These countries have the longest transmission lines because they have a high demand for electricity in densely populated urban centers, which are often located far from major power generation sources. For example, China's UHVDC lines connect remote hydro, solar, and coal plants in its western regions to the industrial east. Similarly, Brazil's longest lines transport power from large hydroelectric dams in the Amazon to cities like Rio de Janeiro and São Paulo. The geographical distance between power generation and consumption centers necessitates the use of long-distance transmission lines.