DC de-icing technology is the key technology for solving ice-cladding problems of high voltage and extra high voltage transmission lines. The protection principles and scheme of DC de-icer is the key technology of ensuring safe and reliable operation of the ice-clad transmission lines and system. The DC de-icing system and its protection configuration is described. The inadequacy of the selectivity of overcurrent protection are pointed out. Based on an in-depth analysis of the fault characteristics of the converter and the converter transformer of the DC de-icer

a new measure to ensure the reliability and selectivity of the overcurrent protection for DC de-icer is proposed. PSCAD/EMTDC simulation software is used to simulate and test all kinds of faults

which has verified the validity and correctness of the new protection strategy. This work is supported by National Natural Science Foundation of China for Excellent Young Scholars(No. 51422703).