Figure 1

Schematic drawing of the 400-kV grid in mainland Spain and the surroundings. A number has been assigned to each substation according to alphabetical order, although after revisions, a second round of numbers were added after the 144th and non-Spanish ones were added (also alphabetically) at the end of the sequence. The nodes 156 and 132, which correspond to the Manzanares and Vandellòs substations, respectively, have been highlighted in blue, and data from nodes 156 and 132 will be referred to in Figures 2 and 3, and in Figure 11, respectively. The thicker lines indicate links with multiple lines.