No.

Gases Detected in Oil Sample

Fault Interpretations

1

Nitrogen plus 5% or less oxygen

Normal operation

2

Nitrogen, carbon monoxide, and

carbon dioxide

Transformer winding insulation overheated;

Key gas is carbon monoxide CO

3

Nitrogen, ethylene, and

methane―some hydrogen and ethane

Transformer oil is overheated; minor fault causing oil breakdown. Key gas is ethylene C₂H₄

4

Nitrogen, hydrogen, small quantities of ethane and ethylene

Corona discharge in oil;

key gas is hydrogen H₂

5

Same as 4 with carbon dioxide and carbon monoxide

Corona involving paper insulation;

key gas is hydrogen H₂

6

Nitrogen, high hydrogen and acetylene; minor quantities of methane and ethylene

High-energy arcing;

key gas is acetylene C₂H₂

7

Same as 6 with carbon dioxide and carbon monoxide

High-energy arcing involves paper insulation of winding; key gas is acetylene C₂H₂