For Flexible Medium-voltage DC distribution grid, this paper proposes a traveling wave bus protection and a fault pole selection method. The method is to extract the polarity relationship of current traveling wave in each branch of the bus by wavelet transform, it distinguishes the internal and external faults and chooses the fault pole by comparing the polarity of positive and negative poles of modulus maxima. The simulation and verification are based on three-terminal DC distribution network model established in PSCAD/EMTDC software. The simulation results show that the bus fault identification and pole selection method are not affected by factors such as noise interference, fault resistance and control mode. It can identify internal and external faults of DC bus reliably and rapidly.

traveling wave,bus protection,fault pole selection,wavelet transform,DC distribution network