Abstract: Aiming at the existing 100 Hz protection using only a single device measurement information for fault judgment,the action response of the protection is blind to a certain extent,and its adaptability is insufficient when the AC area of converter station fails. It is proposed to distinguish the DC area fault from the AC area fault of rectifier station based on station domain information,which realizes 100 Hz protection optimization and gives 100 Hz protection the ability to identify the DC area fault and the AC area fault of rectifier station. Based on the cause analysis of misoperation of 100 Hz protection,the correlation coefficient between the negative sequence voltage of converter bus fundamental frequency and the second harmonic voltage of DC line is proposed,and the fault area identification method of rectifier station is constructed. The simulation results show that the method is not affected by fault type,fault location,transition resistance,fault initial angle and noise interference,and has high reliability.