Fast Protection Method for Low-Frequency Transformers Based on Instantaneous Phase Difference

Low-frequency transformer is the key equipment in the low-frequency transmission system of offshore wind power, and its fault characteristics are significantly different from those of conventional transformers, so the traditional transformer protection scheme is not applicable to this system. In order to solve this problem, this paper proposes a fast protection method for low-frequency transformers based on instantaneous phase difference. The method firstly utilizes the amplitude of differential current as the criterion for protection initiation, and then combines the characteristics of the instantaneous phase difference of low-frequency transformers under different operating conditions to construct the corresponding protection criterion. Finally, a simulation model of the low-frequency transmission system is constructed using PSCAD, and the proposed protection scheme is verified based on this model. The simulation results show that the method can act reliably during low-frequency transformer faults and has good protection performance.