Transformer oil sampling : LUSENET : Commercial and Industrial Transformers : One Thread

We use outside service to conduct oil sampling on over 200 transformers. There telling us to resample in 6 mths due to gas content. ? Will the gas level decrease in transformer oil samples in 6 mths. Is there a level of gas content when oil should be changed. If we know we have a gas level why retest. What hazards involved in transformer samples with gas level in transformer oil.

-- Tim Inman (, July 18, 2001


Tim, Thanks for your interest in the transformers bulletin board. I apologize for taking so long to respond to your question about Transformer Oil Sampling. The best person to contact for this information is the manager of transformer technology at Square D Groupe Schneider, Phil Hopkinson. You can reach Phil by phone (704) 282- 7469 or by e-mail at If you still have questions after speaking with Phil, please let me know and I will direct your questions to the appropriate party. Thanks again.


Melissa Mastrianni CEE

-- Melissa Mastrianni (, August 23, 2001.

Three types of tests on done on Xfmrs for Preventive maintance, Condition Assesment or Internal Faults.

Dielectric Fluid Quality (Oil Screens): (Yearly Test) Dielectric Strength, visual Condition and Water being the Critical Tests. Color, Neutralization (acidity) and IFT (Interfacial Surface Tension) indicating Oxidation of the Oil.

Furans: The "apparent age" based on the Degree of Polymerization (DP) of the paper (done every 2 to 3 years)


Dissolved Gas Analysis (DGA, Fault Gas): Looks for gases in oil that are formed as a by producting of heating of the fluid and heating of the cellulose insulation. Specific gases are produced by a range of temp. and these temp. are indicative of specific types of internal faults.

What is look at in DGA testing: Specific gases and there PPM level in the fluid, the ratios or the gases and MOST IMPORTANT...increases and rate of formation of each gas and the TCGs.

If you would fax some of your test results to me for review, I'd be happy to educate you on what the tests mean and give a fault analysis.

Mel Wright Lab. Mgr. GE Liquid Insulation Lab (transformer oil lab) Phone 303-329-2350 Fax 303-329-2322

-- Mel Wright (, November 06, 2002.

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