# Telecommunication Technologies for Smart Grid Projects with Focus on Smart Metering Applications
## 1 Introduction  
The current power grid needs to constantly evolve to adapt to the increasing technological demands. Particularly, the development and growth of Renewable Energy Sources (RES) has implied a transformation in the way the energy is produced and stored. In addition, the need to reduce the total CO\({}_{2}\) emissions calls for a better and more efficient energy usage. Modern power grids are adapting to cope with this new scenario, evolving to accommodate the integration of renewable energy sources and to enable a more efficient energy management through automated control and modern telecommunication technologies [1]. A smart grid implies that a vast amount of information will need to be handled. The integration of renewable energy sources requires a constant monitoring and control of the power grid. As a consequence, the operation of the whole grid requires an efficient management of energy generation, transmission and distribution. For this reason, the role of the telecommunication technologies used in the smart grid is of vital importance. In general, there are three main domains of applications for the smart grid network: the High Voltage (HV) network used for the electricity transmission, the Medium Voltage (MV) network used for the electricity distribution and the Low Voltage (LV) network used to provide electricity at end-users [2]. Specifically for the LV network, special attention is given to neighborhood and building area networks. In [3] the technological solutions for this type of networks are listed. Smart metering is an important part of the LV network, because it contributes in transmitting energy consumption/generation data towards the utilities andinformation data towards the smart meters. Therefore, they play a key role in energy management and saving. There are several telecommunication technologies utilised by smart metering applications and they are mainly distinguished according to the transmission medium used for the signals, thus being divided into wired and wireless. A popular wired technology is Power Line Communications (PLC), which refers to the use of the existing power lines for the signal transmission. A benefit of this technology is that there is no need for new infrastructure. PLC technologies can be classified into two categories: Broadband PLC (BB-PLC) and Narrowband PLC (NB-PLC) [4]. Many wireless techniques can be used depending on the type of signal transmission examined, like the ZigBee or cellular wireless technologies. In general, there are two links for transmitting data from the smart meter to the control center: the first link carries data from the smart meter to a data concentrator whereas the second link connects this data concentrator to the data center [5]. In the rest of the paper, we refer to these links for smart meter data communication as \"first\" and \"second\" link. Figure 1 shows this concept of smart meters communication to the utility center through data concentrators. In Figure 1, it is shown that various technological solutions can be used for both links. In this paper, we aim at identifying the telecommunication technologies selected in reality for smart grids with emphasis on smart metering applications. For this purpose, a survey is performed based on the smart grid projects realised in Europe, as presented in [6], and the technological solutions applied in them. In general there are/have been more than 450 smart grid projects examining different issues; however, we select the projects directly or indirectly involving LV smart metering applications and special focus is given to the telecommunication technologies selected for them. The scope is to give a clear picture of the trends in the field and to provide readers with valuable information about what has been used in practice. To complete the picture, we present the technological solutions chosen by several European countries with respect to their national smart meter roll-out.