## 1 Introduction
However, it neglects the impact of system transient dynamics on the fault sequence, making it difficult to capture chain reactions triggered by equipment transients and protection actions at short time scales [16]. On the other hand, the cascading failure model based on DC power flow (DF-CFS) is widely applied in large-scale grid analysis due to its computational efficiency. However, it overlooks crucial factors such as voltage stability and angle dynamics [17]. By integrating extreme weather factors with methods for quantifying abnormal equipment states, we can establish both equipment anomalies and hypothetical scenarios for the power grid. Combining the risk index values from power flow analysis under specific scenarios with accident probabilities allows for quantifying the overall operational risk of the system [18]. A specific type of hypothetical scenario is the fault chain, where an initial disturbance leads to multiple interrelated cascading equipment failures [19]. Reference [20] examined the impact of extreme high temperatures on load and transmission line capacity, and developed an fault chain model that accounts for fault sequences. Fault chains have a broad impact and are highly destructive. Consequently, researchers are focusing on strategies to suppress the propagation of these chains or mitigate their risks during system planning and operation [21]. As tropical cyclones pass, the extreme meteorological factors affecting power grid equipment and the equipment's abnormal states evolve continuously. Traditional fault chains, which previously considered only overloads and power flow risk factors, have evolved to account for the coupling of time-varying extreme weather conditions and power flow risks [22]. To address this, we propose a risk assessment method that incorporates the spatiotemporal evolution of grid anomalies during tropical cyclones. First, the impact mechanisms of tropical cyclones on grid equipment, including transmission lines and wind power, are analyzed to identify the time-varying abnormal states of grid equipment during cyclone events. Second, the evolution patterns of system anomalies under the coupling and interaction of time-varying extreme weather factors and power flow risks are examined. Third, alternating simulations of equipment failures induced by extreme weather and power flow redistributions are conducted based on the coupling mechanism, leading to the development of methods for constructing fault chains and scenario sets during tropical cyclones. Finally, the overall system risk assessment results are presented, incorporating uncertainties in extreme weather factors and grid parameters associated with tropical cyclones. The main contributions of the paper include the following:  
* Incorporating the spatiotemporal trajectory of typhoons, this study examined the time-varying abnormal states of source-grid equipment under typhoon impacts, revealing the spatiotemporal characteristics of grid faults. Based on these characteristics, the study further analyzed the spatiotemporal evolution mechanism of grid anomalies caused by the coupling of extreme weather factors and power flow, identifying the propagation paths of grid anomalies. * This study utilizes a risk assessment method that considers the spatiotemporal evolution of grid anomalies. This method captures the time-varying states of grid components under extreme weather and power flow interactions. It models cascading failures, constructs fault chains, and calculates risk indicators, providing accurate risk quantification and guidance for disaster prevention. Risk Assessment Research Framework Considering the Spatiotemporal Evolution of Power Grid Anomalies Under Tropical Cyclones  
The core goal of this study is to deeply analyze the fault evolution process of the power grid system under the influence of extreme weather such as typhoons by combining extreme meteorological factors with the dynamic changes in power grid flow.