## 4 Communication Technologies for WSANs Applied to the SG
### The Origins of Communication Technologies in Electrical Grids  
The interest on the application of communication technologies in order to help the management tasks of electrical grids begins with the expansion of the electrical network and the increase of the number of connections and branched devices. The first objective at the beginning was to ensure the correct operation of the grid and to rapidly face possible disturbances and breakdowns [56]. In the 1950s analog communications were usually employed to measure the energy generation of power plants and the total consumption, as well as to control the frequency and the voltage of the grid. The development of digital computers from 1960 allowed the creation of Remote Terminal Units (RTUs), employed to obtain in real time the values of real and reactive powers as well as the state of the transmission electrical substations. The acquired values were sent to a central computer known as Master Terminal Unit (MTU), through dedicated communication channels: the Supervisory Control And Data Acquisition (SCADA) system was born [57; 58].  
The SCADA system was the best solution to be applied in the first electrical grids, whose structure was centralized. However, the energy market liberalization in the 1990s caused a decentralization of the grid and, therefore, the need for a revision of control methods. Nowadays, new communication technologies based on the Internet or on Common Information Model (CIM) are integrated in the traditional SCADA system, as can be seen in Figure 5.  
Moreover, the generalization of renewable sources, as well as the distributed generation and MGs expansion, is inducing a transformation of the distribution electrical grid [59; 60] that must evolve from a passive to an active role from the point of view of automation and management [61; 62]. The application of advanced management systems in electrical grids is the basis to transform them into Smart Grids. Some authors define as the \"Third Industrial Revolution\" the transformation of conventional electrical grids into SGs that include a large volume of renewable and distributed generation, managed by means of control systems based on communication protocols [63].  
Figure 5: Architecture of a modern Supervisory Control And Data Acquisition (SCADA) system, connected to Internet.  
This last aspect is essential because it reveals the need of a suitable communication network in order to monitor and transmit measured data from different parts of the electrical grid, allowing the detection of any operation problem and assuring a correct management of SGs and MGs [64]. The combination of communication techniques to collect and transmit measured data, and the grid management performed by means of those data is the basis of Automatic Meter Reading (AMR) systems [65]. Some interesting applications of AMR are the DR (real time pricing) [66; 67], fault and islanding detection [68], system protection, fraud detection and remote telemetry, among others. In this context, electrical MGs, due to the intelligent control and communication solutions that must be applied in order to monitor and manage their correct operation, can be considered a promising starting point to transform the conventional grid into a SG.