The hybrid HVDC system, in which the rectifier is made up of LCC and the converter is composed of MMC, has quite different characteristics from the symmetrical LCC-HVDC systems. Therefore, it is necessary to study the protection method for hybrid HVDC transmission lines. This paper develops a reduced analytical model of LCC-MMC-HVDC system for DC line fault transient analysis. The analytical models of internal and external fault are established in frequency domain and applicable to the first fault traveling wave. Analysis illustrates that it has high accuracy compared with the simulation result. Based on the reduced model, the analytical setting method of traveling wave protection is put forward, which considers the randomness of sampling. Furthermore, the performance of traveling wave protection is analyzed based on the analytical analysis, and the result shows that traveling wave protection performances poorly when the fault resistance is high.

hybrid HVDC system,fault analytical analysis,initial fault generated wave,traveling wave protection