Railway electrification in New Zealand

Railway electrification in New Zealand consists of three separate electric systems, all on the North Island. Electrification was initially adopted by the New Zealand Railways for long tunnels; the Otira Tunnel, the Lyttelton Rail Tunnel and the two Tawa Tunnels of the Tawa Flat Deviation. Electrification of Wellington suburban services started with the Johnsonville Line and Kapiti Line out of Wellington from the 1930s. Auckland suburban services were electrified in 2014–2015. Electrification of long-distance services on the North Island Main Trunk (NIMT) dates from 1986. New long tunnels, for example the Rimutaka Tunnel and the Kaimai Tunnel, were operated by diesels, and the Otira and Lyttelton Tunnels have converted to diesel operation.

From 1908 to 1953, there was an electrified mine railway from the Stockton mine on the West Coast of the South Island.

Earlier NZR electrified routes from 1923 to the 1940s operated at 1,500 V DC, but the NIMT (1986) and Auckland suburban services (from 2014) use 25 kV 50 Hz AC; all with overhead catenary supply. The use of 16 kV 16.7 Hz AC for the NIMT was proposed in 1950.