I. Introduction
Under the new electricity reform policy, the transmission and distribution price has challenged the grid company to continuously improve the management level and reduce the operation and maintenance costs [1] . Carrying out the life cycle economic benefit evaluation of power grid projects is the key to speeding up the transformation and upgrading of power grids and improving investment efficiency. At present, the operation and maintenance costs of a single grid project cannot be accounted accurately. So the project operation and maintenance costs is usually measured by the proportion of fixed assets and total operation and maintenance costs when we do the economic evaluation of the grid project [2 – 3 ] . However, this costs sharing method only considers the importance of grid assets, and ignores the impact of grid engineering scale, operation and maintenance environment, and grid security on operation and maintenance workload. So, it cannot truly and objectively reflect the actual operation and maintenance costs. The unreasonable allocation of power grid operation and maintenance costs directly affects the quality of power grid operation and maintenance management, which brings hidden dangers to the safe and stable operation of the power grid.