## 2 Power Networks Nowadays  
Electric grids have moved a long way from their initial status to the current precise systems we have. Still, the evolution stopped somewhere in the 1960s and, thereafter, there has not been a significant change in the technologies employed or the backbone working mode. Smart grids focus precisely on this gap, trying to combine ICT with power networks, in order to bring the latter ones into the 21 st Century. The first step to this revolution was taken in the early 1990s when the UK Government privatised the electricity supply industry in England and Wales for the sake of competitiveness. This process was subsequently followed in many other countries. In most cases, the restructuring involves separating the electricity generation and retail from the natural monopoly functions of transport and distribution, breaking the old hierarchic vertical structure. The deregulation, in turn, leads to the establishment of a wholesale electricity market for electricity generation and a retail electricity market for electricity retailing. In any case, the underlying layout remained the same and there are basically two separate physical networks: the high-voltage (HV) ones (the higher the voltage, the less energy transformed into heat and, therefore, lost), which transmits the electricity nation-wide from the power station to the regional distribution networks, and the low-voltage (LV) ones, which deliver the electricity regionally to the client. Further, there are a number of elements that control the energy flow to make sure it is done in a safe way. Finally, at the bottom of the system, meters record the energy consumption of each client. Depending on the size and type of these customers, we may have different kinds of meters (e.g., residential in LV, industrial in LV or HV, _etc._) Currently, most of the LV meters worldwide have to be read _in situ_ (remote metering the most important function to be fulfilled in _smart metering_). In the upper layer, the Substation Data Concentrators (SDC) gather the load data from a number of meters (though sometimes, as in the USA, this component is replaced by direct access to the meters or access through a gateway). Then, the SDCs and, eventually, some meters, hang from the _Secondary Substation_ (SecST), which manages the energy deliverance in a certain zone. Further up, the _Primary Substation_ (PriST) receives HV energy and lowers it to the required distribution network voltage. Further, it is in charge of a number of SecSTs, SDCs, and, eventually, some industrial HV meters. Moreover, the protections, switches, and relays spread all over to prevent damages on the aforementioned elements and in the lines in case of failure or extreme conditions. Finally, in the uppermost level, human operators are in charge of managing current power network infrastructures. In this task, they are supported by diverse SCADA (Supervisory Control And Data Acquisition), EMS (energy management system), and DMS (demand-management system), conforming the so-called Central Controller Centre. As we may see, the architecture is framed in a very tight hierarchy. This picture has been blurred lately by the apparition of new technologies and models with mixed roles. First, distributed generation has broken the unique direction of the energy and now it may flow either way. Second, smart grids will enable data interchange from the client to the utility, and vice versa (e.g., to transmit a price signal), and between all the members of the systems, enabling customer-side active policies and new client-provider relationships (e.g., Demand-Side Management, a voluntary re-scheduling of customer's demand to smooth consumption peaks [17]). Third, _micro-grids_ and the EV, for instance, out-shape the classic rigidly-layered architecture by merging features of all the levels.