Research on Differential Protection of Low-frequency Transmission Lines Based on Sampling Value Differential

In case of a failure within the area of flexible low-frequency transmission lines, the power electronic devices (M3C) at both ends of the line limit the fault current, which causes the reduction of sensitivity of the traditional phasor-based line differential protection or even failure to operate. Based on the structure of a flexible low-frequency transmission system, the electrical characteristics of the line failures were analyzed, and a differential protection technology suitable for flexible low-frequency transmission lines was proposed based on the differential principle of sampling values. The low-frequency transmission line model was built in RTDS, and the method was verified to meet the protection requirements of flexible low-frequency transmission lines.