The classic N-k security analysis method often selects the source fault accident set with the objective of maximizing system impact

ignoring the synergistic amplification effect of cyber-physical interaction and the propagation process of cross-domain cascading failures

resulting in a tendency to be overly conservative. Therefore

the paper first characterizes the changes in system topology and operating states in the source of cyber-physical collaborative faults and cross-domain cascading failures propagation

revealing the impact mechanism of system observability and controllability on cross-domain fault propagation. Secondly

establish a bi-level optimization model for selecting N-k coordinated fault scenarios considering inter-domain cascading failures. The upper layer aims to maximize load loss and identify high-risk cyber-physical collaborative fault scenarios and cross-domain cascading failure propagation paths. The lower layer aims to minimize load loss and make optimal adjustments to controllable generators and loads. Then

a network flow algorithm is used to quickly solve the proposed model. Finally

simulation verifications are conducted on the IEEE 39 bus system and the 500 kV bus system in a Chinese province

and results verify that the proposed model can effectively identify high-risk high-order collaborative fault combinations and cross-domain cascading failure propagation paths in the system; When the scale of communication channel failures is small

controllability plays a dominant role in fault propagation

and priority should be given to increasing backup channels for control services. When the scale of communication channel failures is large

observability plays a dominant role in fault propagation

and priority should be given to increasing backup channels for measurement services.