In recent years

there have been multiple accidents in China where oil immersed transformers have experienced internal pressure rise and tank rupture due to arc faults

posing a serious threat to the operation of the power grid and personnel safety. The rapid gasification of electric arcs and the high-temperature gas generated by the cracking of insulating oil are the main causes of internal overpressure; however

the in-depth research on the gas generation characteristics of arc faults is rarely available in the literature. Therefore

we established an experimental platform for power-frequency arc discharge in oil

explored the influence of current amplitude and arc length on the gas generation characteristics of arc in oil

and conducted research on the gas generation characteristics of arc in different stages. The experimental results show that the arc current amplitude has a small effect on the quantity of generated gas per unit of energy

whereas an increase in arc length increases the quantity of generated gas per unit of energy and significantly increases the arc energy

thus leading to a surge in pressure. During the arc discharge process

the insulating oil is relatively fullly cracked

and H2

C2H2

CH4

and C2H4 are the main cracking products. The arc current amplitude has a small effect on the gas composition. The cracking gas composition at 35 mm arc length is about 64%H2

21.1%C2H2

7.5%CH4

6.5%C2H4

and 0.9% other gases

and an increase in the arc length leads to a slight increase in the H2 content. During the arc discharge process

the H2 content tends to gradually decrease to a stable value due to the influence of temperature and pressure inside the bubble. The results of this paper lay an important foundation for the next step in the characterization of arc pressure in oil.