What is the Difference Between Furan and DGA

Furan is the name of a chemical. Actually you have to explore the word furan analysis. Chemical structure of furan is given below.

In case of solid insulation of transformer due to ageing to faults that is happening inside the transformer this insulation will be degraded into some chemicals. In that furane is also included. So measured value of furane is a good indication for tranformer insulation. For this analysis first we have to extract the furane then it is measured.

If furane content ids high it means transformer oil to be changed otherwise it will lead to breakdown. Acceptance level of furane is given below

0-100 parts per billion = Acceptable
101-1000 parts per billion = Marginal
Greater than 1000 parts per billion = Unacceptable

DGA is related to liquid insulation, that is transformer oil. Due to faults that is happening inside the transformer heat will be formed and due to this energy the long organic oil chain is getting broken. As a result so many gases is formed such as CO2, C2H4, C2H2, C2H6, C3H6, C3H8, CH4, CO, H2, O2, N2 etc. The analysing of this gases is a good indication of transformer oil insulation value as stated above case.

For the analysis first we have to extract the gas from the oil. For this various methods are using (eg: head space extraction, polymer membrane separation & vacuum degasing). Important is maximum extraction of gas from oil. Vacuum degasing is the most modern method that giving around 100% of gas extracton.

Second stage we have to analyse this gases for that we need to know the exact amount of each gas. For this recently two methods are using. 1) Combintly flame ionisation detection and thermal conductivity detection 2) Photo accoustic spectroscopy.

After the measurement this results are analysed using Roger method, duval triangle method or ASTM/IEC 61181 standards.

Along with furan five most prevalent derivatives of furan that also arises from the degradation of the cellulose and that are soluble in the oil to an appreciable degree are the following: 2-Furaldehyde, Furfuryl alcohol, 2-Acetylfuran, 5-Methyl-2-furaldehyde, and 5-Hydroxymethyl-2-furaldehyde.

Acceptance level of furane was clearly specified in the answer

0-100 parts per billion = Acceptable
101-1000 parts per billion = Marginal
Greater than 1000 parts per billion = Unacceptable

Furans are a direct indication of the rate of degradation of the paper insulation within the windings of the transformer. As the cellulose chain in the insulation breakdown furans are released into the oil.

Having a high level of Furans does not mean you need to change the oil in fact you should be monitoring those levels over time to see what the rate of increase is. This will give a good indication of the remaining life of the transformer.

If key gases in the DGA levels are high then again investigate the source as they act as markers for things that are going wrong inside the unit. Again changing the oil only masks the problem it does not elliminate it.

When you fix the problems then you refurbish the oil (or replace) and soon after take another oil sample for testing, eg 2 weeks then 3, 6 & 12 months so that you can see that you have either solved the problem or it is still there.

When you do that make sure the historical data is not lost but is tagged as having been altered by the work done on the unit.

Try a Google search on Furans in Oil - you will get some very interesting papers.