GridKit: European and North-American extracts

These files contain network models of the European and North-American high-voltage power grid, extracted by GridKit (https://github.com/bdw/GridKit).  These extracts form a topological network with stations in one file (vertices.csv) and lines in another (links.csv). This network is intended for use in power system analysis. OpenStreetMap is the primary data source for these networks.