Transmission contribution degree index and its application in critical line and node identification in the power system is proposed. The method based on the maximum flow and the complex network theory

overcome the limitation that power flow is supposed to be transferred along the shortest path when compared with the present research

take all the possible transmission path among different “source-load” pair into consideration. At the same time the directed and weighted topological model of power gird which based on the flow direction is proposed

and define the power transfer ability of line as the constraint

the physical background is more suitable for the actual of power system. The line transmission contribution degree index synthesize the depth and breadth that line is utilized

the node transmission contribution degree index reflect the ability to undertake and transfer the flow. The test on IEEE-39 power system demonstrates the validity when compared with the present methods.