A Differential Protection Method for Submarine Cables Based on Transient Frequency Characteristics

Due to the high capacitance of submarine cables and the integration of inverter-based power sources from offshore wind farms, traditional power-frequency-based protection methods face severe challenges in sensitivity and operating speed. This paper proposes a new transient-based differential protection method for submarine cable lines, based on the waveform characteristics of the fault component’s transient differential current. The method uses the Prony algorithm to extract key frequency information from the transient current and utilizes the significant difference in the frequency characteristics of the differential current between internal and external faults for discrimination. The research finds that during an external fault, the differential current of all phases exhibits high-frequency oscillations, whereas during an internal fault, the faulted phase’s differential current frequency is close to the power frequency, while the unfaulted phases show high-frequency oscillation characteristics. Verified by PSCAD/EMTDC simulation results, the proposed protection principle requires only a 5 ms data window to quickly and reliably identify internal and external faults, effectively improving the protection’s operating speed and demonstrating high practical value.