Dakshin Lab Agencies


	What is Dissolved Gas Analysis (DGA) of Transformer Oil? DGA of transformer oil is the most sensitive and reliable loss prevention technique to have early indication of abnormal behavior of transformer.
	How is the DGA related to health of transformer? Transformer oil is the ‘blood’ of transformer. It bathes every component of transformer and contains lot of diagnostic information to evaluate health of transformer.
	What is the diagnostic information? Cholesterol or sugar levels in ‘blood test’ reveal health of a man, whereas concentration levels of ‘fault gases’ indicate condition of transformer’s health.
	What are ‘fault gases’? ‘Fault Gases’ are formed in transformer oil due to natural ageing and as result of faults inside transformer. Gas formation includes oxidation, vaporization, insulation decomposition, oil breakdown and electrolytic action. The gases are Hydrogen, Methane, Acetylene, Ethylene, Ethane, Carbon monoxide and Carbon-di-oxide.
	What are the important steps of DGA? The three important steps are, Transformer Oil Sampling using Oil sampling tube. Complete extraction of fault gases using Multiple Gas Extractor. Quantitative determination of fault gases and analysis.
	Which are important parameters for correct results? Transformer oil is to be sampled, transported, stored and the faults gases are extracted, without any lose to its gas contents. Complete extraction of all gases from oil is to be ensured since the results are interpretation of concentration of fault gases in sample oil.
	How are the DGA results interpreted? DGA results are interpreted in PPM (parts per million). They represent concentration of fault gases in sample oil. To achieve this, fault gases are completely extracted from a known volume of sample oil. The concentration is observed in ‘millilitre of gases per millilitre of oil’ Then converted into ‘microlitre of gases per litre of oil And again converted into ‘microlitre of gases per microlitre of oil (OR) parts per million Hence for accurate results ‘complete extraction’ is important.
	Does gas extraction done in ‘Single Extraction method’ represent all the dissolved gases? No, it does not represent. In single extraction method, it is only a ‘partial extraction’ with efficiency of less than 50% and some of the low soluble gases, like carbon monoxide, are not detected.
	Are the results obtained from ‘Single Extraction’ for individual gas concentrations correct? No. In single extraction, it is only a partial extraction of fault gases. Since the fault gases are dissolved in oil at different concentrations depending on their solubility, the results are misleading.
	How to extract all the dissolved gases and obtain their concentrations accurately? CPRI, Bangalore designed a novel method in 2004 and Dakshin Lab Agencies has developed it into a unique ‘Dakshin Multiple Gas Extractor’ D-TOMGET, in which the same sample oil is exposed to high vacuum repeatedly until complete extraction of dissolved gases is ensured.
	What are the different types of DGA? Vacuum Extraction Method called Toepler pump method using Mercury piston. This method alone represents all the dissolved gases in its accurate concentrations. D-TOMGET and D-GASOIL are based on this method. They are simple and cost effective. The Stripping Method: Nitrogen is allowed to flow through the sample oil as a carrier gas. Efficiency of the method is very much limited and the system is more complicated. Head space analysis: Argon is used as blanket in a vial of sample oil and agitated. Accuracy of results depends on various factors like precise volume of oil and blanket gas, apart from temperature and pressure.
	Do you have different models of gas extractors? Yes. We do. You can choose them according to your budget. D-TOMGET , Model – 1207 : The most efficient system for DGA. D-GASOIL, Model – 309 : Simple and Manual multiple gas extractor Single Extraction Method: Partial extractor and obsolete method.
	What are the important specifications followed in D-TOMGET or D-GASOIL, and insisted by IS:9434:1992, ASTM D -3612 – 02 and Central Power Research Institute (CPRI)? D-TOMGET or D-GASOIL, if subjected to a vacuum of 0.1 mbar and left, the vacuum remains unchanged. Gas Expansion Chamber is ten times the volume of sample oil for complete extraction. Extraction is done at a very high vacuum of 0.02 mbar Sample oil can be exposed to vacuum many times, until complete extraction of fault gases is achieved. Measurement of extracted gases shall be possible to the nearest 0.05 ml at atmospheric pressure.
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