In order to explore suitable dissolved gas analysis（DGA） method for natural ester insulating oil

the dissolution properties of characteristic gases in nature ester insulating oils need to be studied. So dissolution properties of characteristic gases in 3 kinds of nature ester insulating oils（including FR3

?

nature ester

Refined soybean insulating oil

and Methyl rapeseed insulating oil）were studied with a kind of mineral insulating oil as a reference. The Ostwald equilibrium constants（K） of seven kinds of fault diagnosis characteristic gases（including H

2

CO

CO

2

CH

4

C

2

H

4

C2H6

and C

2

H

2

） in the four kinds of insulating oil were measured at various temperatures（θ） between 30 ℃ to 70 ℃. Through the Ostwald equilibrium constant（K） and temperature（θ） matching

28 groups of K-θ model equation of the seven characteristic gases in the four kinds of insulating oil were established

and the other K could be calculated according to temperature of some characteristic gas in some kind of insulating oil. Through comparison of the characteristic gases K-θ curve in the same kind of insulating oil

hydrocarbon gases solubility in four kinds of insulating oil in size order can be found as follows: K（C

2

H

6

）>K（C

2

H

4

）≈K（C

2

H

2

）>K（CH

4

）

non hydrocarbon gases solubility in size order as follows: K（CO

2

）>K（CO）>K（H

2

）.