On the basis of the top-level design principle and thought of system protection of wide-area interconnection power grids and combining with the large receiving-end grid characteristics of North China multi-ultra-high voltage(UHV)AC and DC strong coupling

the safety and stability characteristics under typical fault disturbance of UHV AC and DC in North China power grid are analyzed. Due to the inelasticity of prevention and control for safety and stability problems in the new network pattern

the fortification criterion and multi-measure prevention and control technology of system protection in North China are studied

and the functional configuration and implementation plan of system protection in North China are further proposed. Combined with the actual power grid of North China in the target year

the simulation verifies the validity of the main functions and key technologies of system protection in North China.