Railway electrification was initially adopted by the New Zealand Railways in New Zealand
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 2014–15. Electrification of long distance services on the North Island
Main Trunk (NIMT) dates from 1986, although KiwiRail is now considering diesel operation
of the NIMT. New long tunnels e.g. 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 1500 V DC, but the NIMT (1986) and Auckland suburban services (from
2014) use 25 kV AC; all with overhead catenary supply. The use of 16 kV AC (at 16.7 Hz) for
the NIMT was proposed in 1950.
== History ==
=== Stockton mine railway ===
The Stockton mine railway was, in 1908, New Zealand’s first electric railway. It carried
coal from the Westport-Stockton Coal Companies mine to the NZR railhead at Ngakawau on the
West Coast of the South Island from 1908 to 1953, when it was replaced by an aerial cableway.
The line was 10.5 km long, with 2.4 km in two long tunnels. The system used 275 V DC
from a low overhead line via trolley poles, and 915 mm gauge track. The seven locos were
of low built “mine” type.
=== Otira and Lyttelton Tunnels ===
The first NZR line to be electrified in New Zealand was the Otira Tunnel in 1923. This
long tunnel (8.55 km) with a steep gradient (1 in 33) could not have been worked by steam.
In 1916 there was consideration of electrification of the entire 100 km section with steep grades
from Jackson (West Coast) to Springfield (Canterbury), but in 1923 just the Otira-Arthur’s Pass
section (14 km) was electrified. In 1929 the Lyttelton Line through the Lyttelton Rail
Tunnel was electrified. This tunnel (opened in 1867) was short and had a lesser gradient
than Otira (0.3%) but replacement of steam operation was desirable.
=== The Merz & McLellan Report === The 1925 report by the English consulting
firm of Merz & McLellan was commissioned by the Minister of Railways Gordon Coates to
investigate electrification of suburban services in the four main centres of Auckland, Wellington,
Christchurch and Dunedin. For Christchurch it recommended electrification of the Lyttelton
Line but not the main lines north and south. Now only Auckland and Wellington have suburban
passenger services. The firm’s partner Charles Merz of Newcastle upon Tyne had reported on
Melbourne suburban electrification in 1908 and 1912.
=== Wellington electrification ===
Several Wellington lines were then electrified: in 1938, the Johnsonville Line; and from 1940
the Kapiti Line section of the NIMT north of Wellington to Paekakariki through the two
Tawa Tunnels which were part of the Tawa Flat Deviation. This line also had steep gradients
(1 in 57) on the bank from Paremata up to Pukerua Bay.
In February 1946 it was decided to electrify the remaining Wellington suburban lines to
the Hutt Valley as there was a shortage of coal for locomotives, and also to replace
commuter steam trains with EMUs, as the Hutt Valley was now largely residential with new
state housing replacing market gardens. When the extra EMUs arrived in 1949 they were initially
used for the Kapiti Line to Paekakariki while the Hutt Valley lines to Upper Hutt and Melling
were electrified. So in the Hutt Valley, EMUs were supplemented in peak periods by older
carriages hauled by electric locomotives until they were replaced by the Ganz-Mavag EMUs
from 1986.
The Johnsonville and Melling lines were short branch lines which were originally part of
the main line (NIMT) north and the Hutt Valley line to the Wairarapa, until the lines replaced
by deviations. The sections of these lines that were retained were mainly used for suburban
commuter services, with initially some stock traffic to Johnsonville (later to Raroa).
=== Dieselification === For two new long tunnels, diesel operation
was more economic than a short electrified section; the Rimutaka Tunnel (1955) and the
Kaimai Tunnel (1978). The Rimutaka Tunnel required an intermediate ventilation shaft.
From 1967 diesel locomotives (DA class) replaced electric locomotives (EW class) on freight
trains south of Paekakariki on the Kapiti Line after the track in some older tunnels
was lowered, so diesels could run under the catenary into Wellington.
On two existing electrified tunnels the electrified section was only a small part of the total
line. Hence the Lyttelton Rail Tunnel was operated by diesel locomotives from 19 September
1970. The Otira Tunnel was long and steep, so for dieselisation from 1997 a door and
special ventilation fans were fitted (electrification of the whole 100 km Springfield to Jackson
section with its steep gradients had been considered in 1916 and in the 1950s; possibly
using 50 Hz AC not DC).
=== Electrification of the NIMT ===
In 1950 electrification of the entire North Island Main Trunk (NIMT) from Auckland to
Paekakariki (the terminus of the Wellington electrification) was proposed by the General
Manager F. W. Aickin, with 16 kV AC (at 16.7 Hz) used for the 657 route miles or 1,000
km of track. The system would have been similar to that in Germany (also low-frequency but
at 15 kV AC). While the NIMT represented only 12% of the network length, it carried 40%
of the system tonnage (13% more than total South Island tonnage). A hundred Bo-Bo locomotives
would be required, and in Auckland there would be suburban electric services to Henderson
east of Auckland and to Papakura 34 km south of Auckland. A report by two Swedish engineers
(Thelander and Edenius) was also obtained. Their report said electrification was a matter
of necessity and estimated greater capital cost saving with AC electrification instead
of DC (1500 V or 3000 V) than Aickin had allowed for. But the proposal was dropped in favour
of dieselisation, with the first mainline DF class diesel locomotives arriving in 1954.
In 1974 a study was undertaken to consider the looming problem of "traffic saturation"
on the mountainous central section, particularly the Raurimu Spiral. In 1975 the study recommended
electrification using 25 kV AC, but with decline in traffic was dropped. But in the late 1970s
with the "oil shocks" of 1973 and 1979 the Third National Government embarked on several
projects to reduce dependence on imported oil.
Electrification of the 412-km centre section of the NIMT was one of the Think Big projects,
and probably the most successful of them. The project was approved in December 1981;
specifications were prepared in 1982 and tenders let in 1982–83. Other works improved the
line by easing curves and gradients and replacing signalling. Work started in late 1984 and
was completed in 1988—though on 24 June rather than March as planned—with a train
traversing the whole section. Brush Traction supplied 22 EF class locomotives; the design
was scaled up to the Eurotunnel Class 9 locomotives supplied by Brush for the Channel Tunnel.In
December 2016 KiwiRail announced that it proposed to dieselise this section of the NIMT due
to the age of the present electric locomotives and the cost and time delays in changing locomotives
at each end of the electrified section at Te Rapa and Palmerston North.
=== Electrification of the Auckland suburban network ===
The extensive suburban rail network around Auckland which had been operated by steam
and then by diesel was electrified using 25 kV AC between April 2014 and July 2015. Electrification
goes 34 km south to Papakura, and there are no immediate plans to extend further south
on the NIMT to Pukekohe or as far as Hamilton (the Waikato Connection and earlier Auckland-Hamilton
passenger services have not succeeded).
== Existing systems ==
=== Auckland metro === All electrified lines in the Auckland metro
area uses the 25 kV 50 Hz AC system. The system is fed from Transpower's 220 kV
grid at two locations: Penrose and Southdown
=== North Island Main Trunk ===
The North Island Main Trunk uses 25 kV 50 Hz AC. The system used is a 25-0-25 kV auto-transformer
system, with auto-transformers spaced along the line interconnecting the positive 25 kV
contact line and negative 25 kV feeder line. The system is fed at four traction substations,
taking power from Transpower's 220 kV national grid.
=== Wellington metro === All electrified lines in the Wellington metro
area use the 1500 V DC system.
Johnsonville Line: completed 2 June 1938. Kapiti Line: Wellington Station to Paekakariki
completed 1940; extended to Paraparaumu March 1983; extended to Waikanae 20 February 2011.
Hutt Valley Line: Wellington Distant Junction to Taita completed 14 September 1953; extended
to Upper Hutt 24 July 1955 Melling Line: Hutt Valley Junction to Lower
Hutt (Western Hutt) completed 23 September 1953; extended to Melling 1 March 1954.
The Wellington metro system is fed by 18 traction substations, taking power from Wellington
Electricity's (Welllington metro) or Electra's (Kapiti Coast) 11 kV distribution networks.
There are also a number of cross-tie substations, which do not feed electricity into the lines
but perform switching functions.
== Further reading == Churchman, Geoffrey B. (1995). Railway Electrification
in Australia and New Zealand. Sydney & Wellington: IPL Books. ISBN 0-908876-79-3.
Leitch, David; Stott, Bob (1988). New Zealand Railways: The First 125 years. Auckland: Heinemann
Reed. ISBN 0-7900-0000-8. Sinclair, Roy (1987). Rail: The Great New
Zealand Adventure. Wellington: Grantham House. pp. 86–91. ISBN 1-86934-013-2.
Pierre, Bill (1981). North Island Main Trunk: An Illustrated History. Auckland: Reed. ISBN
0-589-01316-5. Redward, Roger (1974). Railway Electrification
in New Zealand: An illustrated survey. Wellington: Southern Press.
Pickering, A J; Spicer, I D (ed) (1970). Pioneer Electrics: A survey of railway electrification
in the South Island:. Christchurch: Tramways Historical Society.CS1 maint: Extra text:
authors list (link