Short-term multiple fault risk assessment for power systems considering unexpected actions of protection system under weather disasters

• Coupled fault probability model of primary and secondary equipment under weather disasters. • System risk expansion modes caused by false and failure actions of protection system. • Operational risk of branch power flow overlimit, but voltage overlimit, and system load loss. • Screen weak links of the power system and the fault propagation process in the high-risk scenario. The occurrence of weather disasters expands the multiple fault risk of the new power system with a high proportion of renewable energy sources. The unexpected actions of the protection system will further promote the propagation of multiple fault risks. Therefore, a short-term multiple fault risk assessment method for power systems considering unexpected actions of the protection system under weather disasters is proposed in this paper. First, the modes of risk expansion caused by unexpected actions of the protection system is analyzed. Second, a coupled fault probability model of primary and secondary equipment under weather disasters is established, which comprehensively considers the system risk expansion modes caused by false and failure actions of protection system for power grids and grid-related protection for renewable energy sources. Then, the risk indexes such as branch power flow overlimit, bus voltage overlimit, and load loss of power systems are calculated; the weak links and high-risk accident chains are screened. Finally, the effectiveness of the proposed method is demonstrated on a modified IEEE 39-bus power system by comparing four simulation scenarios. The results verify that the proposed method can more accurately reflect the interaction between primary and secondary equipment after the occurrence of a fault, and reveal the propagation process of multiple faults in the power system. It can provide decision-making support for risk prevention and weak link management for power system operators.