To prevent secondary damage caused by reclosing onto permanent faults in hybrid multi-terminal DC (MTDC) systems, a permanent fault identification scheme based on line commutation converter (LCC) signal injection is proposed. First, leveraging the fault control ability of LCC, an additional control strategy is applied to the LCC firing angle to realize signal injection. The frequency, duration and amplitude of the injected signal are analyzed and determined, and an LCC signal injection strategy is formulated. Secondly, the voltage difference after signal injection under different fault properties is analyzed using a distributed parameter model. It is found that due to differences in line models, there is a significant amplitude difference between the measured voltage at the local end and the calculated voltage at the remote end under different fault properties. Finally, a normalized area difference is constructed based on the above amplitude difference to realize permanent fault identification. PSCAD/EMTDC simulation results show that the proposed scheme utilizes single end data, is immune to data communication issues, requires no simulation-based parameter tuning, and can reliably identify permanent faults. It is capable of withstanding 400 Ω fault resistance and 40 dB noise interference, and is suitable for lines up to 1500 km in length.