Considering the low granularity of temporal physical malicious attacks on transmission system equipment

this paper proposes a structured identification method for critical equipment in transmission systems under the regional power outage. First

geographic clustering of facilities is utilized as the maximum granularity for malicious physical attack

leading to the development of a modular transmission system model. Second

this paper considers the characteristics of fault propagation among facilities and

in conjunction with equipment recoverability

constructs a bi-level optimization model to identify critical equipment that can cause sustained power failure in specific areas under the temporal malicious attack. Additionally

a decision variable selection method is introduced based on the search for regional power supply paths. It excludes facilities outside the regional power supply path from the decision set

significantly enhancing solution efficiency. The results of case study indicate that

compared to traditional line-attack strategies

when attackers implement modular attacks

they can continuously target equipment with longer recovery times

thereby compounding the effects of the attacks and maximizing the incapacitation of targeted regions in the shortest time possible. Furthermore

through appropriate parameter adjustments

additional losses outside the region can be kept within tolerable limits.