This paper addresses the issue of network partition used in power system analysis for ancillary services in distribution networks with distributed generation. Simplification and reduction of the computational effort in network calculation for centralized control can be achieved, through a definition of suitable partitioned clusters. The zoning problem is explored using a clustering process based on the k-means algorithm. The proposed method is implemented within a study case of voltage profile calculation in a 20 kV distribution network for steady state voltage control. The results show the performance of the method, with the caveat of the need of preliminary fitting of the parameters.Index Terms--Smart grid, distribution network, Clustering methods, dispersed storage and generation, power distribution, power system simulation.