Frequency domain spectroscopy(FDS) is widely used to evaluate the quality of oil-paper insulation. Accurately modeling the triangle insulation of oil-immersed inverted current transformers

which is a critical fault-prone area

is essential for linking FDS results with insulation performance changes. To develop a more precise FDS computational model

this study employed Bézier curves to geometrically describe the triangle insulation and used the X-model to calculate the complex capacitance of the main insulation. A three-dimensional finite element simulation was also conducted to obtain the transformer’s complex capacitance. The proposed model’s accuracy was verified by comparing the measured complex capacitance of three oil-immersed inverted current transformers from different manufacturers with results from the FEM and Bézier-curve-based models. Experimental results showed that the average relative errors were less than 5.489% and 10.385%

respectively.