Due to the wide acknowledgement of renewable power sources (RES), such as wind power and solar power, the HVDC network has been accepted as an promising solution for connecting them into the AC system. Furthermore, in order to enhance the flexibility of whole power system, imbedding the RES into one system attracts interests from both industry and academia, i.e. establishing multi-terminal HVDC (MTDC) network. Unlike the conventional point-to-point (p2p) system, the responses of MTDC system after faults differ under different control modes, network topologies, and protection methods. Especially, the travelling wave of fault-incident surge can propagate the whole system in several milliseconds, which brings challenges to the system operation. The research aims at analyzing the transient behaviors based on typical system configuration and modelling method, and establishing a reliable MTDC system protection methodology.