Three-phase AC railway electrification
Three-phase AC railway electrification, which promised some advantages over established DC electric rail power and steam traction, started at the turn of the twentieth century. The first standard gauge line, from 1899 to 1933, was from Burgdorf to Thun in Switzerland (40 km or 25 mi).
Source: Wikipedia — Three-phase AC railway electrification (CC BY-SA 4.0)