# Smart Grid Architecture for Rural Distribution Networks: Application to a Spanish Pilot Network
## 3 Electrical Actuations to Evolve the Rural Grid
### New Telecommunications Network
The whole set of communication links forms a meshed network, so networking technologies and services were deployed for successful operation of the PN. The TN according specific metric chooses the best path route from PN to control room, taking into account the existence and availability of previous communication infrastructures. Note that there are mainly two valid solutions to deploy these communications: the 2-layer solutions, which are based on Ethernet addresses; and the 3-layer solutions, which are based on Internet Protocol (IP) addresses. The SRG project focuses on the 3-layer solutions because of their advantages, which are an easier scalability, more cybersecurity, an easy integration with public telecommunications operator's networks, as well as with the International Electrotechnical Commission (IEC) protocol number 60870-5-104. This IEC protocol is an IP utilised for supervision, control and data acquisition in the power system applications [13; 52; 53]. An alternative to IEC-60870 is the IEC-61850 [53]. The IEC-61850 standard is a good solution that takes into account all aspects that are common in an electrical substation. It deals with general requirements, engineering, data models, communication solutions and compliance tests. A significant advantage of the IEC-61850 standard is its extensibility characteristic obtained by making the communication independent of the application by specifying a set of services and objects. This has allowed us to design different applications without depending on specific protocols. As a consequence, the data objects defined in the IEC-61850 standard allow us to apply them in multiple communication solutions without having to modify the models. However, despite the advantages of IEC-61850 over other standards in the project, we have opted for applying the IEC-60870, which focuses on the interaction between SCADA and RTUs. The reasons are diverse: (i) the previous experience at the time of executing the project; (ii) the complexity of deploying the IEC-61850 within the frame of the project; and (iii) the stringent requirements of this standard in terms of communications and related infrastructure. In more detail, the main logical transmission requirements are aspects related to: addressing, quality of service, topology discovery and routing, cybersecurity, network management and time synchronism. Addressing aspects are essential to clearly and uniquely identifying the origin and destination points. This is carried out through IP version 4 addresses that permit user identification. This solution, in comparison to a 2-layer one, is more scalable but also more complex. The requirements for applications in terms of bandwidth, latency and bit error rate are included within quality of service aspects. In particular, when different applications co-exist in the same network, or when certain users have more important information to transmit, it is very common to create different traffic flows and assign to each application a priority. In addition, 3-layer approaches segment the traffic through Virtual Private Networks (VPNs), and likewise 2-layer solutions with Virtual Local Area Networks. Topology discovery and routing aspects choose the best route to transmit the information. The solution adopted is based on one of the most common routing protocols, which is the Routing Information Protocol (RIP). RIP is a standardised distance vector protocol that uses the inherent capability of creating new routes when the original one is interrupted. The cybersecurity is a critical feature in the Smart Grid environments and is a broad subject that must be dealt with to form a number of different points of view. The messages to be transmitted must be ciphered to make sure that unauthorised recipients do not have access to the information, and the terminals themselves must have proper access passwords to make sure that their configuration is not changed and company policy must be enforced for personnel training.