To address cascading failure in power systems caused by secondary system failure in smart substations and to improve early warning accuracy, a cascading failure situation awareness method for smart substation operation and maintenance is studied. Based on protection principles and configurations, various modes of cascading failure caused by secondary system failure are analyzed, and the event chain templates of cascading failure path are constructed. Using the substation’s main wiring, instance-specific cascading failure path event chain sets are created for each primary device based on the templates. When a primary device fails, the system collects online alarm signals from its corresponding protection and adjacent protections to detect protection malfunctions or misoperations. These are matched with relevant events and conditions in the associated cascading failure path templates for that device, forming a set of pre-warning cascading failure paths to assess and forecast power outage consequences. This enables the identification of cascading failure risk points and provides early warnings to support operation and maintenance personnel. Case studies verify that the proposed method can effectively provide cascading failure warning for substation operation and operation and help prevent potential cascading failure.