With the increase of power grid security indexes

the dispatcher’s ability to harness the grid is extremely limited. It is very necessary to use a comprehensive index to characterize the security states of the power grid. Thus

a method of power grid security index calculation and display based on the analytic hierarchy process (AHP) and variable weight mechanism is proposed. Based on several power grid security basic indexes

a calculating method considering dimension consistency

index structure rationality and electrical device differentiation

is proposed

and “1” of all the indexes is unified as the gap between safety and unsafety. The analytic hierarchy process and three mechanisms of weighting correction are used to determine index weights and aggregated into the comprehensive index. Besides

a method for dividing the operation security levels is presented and the display methods of power grid security index are also given. Numerical simulations are conducted in a certain power grid

the results showing that the proposed index of power system security is able to reflect the real-time statement of grid security and identify the fault with the system. Therefore

it is applicable to the modern dispatching system for watching power system security. This work is supported by State Grid Corporation of China and Beijing Natural Science Foundation (No. 3132035).