The evolution of the topology of high-voltage electricity networks

The electricity network represents an example of an evolving complex system. The first local networks contained only a few nodes, but within several decades, they have evolved into a highly connected continental system. The growth of these networks was influenced by various factors such as economic, demographic, political and technological developments. In this paper, we analyse the growth of the French 400 kV electricity transmission network from its establishment in 1960 until the year 2000. We study the different topological characteristics that describe the intensity of the growth process, such as the number of nodes, the number of lines, the average node connectivity and the overall length of wires. We compare these results with several economic and demographic indicators in order to identify the factors which correlate with the growth rate of the electricity network. Apart from this, we evaluate how the topological efficiency and vulnerability measures (clustering coefficient, information centrality, betweenness centrality) evolve in the course of time. The decisions regarding the power grid topology are influenced by many, very often contradictory factors, such as costs, the size of the covered area, demand, fault tolerance, reliability and quality of service. Our results yield a deeper insight into the process of Critical Infrastructure (CI) construction. The evolution of the topology of high-voltage electricity networks 73