The paper analyzed the potential safety and stability control risk of the southwest power grid, presented the general online identification framework for operational risks of the second and third defense line of UHVDC sending-end power grid, elaborated the key techniques for realizing the aforementioned functions, including security control strategy/system protection strategy modelling, high frequency cutting generator strategy modelling , conflict detection for the control measures of the second and third defense line, practicability assessment method for security control strategy/system protection strategy, practicability assessment method of high frequency cutting generator strategy and other technologies. According to the actual application conditions of the southwest power grid, the system may provide dispatching users with more comprehensive Online identification for the operational risks the second and third defense line as well as discover the potential safety hazards and risks during operation of the power grid.