Power Grid: High-Voltage DC Transmission Passage C was first released as day 24 of the Brettspiel Adventskalender 2015, and this mini-expansion is playable solely with the Power Grid map of Germany. It was later available in a pack of promos for backing Game Boy Geek 2017 Kickstarter
In future years, Germany plans a new high-voltage transmission line from North Germany to South Germany to deliver the electricity produced by wind power to the regions in South Germany with demand for that power. You are collectively building this transmission line, so step by step your power companies will not need to pay connection costs anymore between Cuxhaven and Stuttgart. Sadly, the construction of this transmission line is paid with tax money, so you must pay taxes to supply these cities with electricity.