Abstract: Research and application progress of NARI-RELAYS in protection based on DPFC were reviewed, key technology employed in line, busbar, transformer and generator protection were presented. It was pointed out that integration of main and backup protection in one device and duplicate allocation was reasonable and beneficial. Key words: Protection; DPFC; Main protection; Backup protection; Duplicate protection 关键词：Research 0. Introduction Electric power network in China has step into a new stage with large-scale networks, super power plants and high-rating generators. By the end of year 2002, total installed generation capacity is 353000MW, total length of 35kV and above transmission lines is 806500kM, total installed transformer capacity is 1194000MVA, and generated energy of the year is 164
