An identification of the key branch for large-scale power transmission line is the key to deal with the interlocking fault and the whole network breakdown fault quickly.For this reason

a kind of comprehensive identification method of the key transmission lines of power grid based on power transmission distribution factor and branch transient stability function is proposed.Firstly

from the point of view of power network structure

the power transmission distribution factor function is used to quantify the key events of each branch in transmission power network.Secondly

from the point of view of dynamic operation of power network

the transient stability function of the branch is adopted to solve the transient potential energy stability of each branch with purpose of evaluating the fragility of each branch of power network.Finally

the two evaluation methods are combined to construct the critical comprehensive evaluation function of power grid lines so to scientifically quantify the role of each transmission line in the whole power transmission network.The effectiveness of the comprehensive evaluation method is simulated and verified in the IEEE 39 node system.