Abstract: In view of the fact that the transient electrical quantities in doubly-fed wind farms cannot be accurately analyzed, leading to the issue of incapability of traditional protection methods in correctly identifying the fault location and acting accurately, a longitudinal protection method is proposed for doubly-fed wind farm transmission lines based on power modulus component in frequency domain. Firstly, by integrating the wind turbine model with the topology of the wind farm network and considering the different characteristics of voltages at the terminals of each connected wind turbine on the collector line, the frequency-domain modulus component of the short-circuit current sent by the wind farm is calculated. Consequently, a frequency domain equivalent model for the fault in a doubly-fed wind farm is established. On this basis, combined with the topology changes of the fault network inside and outside the area, we select a one-modulus component to construct a protection criterion for the sum of output power at both ends of the transmission line. Finally, simulation is conducted on the RT-LAB platform to validate the capability of the proposed method in this paper in accurately distinguishing faults inside and outside the zone. Additionally, it exhibits good resistance against transition resistance, remaining unaffected by fault location.