To meet the requirements of power system safe and economical operation under increasingly complicated conditions

a transient stability limit interval and correlation indices calculation method of the transmission sections is proposed. By comprehensively considering security and stability margin

pattern

component participation factors under the contingencies have been obtained based on the transient security and stability quantitative analysis method. And the transmission sections power sensitivity of different generator and load buses

the transmission limit influence factors of the generator and load buses are given. On this basis

the maximum and minimum transmission section power limit values are calculated by adjusting different generator and load power. Based on security and stability margin screening the key faults with transmission section have been obtained; the correlation indices of the transmission sections can be calculated using the comprehensive participation factors of the generators and the monitoring buses

which are calculated by the weighted average method with the margin as weights. The proposed method can provide technical means for operators to quickly grasp the transient security and stability level of different transmission sections and the degree of interaction between two transmission sections. The practicality and effectiveness of the proposed method are verified by a case in point of the power grid. This work is supported by State Grid Corporation of China and China Southern Power Grid Company Limited.