Parameters for Transformer Oil 1

[sunilji]

Hi Again ! I need help with the following query :
What are the benchmark values for Transformer Grade oil?
I have a testing report ( Dissolved Gas Analysis ) that states the values of Hydrogen,sulphides etc. The lab people insist on a second test to find out the differential values before coming to a conclusion.I am interested to know if there is a set of standard values for dissolved gases.The transfomer in question is a 1000kva, 11Kv/433V Distribution Transformer

 

[jnims]

There are several resources you may use to evaluate the results of this test:

ANSI/IEEE C57.014 Guide for the Interpretation of Gases Generated in Oil-Immersed Transformers.

S.D. Myers, A Guide to Transformer Maintenance.

Both cover some of the ratio methods for identifying the type of events. They also give indications of significant concentrations.

By the way, testing again after six months or a year can be a valid conclusion.

 

[jbartos]

Suggestion: Visit

http://www.udeyraj.com/udey/Oil Test Set.htm

http://www.designergraphix.com/eltel/p4-transfoil.htm

http://www.harristestinglab.com/c14.htm

http://www.morganschaffer.com/

http://www.setransformer.com/quality.html

http://www.morganschaffer.com/labfuran.htm

http://www.hydracen.com/dx/toainfo/toainfo.htm

etc. for more info

 

[rajdev]

send me the report and other values and i will
try to interpret the results. send the values either
raj_dev@excite.com

 

[stevenal]

The lab is right. You need to see rate of change to get meningful results.

 

[electricpete]

A trend over time is the ideal situation as mentioned. BUT
IEEE C57.014 does give criteria for classifying the transformer from condition 1 (normal) through 4 (really bad) based on DGA values in a single sample. It'll also provide some discussion to focus you in on what the problem might be. For instance: Hi CO and CO2 - generally thermal overheating. Hi C2H2 - generally arcing. It gets much more involved than just looking at one gas. The standard also provides flowchart for applying the Roger's ratio and Dorenburg methods.

 

[rajant]

H2 value alone is not indication of any fault. You have to follow test again to see variation in H2 and other DG. Presence of increased value of Methane, ethane, acetylene with presence of H2 indicates some causes like PD, overheating or arcing. <500ppm/vol of H2 is is considered normal. Again Other factors, ratio of CH4/H2 can be considered 0.1<r<1 for normal.

 

[PowerSaudi1]

The concern in DGA test results is not only the ppm of gases. The more important factor is the Trend of gases. Please let me know the results with ppm figures.

I

 

[jbartos]

Small suggestion: Visit

http://www.usbr.gov/power/data/fist/fist3~30/3~30_4~4.htm

http://www.usbr.gov/power/data/fist/fist3~30/3~30_4.htm

for more info on DGA

 

[electricpete]

jbartos - that's a pretty good link. From what I can tell it contains verbatim almost the same info as the IEEE guide, including the limits for classifying levels 1-4 metnioned above.

 

[cshro]

Here are two almost same standards

http://ieee.org/

(IEEE Std C57.104-1991)

http://www.iec.ch/

(IEC 599)