Oil furan Level standards (test ASTM D5837)

[Gauss2k]

I just received an oil analysis result for a transformer. The report included the level of furan, according to the test "ASTM D5837".

I was able to find several references for the standard values from the IEEE and other sources for the dissolved gases (for each gas and for the several ratios), physical properties of the oil, water content, etc, but I just can't find anything about the furans.

The only thing I know is that the main goal of furan testing is to determine whether the paper in a given transformer has been or is being damaged by heat.

If the level of the CO/CO2 is high but the furan level is low, should I worry? I saw many references where they said that a high CO/CO2 ratio was a good indication of isolation damage.

And what if the furan level was high (and what is a "high level" of furane anyway??), what conclusion can I make?

 

[miketech59]

The insulation in a transformer is made up of cellelouse .When this degrades furans are given off and retained in the oil .There are five types of furans and the trending of these furans and their ratio gives an indication of the state of decomposition of the insulation . The furan test is a noninvasive test to determine the Degreee of Polymerization (DP) of the insulation. In some literature is it said that when the DP reaches 200 the insulation ( the transformer ) is at the end of its useful life .
The high ratio of CO/Co2 just means that you should have a a furan analysis done on the oil which you will need to trend since a once shot does not give an accurate picture .

 

[unclebob]

I once asked Morgan-Shaffer Laboratories that question. They
told me that a total value of 100 ppb or higher is considered to be 'high'. They were hesitating about telling me that information. They don't want to be involved...

 

[jnims]

There is not consensus on the level of furans that indicate a transformer is at the end of its useful life. I have seen values quoted from 100 ppb to 4000 ppb. When trying to make comparisons, it is important to know if the paper insulation is thermally upgraded (typical in North America) or not. Also, know if you are looking at the total concentration or just 2-FAL. Concentrations of 2-FAL are more stable in an operating transformer.

A paper by SD Myers took a statistical look at their database of test results. Some of their conclusions were total concentrations above 1000 ppb indicated a transformer in poor condition (but could benefit from processing the oil) and total concentrations above 2500 ppb indicate a transformer will need to be rewound. Levels above 2500 ppb do not necessarily mean it should be taken out of service, but than mechanical strength against short circuit forces is questionable.

One additional note. If the transformer oil has been reclaimed, this process will greatly reduce the furan concentrations initially, but levels will increase and stablize at a value less than the original. Making strict comparisons to some fixed threshold will be difficult without full knowlegde of the transformer's history.

 

[miketech59]

Lets try the theory again . A new transformer is at 100 % useful life with an estimated DP( degreee of polymerization ) of 800 ( DP=800) and if the insulation is the uninhibited type a 55C rise transformer one of the furans called 2FAL will be 58 ppb( 2FAL=58).When the insulatioon reaches the end of its useful life the ( DP=200). At this stage the 2FAL count would be 5,315ppb . ( 2FAL=5315)
What needs to be done is to trend the furan with the DGA . At 100ppd the insulati9on has sustained some damage but with proper care ( drying out of the insulation, etc) you can have many more useful years . Please check the Transformer Maintainance Institute , SD Myers for more information.

 

[PowerfulStuff]

Gauss2k,
Another possible cause for the inconsistency is whether the insulation aging is a bulk or point phenomena. Rapid deterioration in a small section might give the gas ratio without a corresponding change in furans. I've been comparing furan results against paper samples for transformer that have been overhauled in my workshop and the correlation is fantastic. There are remote paper sampling systems which allow paper samples to be taken without opening up a transformer - this way you can make important decisions with as much information as possible.

Regards,
PowerfulStuff