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.
THANK YOU
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