Abstract: In the frequency conversion system, due to the existence of the frequency converter, a large number of high-order harmonics and high-frequency pulses will be generated, which will create a zero-sequence current on the ground capacitance of the power system transmission line. In severe cases, it will affect the accuracy of the leakage detection process and the misoperation of the leakage protection system. Therefore, after analyzing the disadvantages of the existing methods, this paper proposes a fast complete ensemble empirical mode decomposition(FCEEMD) method, and applies it to the leakage detection by combining it with the Prony algorithm. This method can not only effectively make up for the shortcomings of the traditional Fourier analysis method, but also can better meet the real-time and accuracy requirements of the leakage protection system, and its reliability and practicability are verified by simulation experiments.