power capacitor insulation cooling oil is a kind of liquid electrical insulation material. It is refined from petroleum through distillation. Its main ingredients are a mixture of various hydrocarbons . It is mainly composed of alkanes , cycloalkanes , aromatic hydrocarbons and alkenes . These molecules mainly contain chemical groups such as CH3, CH2, CH, etc., and some also form heterocycles with other elements. The carbon-carbon chemical bonds include C—C, C=C, and CthreeC. The composition of the gas generated by the capacitor insulating oil is mainly determined by the different characteristics of the chemical bonds of these hydrocarbon compounds. The main rules are as follows:
1) When the insulating oil is less than 140°C, evaporation and will slowly oxidize .
2) When the insulating oil is between 140 and 500°C, the oil decomposes mainly to produce CH4 and C2H6 alkane gases. When the temperature is greater than 500°C, oil decomposition increases sharply, and the growth rate of olefins and H2 is accelerated. When the temperature is greater than 800°C, C2H2 will also be produced.
3) The temperature is greater than 1000. C, most of the gases produced by oil cracking are C2H2 and H2, and CH4 and C2H4 are also produced.
4) When there is moisture, water and Fe will generate H2 under the catalysis of metal materials such as steel.
5) As the temperature increases, the order in which the cracking products appear is: alkanes, alkenes, alkynes . When there is some kind of fault inside the equipment, the energy generated may break the carbon chain of hydrocarbon , producing low molecular hydrocarbon gas or H2, CO, etc.
In summary, the dissolved gas monitoring group in the insulating oil of capacitor can be determined as H2, CO, CH4, and C2H6, C2H4, and C2H2.
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