Relationship Between Dissolved Gas in Oil and Transformer Faults

As we all know, transformer oil is an excellent medium that primarily serves the purposes of electrical insulation and cooling in transformers. When overheating and discharge faults occur inside the transformer, the oil and other insulating materials undergo chemical decomposition, producing specific hydrocarbon gases and H2, as well as carbon oxides.

The types, quantities, and production rates of these gases are often closely related to the fault temperature. Theoretical and practical evidence has shown that as the fault temperature increases, the hydrocarbon gases with the highest production rates are CH4, C2H6, C2H4, and C2H2. Most of these characteristic gases dissolve in the transformer oil, with a small amount rising to the surface and entering the gas relay.

Therefore, regularly measuring the composition and content of characteristic gases dissolved in transformer oil can help determine the degree of heating inside the transformer and identify the presence, nature, type, and severity of a fault by analyzing the temperature at the heating or discharge point. Here is an analysis and judgment guide for dissolved gases in transformer oil, explaining the relationship between characteristic gases, temperature, and fault categories:

General Overheating Fault of Transformer

Total hydrocarbons are high.
C2H2 is less than the attention value of 5 µL/L.
The fault is in the early stage, and the gas production rate is slow.

Severe Overheating Fault of Transformer

Total hydrocarbons are high.
C2H2 may be greater than 5 µL/L, but it has not yet become the main component of total hydrocarbons.
H2 content is high, and the gas production rate is fast.