1 The Smart Grid : A General Perspective

      1.1 Introduction

      The Smart Grid is a container of the most modern and evolutionary changes in the power system as a consequence of the advent and adoption of new technologies that progressively add new capabilities to the grid and help it to become a more efficient system. Indeed, the Smart Grid is neither a novel nor a static concept; however, it is bound to be disruptive from the perspective of the achievement of its objectives.

      The objectives of the Smart Grid have been broad and ambitious since its inception, decades ago. These objectives have been stimulated and become achievable due to the advances in electric grid technologies and the applicability of Information and Communication Technologies (ICTs) to the grid. With regard to the former, there are new technologies that can be added to the different segments of the grid and change the traditional electricity delivery model (e.g., Distributed Energy Resources [DER]). As per the latter, continuous ICTs' innovations have permeated all industries and the Society as a whole, paving the way toward a digital transformation in utilities, specifically in the areas close to the grid operation.

      The ambition of the Smart Grid is to integrate all these electric technologies and ICT innovations into a smart system, empowered with new applications and services, and able to operate more efficiently in all its aspects.

      This chapter elaborates on a comprehensive definition of what can be understood for a Smart Grid by introducing the basic elements of a power grid and enhancing those with telecommunication technologies. This definition is complemented with the main challenges that Smart Grids, and more specifically, telecommunication technologies applied to Smart Grids, must face in the coming years.

1.2 Electric Power Systems

Electricity is one of the cornerstones of our Society [1], and as such, its generation, transport, and distribution need to be a fully functional and efficient system. All the dependencies that other essential services for the functioning of the economy and society have on electricity (see Figure 1.1), and the extent to which electricity is also affected by all of them, determine the need to have all of these services evolving in an efficient and coordinated way, while stimulating the adoption of new technologies.

Figure 1.1 Electricity at the core of critical services. Dependencies are based on services provided among them.

      Source: Department of Energy – USA [1].

      It is widely recognized that electricity in general, and electrification in particular, are among the major achievements of the twentieth century [2], despite the fact that there are still big parts of the world where electricity is not affordable (electrification today is total in developed countries, while, as reported in [3], there were still 1100 million people in 2016 who live without electricity elsewhere). As A.C. Clarke expressed it in [2], “the harnessing and taming of electricity, first for communications and then for power, is the event that divides our age from all those that have gone before.” However, it is also true that electricity supply tends to go unnoticed, as a nearly invisible service attached to our modern way of life, that “is already there.”

      The electric grid is a complex system reaching every other activity. It is composed of a large number of elements, spread all over where human activity is present; it is controlled to deliver its service in the most reliable and resilient manner. From a purely technical perspective, the grid has evolved improving its associated control capabilities, from its center to the edge across the entire system, and inherits much of the means used in times where remote control was only a wish, and needed electromechanical elements and procedures to minimize manual interventions for incidents resolution. Moreover, and as an inherent characteristic of its nature, much of the electric system is regulated by Governments, meaning that the control over the grid goes beyond the network technical aspects.

      1.2.1 Electricity

      Electricity is the universal and standard way to transform energy and get it transported everywhere and to everyone. Electricity, as the object of the grid, exhibits a series of properties that justify the complexity of the system behind it.

The size and geographic extension of electric power systems are conditioned by their scope, as a consequence of the purpose of carrying the energy from the places where it is most conveniently produced to the places where it is needed. This is achieved by means of a network (the grid, i.e., Transmission and Distribution) of interconnected elements (e.g., generation systems, power lines, substations) spread over necessarily large geographical areas and integrated to work as a whole.

      Electricity, as a product, cannot in practice be stored or shipped in containers. Despite the technological advances in electric batteries and other storage apparatus, handling any amount of energy comparable to a representative percentage of the system's dimension is nowadays still far from feasible (performance aspects, and other limiting factors, may be solved in the future). Thus:

      From an operational perspective, deviations from normal operation may cause the instantaneous reconfiguration of power flows that may have substantial effects on facilities (e.g., substations, power lines, etc.) in the grid and propagate almost instantaneously across the entire system.

      Finally, electric power consumption is sensitive to the technical properties of the electricity supply, to the extent that devices may malfunction or simply cease to operate unless the voltage wave is stable over time within certain parameters including shape (sinusoidal), frequency (cycles per second), and value (voltage). The system must have mechanisms to react (detect and respond) instantly to unexpected situations and avoid degradations in service quality.

      1.2.1.1 Frequency and Voltage

      The frequency of the electricity signal in the different world regions is either