Identification of key lines in complex power grid based on power flow entropy

In most cases, large scale blackouts are due to the successive malfunction of a large number of components often triggered by an initial disturbance or event, such as short circuits of transmission lines, protection device misoperation and bad weather. But analyses of these blackouts also show that not all the initial disturbances could lead to major cascading failures. The scale of a cascading failure could be influenced by the firstly tripped line which trips out firstly after the initial disturbance. For most of the lines in a complex power grid, when they act as the firstly tripped line, cascading failures stop quickly and could not proceed to a large scale. But for some lines, referred to as key lines in this paper, when they act as the firstly tripped line, cascading failures could cause many lines trip out progressively. In this paper, we propose a method for identification of key lines in complex power grid base on the new concept of power flow entropy.