With the decrease in the total electricity consumption growth rate

how to improve the efficiency of the transmission network without violating the safety constraints has become an important concern in the planning and operation of power grid. For this reason

an evaluation method for transmission grid efficiency considering the accident probability

based on the No. 599 order issued by the State Council

is proposed. This method calculates the accident probability using the cascading failure model

which takes the actual power system characteristics into account to guide the planning and operation of power grid. Meanwhile

it has avoided the defect that actual statistical data gathered from grids with different features cannot be used for horizontal comparison directly. A regional power grid in Hubei Province is selected to verify the effectiveness of the evaluation method

and the factors affecting the efficiency increment of the transmission network are discussed.