Magnetic flux caused by high current in voltage regulation leads of large capacity converter transformer will generate loop current in the closed loop of the structural parts. If the loop current is too high

overheat will be caused in the structural parts

which will affect the safe operation of converter transformer. Consequently

we analyzed the cause of theloop current

and introduced countermeasures to prevent the loop current. Taking a ±800 kV converter transformer as a research subject

we theoretically analyed and calculated the loop current;meanwhile

we numerically simulated and calculated the loop current by establishing a complete leakage magnetic model of converter transformer. During the temperature-rise test of converter transformer

loop current was measured by an optical fiber current sensor. According to the test results

the accuracy and feasibility of theoretical analysis and numerical simulation were verified. The research method adopted in this paper can be used to calculate the loop current of structural parts of converter transformer and high-current devices in actual projects

which has a guiding significance for the design and safe operation of converter transformer and high-current devices.