Abstract: The internal short-circuit faults of extra-high-voltage converter with large oil filling can produce high-energy oil arc, accompanied by great mechanical impact and a large amount of high-temperature and high-pressure oil gas, which can easily lead to structural tearing of the tank and explosion. By paralleling a high pressure SF₆ gap triggered by plasma injection at the grid side of the converter, a low-resistance gas arc channel can be formed after gap conduction within 1 ms, which is expected to realize the rapid transfer and extinguishment of arc in oil. By using this method, the traditional fault clearing time can be reduced by 80%. The feasibility of current transfer in oil is affected by the characteristics of the fault arc, whereas, the related research is mainly carried out for the short oil gap (a few millimeters to tens of millimeters) with small current, the arc characteristics in oil with long distance and high energy is still not clarified. Therefore, we equivalently simulated the internal discharge faults of the converter, designed a test circuit, test methods, an arc-firing simulation device, and a high-precision measurement and control system, and successfully carried out the tests of arc transfer and extinguishment under six different parameters. The results show that the SF₆ triggering gap can realize the rapid transfer and extinguishment of the arc in oil, with 250~650 mm and 10~50 kA, within 1 ms. The minimum initial arc voltage of the oil gap is more than 10 kV, and the arc voltage of unit length increases slightly with the increase of the oil gap length. The arc voltage is slightly affected by the amplitude of short-circuit current. This paper verifies the feasibility of the technology scheme of transferring and extinguishing the arc by high pressure SF₆ gap, and verifies the effectiveness of the design of the explosion protection gap, which provides a potential technical route for the explosion protection of UHV converter transformer.