This document discusses communications network requirements for substation automation. It describes how utilities are adopting IP and Ethernet-based intelligent electronic devices (IEDs) to improve grid performance and efficiency. This requires new communications network infrastructures within substations and between substations and control centers to handle increased traffic. The document outlines architectures that segment intra-substation and wide area network communications according to standards like IEC 61850. It also provides an example case study of a smart substation project in France where Nokia is implementing digital substations for grid improvements.