheating Acetylene(C2H2 ) Electric Fault (Arcing, sparking ,

Internal flash) Ethylene(C2H4) Thermal Fault (High Hot

Spots formation and local overheating ) Ethane(C2H6) Secondary indicator of Thermal Fault Methane(CH4) Secondary indicator of Arc

or serious overheating TDCG CH4+C2H6+C2H4+C2H4+C2H2

+H2+CO+O2

Based on the scoring and weight factor for gas levels

given in table 3, A ranking method can be developed as

equation 1 as Dissolved Gas Analysis Factor (DGAF)[11]

(1)

Where “Si” is the scoring for each gas based in table 2 and

Wi is weighting factor allocated for each individual gas level.

With different values of DGAF ≥0.1, different conditions of

transformer can be concluded as given in table 5 below.

TABLE V

CONDITION BASED ON DGAF

Rating

Code Condition Description

4 Very Good DGAF<1.2

3 Good 1.2≤DGAF<1.5

2 Fair and acceptable 1.5≤DGAF<2

1 Fair but Caution 2≤DGAF<3

0.01 Need attention DGAF≥3

However it is recommended that proper period of oil

sampling and DGA should be done, if the result found is not

satisfactory and the condition is transformer is no below Fair

and acceptable values

B. Oil quality

Oil quality is a good indicator of condition of transformer, its

electrical, chemical properties clearly indicate the

deterioration of the internal parts of the transformer subsystem

but it has disadvantage that if the regular reclamation is being

carried out then actual condition of insulation inside the

transformer winding cannot be predicted. However evaluation

based on oil quality can be done by considering table 6

testing.

Oil quality is a good indicator of condition of transformer,

its electrical, chemical properties clearly indicate the

deterioration of the internal parts of the transformer subsystem

but it has disadvantage that if the regular reclamation is being

carried out then actual condition of insulation inside the

transformer winding cannot be predicted. However evaluation

based on oil quality can be done by considering table 6

testing.

TABLE VI

OIL QUALITY SCORE AND WEIGHT

Sr. Test IEC ASTM IS Score

(Si) Wi

1. Color and

appearance

ISO

2049

D-1524 IS-335 1,2,3,4 1

2. Dielectric

Breakdown

voltage

IEC-

60156

D-877 IS-6792 1,2,3,4 1

3. Water

content or

moisture

IEC-

60814

D-

1533B

IS-

13567

1,2,3,4 4

4. Acidity(NN

)

IEC-

62021

D-974 IS-1448

(P-2)

1,2,3,4 2

5. Dielectric

dissipation

factor(D)

IEC-

60247

D-924 IS-6262 1,2,3,4 3

6. Resistivity IEC-

60247

D-924 IS-6103 1,2,3,4 1

7. Sediments

and sludge

IEC-

61125

D-1524 IS-1866 1,2,3,4 1

8. Interfacial

Tension

ISO-

6295

D-971 IS-6104 - 1

9. Flash point ISO-

2719

D-92 IS-1448 1,2,3,4 1

10. Pour point ISO-

3016

D-97 IS-1448 1,2,3,4 1

11. Density IEC-

60814

D-1298 IS-1448 1,2,3,4 1

12. Kinematic

Viscosity

ISO-

3104

D-445 IS-1448

(P-25)

1,2,3,4 1

B.1 Transformer oil classification based on Neutralization

number (NN) and Interfacial Tension (IFT) and color [15]

In order to classify level of degradation of insulating liquid in

power transformer oil quality index number is ascertained as

Oil Quality Index Number (OQIN) =

TABLE VII

PROVIDE DETAIL OF MONITORING “OQIN”

Parameter

s

Range of values Quality of oil Score(Si)

IFT 30.0-45.0 Healthy and efficient, oil

in very good condition

4

NN 0.00-0.04

COLOUR PALE YELLOW

OQIN 300-1500

IFT 27.1-29.9 Beginning of sludge

Formation, Oil condition

normal

3

NN 0.05-0.10

COLOUR YELLOW

OQIN 270-600

IFT 24.0-27.0 Acid formation and

sludge accumulation on

winding and insulation

voids, oil need

Reclamation

2

NN 0.11-0.15

COLOUR BRIGHT

YELLOW

IFT 14.0-23.9 Continuous acid

formation and

deterioration of

transformer internals and

insulation system

1 NN 0.16-0.65

COLOUR AMBER,

BROWN,

OQIN 22-159

IFT <13.9 Sludge has been

deposited in and on

transformer parts at all

possible reach and

equipment may fail at any

time

0.01 NN >0.66

COLOUR DARK BROWN,

BLACK

OQIN <21



The Dielectric strength test of oil is not extremely important

as the moisture in combination with oxygen and heat will

deteriorate cellulose insulation much before the dielectric

strength of oil indicates any symptom of abnormality. It also

lacks about information of sludge and acid formation.

Resistivity (specific resistance ρ) It is ratio of the DC potential

gradient in volt per centimeter paralleling the current flow

within the specimen to the current density in ampere per

square centimeter at a given instant of time and under

prescribed condition, measured in Ω-cm. It represents the

electrical property of oil in the test condition. Higher the value

of resistivity lower is the value of free oil, ion-forming

particle and no electrically active contamination. Based on the

above weighting and scoring percentage given in table 6, Oil

Quality Factor (%OQF) can be calculated as in equation (2)

(%)OQF= (2)

C. Furfural analysis

Furans are the group of organic compound that are formed

by the deterioration of cellulosic material in the transformer.

Overheating along with moisture and oxidation accelerate the

degradation of paper that results in furanic compounds.

Furfural test along with Degree of polymerization (DP) test

provide the information about the degradation of paper

insulation in the transformer oil. High level of carbon dioxide

and carbon monoxide generation indicate the need of furfural

analysis. Types of Furans that can be formed are [12].

1. 2-Furaldehyde(2-Fal)

2. 2-acetyl furan(2-ACF)

3. 2-Furfuryl alcohol(2-FOL)

4. 5-methul-2-furaldenhyde(5-MEF)

5. 5-hydroxylemethy-2-furaldehyde(5-HMF)

For scoring of the Furan analysis for transformer following

table 8 is helpful TABLE VIII

CONDITION OF TRANSFORMER BASED ON FURFURAL ANALYSIS

Normal

Paper

at 55 C

(2-FAL

counts)

hermally

upgraded

paper 65 C

(Total

Furan

counts)

Degree of

Polymerization

(DP)

Condition of

paper based on

Furan analysis

Furfural

factor

(FF)

60-300 50-200 800-6003 Normal

ageing 4

650-

2000

390-980 500-360 Accelerated

ageing 3

2375-

3275

1115-1450 340-300 Excessive

ageing,

Equipment in

danger zone

2

3850-

4525

1665-1900 280-260 High risk of

failure or high

probability of

fail

1

5300-

7333

2175-2845 240-200 End of life of

paper insulation 0.01

D. Tap changer (LTC) condition [5].

Insulation of tap changer basically depends upon the insulation

in the tap changer. i.e. oil, epoxy resin, fibreglass, pressboard etc.

Therefore individual diagnostics test can give cumulative idea

about the condition of Tap changer.DGA for oil in LTC can give

idea about the condition of insulation integrity of LTC. Scoring

and weighting of different LTC for various gasses in DGA

analysis in Table 9 TABLE IX

SCORING AND WEIGHTING FACTOR FOR LTC

Score(Si) Weight

Vaccume

LTC

Gas 1 2 3 4 Wi

CH4 <30 30-

50

50-

100

>100 3

C2H6 <20 20-

30

40-

50

≥50 3

C2H4 <50 50-

100

100-

200

≥200 4

C2H2 <3 3-4 4-5 ≥5 5

Resistive

LTC

CH4 <100 100-200 200-300 ≥300 3

C2H6 <50 50-

100

100-200 ≥200 3

C2H4 <200 200-400 400-600 ≥600 5

C2H2 <500 500-

1000

1000-

5000

≥5000 3

Reactive

LTC

CH4 <50 50-

150

150-250 ≥250 3

C2H6 <30 30-

50

50-100 ≥100 3

C2H4 <100 100-200 200-500 ≥500 5

C2H2 <10 10-

20

20-

25

≥25 3

E. Maintenance strategies, loading history and age

IEEE C.57-1995 and IEC 354 give recommendation of

conductor & oil temperature inside the transformer. However

IEC gives more conservative recommendation for conductor

temperature [16]

M0: Number of Si/SB that are lower than 0.6,i=0

M1: Number of Si/SB that are between 0.6 and 1,i=1

M2: Number of Si/SB that are between 1.0 and 1.3,i=2

M3: Number of Si/SB that are between 1.3 and 1.5,i=3

M4: Number of Si/SB that are bigger than1.5,i=4

Si : monthly peak load & SB is the rated loading of the

transformer

Then Load factor index can be given as (LFI)

LIF= (4)

Based on above equation 4 score can be given as in table 10

TABLE X

SCORING OF LIF

Score

(Li)

LIF

4 LIF≥3.5

3 2.5≤LIF≤3.5

2 1.5≤LIF≤2.5

1 0.5≤LIF≤1.5

0.01 LIF≤0.5

TABLE XI



VARIOUS CORING TABLE FOR SCORING VARIOUS FACTOR FOR THI

Factors Score(Si)

DGAF 4,3,2,1,0.01

OQF 4,3,2,1,0.01

FF 4,3,2,1,0.01

LTCF 4,3,2,1,0.01

LIF 4,3,2,1,0.01

Taking the total accountability of factors given in table 11.

Total health index can be formulated as

Total health index(THI) =

TABLE XII

CONCLUDE ABOUT THE HEALTH OF TRANSFORMER AT THE TIME OF TESTING

THI Condition of

transformer

Maintenance requirement

1 Very good Normal maintenance

0.50 good Normal maintenance

0.25 poor Carry out diagnostic test and

refurbishment

<0.25 Poor and need caution Carry out diagnostic test well earlier

than normal and need clear attention

for parameter

<0.20 Very poor, invite

failure, Need urgent

replacement

Shut down transformer and carry out

refurbishment for further use and to

avoid catastrophic failure

IV. CONCLUSION

The determination of criticality level of fault in oil filled

power transformer is a virtual issue that can be resolved by

adhering to strict condition monitoring regime. The present

paper has highlighted novel technique to decide the criticality

and remedial aspect through exhaustive tests by forming HI.

The author are of firm opinion that if HI of equipment of

substation i.e. Power Transformer is evaluated, It can prevent

catastrophic failure and moreover a strategy can be evolved by

developing proper data bank of power transformer to

safeguard the Power Transformer.

ACKNOWLEDGMENT

The Author are thankful to TIFAC-CORE for providing

Testing facilities to conduct experiment and other

infrastructure for condition assessment of Power Transformer

for Thesis and Dissertation

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[11] R.Phadungthin,E.Chaidee,J .Haema, and .Suwanasari, “Analysis of

Insulating oil to evaluate the condition of power transformer”,

ECTICON, Changmai ,Thailand,May 19-21,2010.

[12] Juthathip Haema, Rantankorn Phadungthin, “Condition Assessment of

the health Index for Power ransformer”

[13] ANSI/ IEEE Std. C57.94-1982, "IEEE Recommended Practice for

Installation, Application and Maintenance of Dry-Type Distribution and

Power Transformers."

[14] IEC publication standard 60599, “Guide for interpretation of dissolved

and free gases analysis” 1999-2007-05

[15] A GUIDE TO TRANSFORMER OIL ANALYSIS BY I.A.R. GRAY

Transformer Chemistry Services

[16] An Approach to Determine the Health Index of Power Transformers A.

Naderian, S. Cress, R. Piercy, F. Wang, J. Service Kinectrics Inc.,

Transmission and Distribution Technologies 800 Kipling Avenue

Toronto, ON, M8Z 6C4

[17] Facilities Instruction, Standards and Techniques Volume 3-31

Priyesh kumar pandey graduated in Electrical

Engineering from Atmiya institute of technology

and science Rajkot, Gujarat in the year 2009. He

worked as lecturer in Atmiya institute of

technology and science Rajkot for six months.

Then he worked in Gujarat state electricity

corporation Ltd for two years in the field of

operation and maintenance. His current research

interests include insulation condition assessment

techniques, specialising in the diagnosis of solid

insulation in transformer based of moisture

assessment. He is currently pursuing his M.Tech in Condition Monitoring

Control and Protection of Electrical Apparatus from NIT Hamirpur, India

Email: [email protected]

Harmendra Singh was born in Dehradun

Uttarakhand, India. He received B.Tech. degree

in Electrical and Electronics Engineering from

Graphic Era Institute of Technology, India, He

is currently pursuing the M.Tech. degree in

Condition Monitoring Control and Protection of

Electrical Apparatus from National Institute of

Technology, Hamirpur

Dr. R K Jarial received PhD from University of Rajashtan through MNIT,

Jaipur, India in 2007 and Masters Degree from National Institute of

technology Kurukshetra, Haryana, India in 1993 respectively. He is currently

working as Assosiate Professor in Electrical Engineering Department of NIT

Hamirpur, HP, India for the last twenty years. He has obtained One Patent

and has been instrumental in the establishment of TIFAC-CORE in Power

Transformer Diagnostics at NIT Hamirpur. His current areas of interests are

Power electronic drives and High voltage engineering.











emerging trends in diagnosis and condition assessment of power

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