DISSOLVE GAS ANYLYSIS MEASUREMENT AND

INTERPRETATION TECHNIQUES

ARUN KUMAR UNDER THE GUIDANCE OF

1AY11EE019 N. VEERANJI REDDY

CONTENTS

INTRODUCTION

MOTTO

OBJECTIVES

WORKING

INTERPRETATION OF DGA DATA

ADVANTAGES

CONCLUSION

REFERENCE

INTRODUCTION It uses the concentrations of various gases dissolved in the transformer oil due

to decomposition of the oil and paper insulation.

Dissolved gas analysis (DGA) is used to assess the condition of power

transformer.

Due to the thermal and electrical stresses that the insulation of operating

transformers experience, paper and oil de-composition occurs, generating gases

that dissolve in the oil and reduce its dielectric strength .

Gases generated through oil de-composition include hydrogen (H2), methane

(CH4), acetylene (C2H2), ethylene (C2H4), and ethane (C2H6). On the other

hand, carbon monoxide (CO) and carbon dioxide (CO2) are generated as a result

of paper decomposition.

MOTTO

Insulating materials within transformers and electrical equipment break down to

liberate gases within the unit.

The distribution of these gases can be related to the type of electrical fault, and

the rate of gas generation can indicate the severity of the fault.

 The identity of the gases being generated by a particular unit can be very useful

information in any preventative maintenance program.

OBJECTIVES

Analyse each method for condition assessment for power transformer to DGA.

Explanation for each method and compare their accuracy.

Explore good accuracy method for condition assessment of power transformer to

DGA.

GAS CHROMATOGRAPH

HYDROGEN ON-LINE MONITOR

PHOTO-ACOSTIC SPECTROSCOPY

INTERPRETATION OF DGA DATA

KEY GAS METHOD.

ROGERS RATIO METHOD.

IEC GAS RATIO METHOD.

DOERNENBURG RATIO METHOD.

DUVAL’S METHOD.

KEY GAS METHODThe principal of key gas method depend on the quantity of fault gases release in mineral oil when

fault occur.

If thermal decomposition occur in oil produce principal gas is ethylene(C2H4) and if it is

cellulose produce carbon monoxide (CO).

Low energy electrical discharges produce hydrogen and methane ,with small quantities of ethane

and ethylene and principal gas is hydrogen (H2).

High intensity arcing produce large amounts of hydrogen and acetylene are produced ,with minor

quantities of methane and ethylene and principal gas is acetylene (C2H2).

ROGERS RATIO METHOD

It diagnosis faults by taking the gas ratios and it is uses the four gas ratios are C2H2 /C2H4 ,

CH4/H2, C2H6/CH4 and C2H4/C2H6

It indicates faults like partial discharge with and without arcing, normal ageing ,thermal faults

and electrical faults simultaneously

It includes the extra gas ratio concentration C2H4/CH4 compare with IEC gas ratio method,

because it indicates low energy thermal faults .

IEC RATIO ANALYSIS

It diagnosis the faults by taking the gas ratio’s range.

They are

C2H2 /C2H4 , CH4/H2, C2H4/C2H6

It indicates the following type of faults

Normal ageing, partial discharge, low and high energy density

High energy of thermal faults and electrical faults

It can’t be indicate combination of electrical and thermal faults

DOERNENBURG RATIO METHOD

This diagnostic method mainly based upon the thermal degradation principles of oil and cellulose

decomposition.

Ratio 1 (p) = CH4 /H2

Ratio 2 (Q) = C2H2/C2H4

Ratio 3 (R) = C2H2 /CH4

Ratio 4 (S) = C2H6/C2H2

This procedure requires significant levels of the gases to be present in order for the diagnosis to be

valid.

DUVAL METHOD It is based on the use of three fault gases

CH4, C2H4 and C2H2

by taking relative percentage of these three gases, it indicates the faults

Three types of faults are detectable

Partial discharge,

high and low energy arcing (electrical faults) ,

various temperature ranges ( temperature faults)

These fault types will be determined in 7 zones of individual faults

pd-partial discharge, d1- discharge of low energy, d2- discharge of high energy,

t1-thermal faults<3000c, t2- thermal faults 3000c-7000c, t3- thermal faults >7000c

DT- combination of electrical and thermal faults

ADVANTAGES

Advance warning of developing faults.

Status check on new and aged units.

Convenient scheduling of repairs.

Identifies degradation before it leads to failure.

Determining the improper use of units.

Monitoring of units under over load.

CONCLUSION

Three methods of measuring the concentrations of fault gases dissolved in transformer oil,

namely gas chromatography, hydrogen on-line monitoring, and photo-acoustic spectroscopy,

are discussed in this article.

The high accuracy of gas chromatography is widely acknowledged. However, gas

chromatography measurements are expensive and time consuming, and industry therefore tends

to favor hydrogen on-line monitoring and photo-acoustic spectroscopy.

Hydrogen on-line monitoring can detect incipient faults but cannot provide detailed fault

diagnosis. Photo-acoustic spectroscopy provides more accurate gas concentration data than

hydrogen on-line monitoring, but its accuracy may be affected by external gas pressure and

vibration. CONT...

CONT…

Several methods are available for the interpretation of DGA data, the

doernenburg, rogers, IEC ratio, duval triangle, and key gas methods being widely

used by utilities.

However, in some cases a certain amount of engineering judgment may be

required to obtain a credible diagnosis.

REFERENCESH.-C. Sun, Y.-C. Huang, and C.-M. Huang, “A review of dissolved gas analysis in power transformers,”

energy procedia, vol. 14, pp. 1220– 1225, 2012.

Standard test method for analysis of gases dissolved in electrical insulating oil by gas chromatography, astm

d3612-02 (reapproved 2009), 2009.

T. Suwanasri, E. Chaidee, and C. Adsoongnoen, “failure statistics and power transformer condition

evaluation by dissolved gas analysis technique,” in international conference on condition monitoring and

diagnosis, 2008. CMD 2008, 2008, pp. 492–496.

A. Abu-siada and S. Islam, “A new approach to identify power trans- former criticality and asset

management decision based on dissolved gas-in-oil analysis,” IEEE trans. Dielectr. Electr. Insulation, vol.

19, pp. 1007–1012, 2012.

Ieee guide for the interpretation of gases generated in oil-immersed transformers, IEEE std c57.104-2008

(revision of IEEE std C57.104- 1991), pp. C1–27, 2009.

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