The smart grid can be defined as a modern electric power grid infrastructure for improved efficiency, reliability and safety, with smooth integration of renewable and alternative energy sources, through automated control and modern communications technologies. The increased need for more effective control of power electrical systems, turned the development of smart grids the main object of study for many researchers. This paper proposes a digital system for condition monitoring, diagnosis and supervisory control applied to smart grids. The system is based on hybrid network architecture, consisting of a Wired Infrastructure, a Wireless Sensor Network (WSN) and a Power Line Communications (PLC). The system is based on three hardware topologies responsible for the signal acquisition, processing, and transmission: Remote Data Acquisition Units (RDAU's), Intelligent Sensors Modules (ISM's) and a PLC's Modem. The basic characteristics of the presented integrated system are: (a) easy and low cost implementation, (b) easy to set up by user, (c) easy implementation of redundant routines (security), (d) easy expandability, (e) portability/versatility, (f) extended network lifetime, and (g) open system.