Abstract: Flexible low-frequency transmission technology combines the advantages of both power frequency transmission and direct current transmission, and has potential application in scenarios such as offshore wind power transmission, renewable energy collection, and flexible interconnection of urban power grids. There are severe transient overvoltages of flexible low frequency converter station after faults and subsequent blocking process, which affects station parameter design and insulation fit. In this paper, an overvoltage simulation model is established for the typical topology and parameters of the flexible low frequency converter station, and a simulation study of the transient overvoltage after a typical fault is conducted. Based on the characteristics of overvoltage generated after faults, the process after faults is divided into four transient processes, and the overvoltage characteristics and causes of different positions in each process are analyzed. Different fault conditions and corresponding protection strategies are taken into consideration, and the maximum transient overvoltage level of main positions and equipment in the converter station is simulated and calculated. Moreover, the arrester configuration and parameters of converter station is proposed, and the suppression effect on transient overvoltage is verified. The results show that there are transient overvoltages in the converter station generated in the four transient processes of fault occurrence, converter control response, converter blocking, and breaker disconnection. The overvoltage level in the transient process of converter blocking is the highest. When the suppression is not taken into consideration, the transient overvoltage level in the 220 kV region is 3.28 p.u., and the overvoltage level between the branch reactor is 3.83 p.u. The proposed arrester configuration can effectively suppress the overvoltage, and the energy absorbed by each arrester meets the requirements. The research results can provide a basis for the parameter design and insulation coordination of flexible low-frequency converter stations.