For achieving the online calculation of the theoretical line loss for the whole network

in this paper a kind of parallel calculation method of line loss for large-scale power grid is proposed on the basis of the existed decomposition coordination calculation model.The method uses the improved Fast-Newman algorithm for network division

reduces the influence of boundary coordinationand realizes the selection of line loss calculation methods for different types of networks.Then

a double-layer iterative algorithm is introduced by the use of equivalent value of the outer buffer network so to achieve the uniform convergence of the state quantity of the sub-net boundary through the outer iteration of the boundary vector.The Matlab parallel toolbox is used for verification on IEEE 39 node system and the actual regional power grid.It is shown by the result that the proposed method has good computational accuracy and acceleration effect and is suitable for online computing systems.