Abstract: A new single terminal protection that extracts the amplitude characteristics of the high frequency band of the DC line fault current through a generalized S-transform is presented to overcome the defect of traditional HVDC transmission line protection.That problem is where the single terminal relaying cannot differentiate between internal and external faults.The research shows that when the DC line equipped with a hybrid DC circuit breaker fails,the transverse current difference of sampling frequency from 1000 Hz to 2500 Hz is obviously smaller when the external fault occurs than when the internal fault occurs.Fault criteria are established.The current amplitude of the characteristic frequency of the fault pole is greater than that of the non-fault in the case of single pole-to-ground fault.The current amplitude of the characteristic frequency of the two poles is approximately equal when a two poles short circuit occurs.The fault starting and pole selection criteria are built using a characteristic frequency from 300 Hz to 1000 Hz.On the RTDS simulation platform,a three terminal flexible HVDC system model of wind-solar-storage hybrid power generation station transmitted through HVDC is built.The simulation results show that the fault type and area can be identified rapidly and reliably.The effectiveness of the proposed DC fault ride-through scheme based on a hybrid DC circuit breaker is verified using an RTDS simulation experiment.