Arc discharge within a transformer oil tank can cause rapid thermal decomposition of a large amount of transformer oil

producing gas in a short period. The subsequent pressure wave propagation and superposition process may lead to the rupture of the oil tank and the occurrence of fire and explosion accidents. Based on thermodynamic theory

this paper investigates the calculation method for gas production from insulating oil decomposition under arc conditions. By utilizing the temperature dependence of the chemical equilibrium constant

the arc channel in the insulating oil is divided into two regions

namely

the core zone and the fringe zone. The chemical equilibrium characteristics of the thermal decomposition reactions of alkane molecules within each region are analyzed separately. In the fringe zone of the arc

the relationship between arc energy and decomposition reaction enthalpy is quantitatively characterized through establishing enthalpy change equations

and an equivalent thermal decomposition temperature range of 487~1 497 K is obtained. Moreover

in the core of the arc

the complete thermal decomposition of oil under extremely high temperatures is taken into conderation

and the chemical equilibrium constant(K=105) is employed to calculate the gas production characteristics resulting from the thermal decomposition of oil. Finally

butane and propane are used as examples to calculate for three actual arc energy

and the computational validity of the proposed methodology is verified by using the improved IEC ratios to output the types of faults associated with the gas generation.