Recently multi-terminal HVDC system (MTDC) has become a competitive alternative for inter-area large power transmission. The Kunbei-Liuzhou-Longmen (KLL) MTDC project promotes MTDC practice to ultra-high voltage level. It is composed of one LCC (Kunbei) and two VSC (Liuzhou, Longmen) converter stations in parallel, the operation mode of the system is flexible. And in the process of fault clearing and recovery, control coordination among three converter stations is needed. Thus, the conventional control and protection system for bi-terminal HVDC and the associated special protection scheme (SPS) cannot be directly adopted in KLL multi-terminal HVDC. This paper first introduces the MTDC line fault recovery (DCFR) and converter station online disconnection (CSOD) of KLL MTDC that used in system analysis, and the frequency response characteristic of the sending end AC system when it suffers a significant power imbalance. Then, the impacts of DCFR and CSOD and the corresponding SPS are studied and verified by transient stability simulation using real operational planning data. The study provides a reference for the SPS design of KLL MTDC and other MTDCs.