This paper presents a transient energy based screening approach for quickly identifying potential critical attacks that might have significant impacts on power system transient stability. Specifically

the proposed approach focuses on the total transient energy injected into power systems as the result of assumptive cyber attacks. The computational improvements of the proposed method are significant as the time-domain simulations can be avoided. The efficacy of the proposed approach is demonstrated using a practical power system with various cyber attack scenarios. The identification results of the proposed method can be used to guide more detailed impact analysis and to develop more effective countermeasures against cyber attacks.