[Gajjala Sreelatha]

In one of our transformer 100 MVA, 220/132 kV Auto, only Hydrogen generation is increasing, other fault gases are absent.
In one of our transformer 100 MVA, 220/132 kV Auto, only Hydrogen generation is increasing, other fault gases are absent.

The oil used in the transformer has a very low aromatic content less than 2%. Is this the cause of H2 generation?

can any body answer this question please?

Topic

[Hamid]

In lowest temperature fault conditions the hydrogen generation is possible, of course it is with other hydrocarbon radicals; because the hydrocarbon molecule breakdown without new produced material containing carbon atom in related temperature is impossible. The identification and significance of gases in electrical equipment was first used to distinguish between combustible and non-combustible gases produced in transformers as long ago as the 1920s. This was carried out by applying a light to the gas collected from the sample or vent tap of the Buchholz relay. Transformer Oils consisting of high molecular weight hydrocarbon molecules can suffer degradation due to decomposition of these molecules into lighter more volatile fractions. This process is also accelerated by temperature. It is desirable that it should not occur at all within the normal operating temperatures reached by the plant, but it cannot be prevented at the higher temperatures generated by fault conditions. Initially the procedure aimed to detect the presence of hydrogen, which meant that there was a

[Gajjala Sreelatha]

Dear Sir, Thank you very much for your reply. This is well understood. But my question was whether due to less aromatic content in oil (less than 2%) the oil in this case is unstable and its gassing tendency is negative and is not absorbing hydrogen produced. Is it a case od OD? But CH4 is absent also cellulose involvement is not there. H2 is increasing nearly at the rate of 35ppm per day. Should we take shutdown but what to look for? Sreelatha.G

[bob o]

Get EA technology in. Get them to do partial discharge testing

[Hamid]

Dear Bob, Please more explain, we will glad and appreciate to hear about your experience. Best Regards Hamid

[bob o]

Hamid, it seems you may have a low level fault. You need to carry out some testing. If you do not want an outage you could try partial discharge testing to see if there is any discharge/ insulation problems within the transformer. What hydrogen levels are in the tapchanger? Is there any gasses building up in the bucholtz? Eventually if the problem persists you will have to have an outage to carry out some testing. Regards

[Sreelatha]

Dear Sir, Thank you very much for your reply. If there is PD, Methane should have also come and CH4/H2 should have been < 0.2 as per IEC. If there is leakage from OLTC compartment to main tank, other fault gasses potentially C2H2 should have shown. There are no gases at present building in Buchholz relay. We have analyzed chemical composition of oil. Aromatic compounds are 1.3% less than 4% min as per IEC. Is low aromatic content the cause of H2 generation? Is the gassing tendency of oil creating issue? Is this a case of stray gas (H2) generation? What to look for if transformer is opened? Regards Sreelatha

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