The Innovative Three-Phase Railway Electrification of the Simplon Tunnel

The Simplon railway tunnel, connecting Italy with Switzerland though the Alps, opened in 1906. For over 70 years it has been the longest tunnel in the world. The paper describes the innovative three-phase system adopted for the railway electrification, following the first experiment of the Italian Valtellina line (1902). The electric line was built by the Swiss company Brown Boveri, while the first locomotives were produced by the Hungarian company Ganz.