Abstract: The operation mode fast switching and change need to monitor AC tie line status in voltage source converter high-voltage direct-current (VSC-HVDC) power transmission system during the AC/DC parallel operation mode, In order to solve the problem of getting electric parameters by station control system. This paper proposes a scheme applying operational and monitoring device to get electric parameters, This paper analyses the discrimination strategy of operational and monitoring device and gives implementation plan to project, this paper can provide reference to project design.