Reliable fast fault detection and location provides important theoretical support for large-scale development of dc distribution grid without dc circuit breaker. The present protection is not fast enough to meet the requirements of safe and stable operation in the dc distribution grid. The key development of this paper is to adopt an ultra-high sampling rate to obtain the broadband information of the fault-induced travelling wave and to distinguish the internal or external fault through multi-resolution analysis. It is found that pole-mode travelling waves always appear when faults occur on the dc line but do not exist when faults occur outside the line because of the smoothing reactor. Using the initial fault-induced traveling wave, the method proposed in this paper is the quickest theoretically. Then the fault segment can be immediately identified according to the polarities of the two-terminal traveling wave. Later the fault is precisely located based on the time difference of initial travelling wave. Next, based on the typical topological structure of the dc distribution grid without dc breaker, the ultra-high-speed travelling wave based protection scheme is proposed. At last, simulation results confirmed the theoretical analysis.