According to a special cross-country fault occurs on certain 220 kV transmission lines， this paper calculates the fault components of current and voltage and analyzes the performance of line protection based on the method of equivalent current and sequence component. The analysis results agree with the protection operation reports and recorded data， which shows that the conventional protection may select the fault phase wrongly and may refuse to operate when the cross-country fault occurs. According to the performance of protections with different principles， this paper presents the configuration scheme for the parallel lines on the same pole.