Electrification of the Natal Main Line

Natal Main Line electrification
An electrically hauled passenger train
An electrically hauled express train in Natal, illustrated in 1928
Overview
LocaleSouth Africa
Termini
Service
TypeRailway electrification programme
SystemNatal Main Line
Operator(s)South African Railways and Harbours (original scheme)
Transnet Freight Rail (current freight services)
History
First electric services1925
Electric working to DurbanDecember 1936
Electric working to Volksrust1937
Technical
Line length526 kilometres (327 mi) (1937)
Track gauge1,067 mm (3 ft 6 in)
Electrification3 kV DC, overhead lines
Route (selected locations)

 Volksrust
Newcastle
Glencoe
Ladysmith
Colenso
Pietermaritzburg
Cato Ridge
Durban
North to south; not to scale. The initial scheme covered Glencoe–Pietermaritzburg. Branches and intermediate stations are omitted.

Electrification of the Natal Main Line was a programme undertaken by the South African Railways and Harbours (SAR&H) during the 1920s and 1930s to introduce electric traction on the 526-kilometre (327 mi) railway between Durban and Volksrust. Electric services began in Natal in 1925, the first main-line electric working on the South African Railways. The electrified route reached Durban in 1936 and Volksrust in 1937.

The initial scheme covered the mountainous route between Glencoe and Pietermaritzburg, where electrification offered a means of increasing coal-carrying capacity without immediately doubling the track. Electricity came from Colenso Power Station and was converted at automatic substations to 3 kV direct current (DC) for the locomotives. Electric working allowed heavier trains and shorter journey times, but rising cost estimates prompted parliamentary scrutiny of the initial scheme. Subsequent extensions used cheaper supporting structures and shared transmission infrastructure to reduce construction costs.

The project formed part of the development of South Africa's state electricity industry. Wartime delays affected expansion of the power supply, and equipment used exclusively for traction returned to railway ownership in 1948. Connection to the national grid in the 1970s was followed by the closure of Congella in 1978 and Colenso in 1985. The route subsequently became part of the freight corridor between Durban and Gauteng, retaining its 3 kV DC electrification.

Background and planning

The South African Railways and Harbours (SAR&H) carried coal from Natal to markets in Durban and the Transvaal over a route with steep gradients. Steam locomotives had to climb these gradients while carrying their own fuel. Electric traction offered greater power on climbs, reduced the need to transport locomotive coal and allowed energy to be recovered during descents. Southbound trains descended from Glencoe towards Colenso before climbing again through Estcourt to the uplands around Mooi River. The Estcourt–Mooi River section had a ruling gradient of 1 in 65, and the sharpest curves between Glencoe and Pietermaritzburg had a radius of 91 metres (300 ft).

SAR&H general manager William Hoy favoured electrification over doubling the Natal main line. The First World War interrupted his plans in 1914, but in 1917 he appointed Merz & McLellan to investigate electric working. Their report followed in June 1919. Although the consultants proposed starting at Durban, SAR&H gave priority to the mainly single-track Glencoe–Pietermaritzburg section. Growing coal traffic had brought the northern section close to the capacity of steam operation. Construction of the power station at Colenso began in September 1922.

With the support of Jan Smuts, Hoy intended electrification to stimulate industrial development beyond the railway itself. The consultants' investigations contributed both to the railway programme and to the establishment of the Electricity Supply Commission (Escom) in 1923, following the Electricity Act of 1922. SAR&H's concern about the cost and reliability of private or municipal electricity supplies favoured state provision, while large generating stations serving railways, towns and industry offered economies of scale.

Overseas experience informed the planning. In 1917, John Kirkland described the electrification of the Chicago, Milwaukee and St Paul Railway to South African engineers. Frederick William Mills, SAR&H's chief electrical engineer, accompanied Charles Merz over the proposed South African routes in 1919 and visited major railway electrification schemes in America and Europe in 1920–1921.

Electrical system and power supply

Power station with cooling towers, transformers and coal conveyors
Colenso Power Station viewed from the railway bridge over the Tugela River in 1971

The 1,067 mm (3 ft 6.0 in)-gauge railway adopted a 3 kV direct current (DC) system with overhead lines. The high power required by heavy trains on the mainly single-track route influenced the choice of voltage. Twelve automatic substations, spaced about 24 kilometres (15 mi) apart, supplied the line; their relatively close spacing reflected traffic density and the required operating speeds.

Colenso generated three-phase alternating current (AC) at 6.6 kV, which was stepped up to 88 kV for transmission. At each substation, transformers reduced the voltage and motor–generator sets converted the supply to DC. Each standard set was rated at 2 MW and used an AC motor to drive two 1.5 kV generators connected in series, providing the 3 kV required by the locomotives. The substations contained between one and three sets and operated automatically, starting and stopping their machinery without resident attendants.

SAR&H built Colenso Power Station beside the Tugela River, with access to both cooling water and the Glencoe coalfields. Escom, later renamed Eskom, took over the station and its transmission and distribution system in January 1927. The station then had a generating capacity of 60 MW. Traction dominated its early sales, and rapid changes in railway demand could overwhelm the generating plant; additional boilers helped it accommodate these fluctuations.

The power system also supplied towns along the railway. Pietermaritzburg began receiving Escom power on 17 June 1927. This contributed to the construction of five municipal substations and the city's conversion from direct to alternating current. Congella Power Station in Durban, opened in 1928, was intended to serve both municipal demand and future railway electrification. The railway extension to Durban initially continued to draw its power from Colenso.

Initial operation and performance

Three electric locomotives coupled together at the head of a freight train
Three Class 1E locomotives hauling a freight train, c. 1930

Test running took place between Ladysmith and Chieveley in October 1924. Commercial services began in 1925, initially between Ladysmith and Estcourt. Eskom's historical account records the official opening of the Glencoe–Pietermaritzburg electrification in June 1926.

The first locomotives were the Class 1E, four-axle units developing 1,200 horsepower (890 kW) each. They worked in groups of up to three under the control of one driver. Regenerative braking returned electricity to the supply on descents and allowed higher downhill speeds while keeping the conventional brakes in reserve.

Early operation was affected by lightning, damage from electrolysis in mast foundations, and wear on contact wires and pantographs. High-speed circuit breakers were used to interrupt arcs caused by lightning flashovers and protect the equipment.

By 1935, three electric locomotives could haul a 1,500-ton train between Glencoe and Pietermaritzburg in 10¼ hours, compared with a steam schedule of 16½ hours for smaller loads. Railway Wonders of the World estimated that electrification had increased the line's capacity by 60 per cent.

Costs and administration

Historian Renfrew Christie puts expenditure on the Glencoe–Pietermaritzburg scheme between 1923 and 1925 at just under £5 million, approximately equal to the value of machinery, plant and tools in Natal's private industries outside mining. Rising estimates prompted parliamentary scrutiny. In July 1925, Patrick Duncan questioned two increases totalling £1 million over an authorised estimate of £3,318,000, excluding locomotives. The Minister of Railways and Harbours acknowledged the increase but argued that the scheme needed time to demonstrate its results. The use of overseas consultants also attracted criticism. In a parliamentary debate in March 1927, Major Richards argued that railway engineers had proposed cheaper mast foundations and the reuse of old rails as masts.

Later extensions reduced construction costs through discarded rails, redesigned mast foundations and electric welding. Supporting both overhead traction equipment and 88 kV transmission lines on the same structures avoided the expense of a separate transmission route. In a 1936 discussion, Durban engineer John Roberts credited Douglas Herbert Leibbrandt, SAR&H's consulting engineer, with making extensions more affordable, while acknowledging criticism that the cheaper construction offered less protection against breakdown.

Extensions to Durban and Volksrust

The southern extension followed the newer route between Pietermaritzburg and Durban, with gradients of 1 in 66 rather than the older route's 1 in 33. Work between Cato Ridge and Durban included laying a second track through ten tunnels. Electrification from Pietermaritzburg to Cato Ridge took place between 1929 and 1931, and electric working reached Durban in December 1936.

To the north, electrification accompanied realignment of the line from Glencoe towards Volksrust. A restricted electric service began on 3 October 1937, before all the associated track works were finished. Steam locomotives initially assisted trains over the unfinished section between Ingogo and Laing's Nek Tunnel. The Durban–Johannesburg mail train was first hauled electrically throughout from Durban to Volksrust on 10 December 1937; the remaining deviation opened on 14 August 1938.

Subsequent development

The Second World War delayed expansion of the regional power supply. Generating equipment intended for Congella was requisitioned for Britain's Earley power station, and a replacement set was lost at sea through enemy action in 1943. Congella's new generating plant began operating in 1946, and the station started supplying railway traction in 1948. In April 1948, transmission lines and rectification equipment used exclusively for traction were transferred from Escom back to SAR&H.

Post-war modernisation combined new locomotives with improvements to the track. Classes 5E, 5E1 and 6E1 succeeded the early electric units, while double-tracking was completed between Glencoe and Newcastle in 1962 and between Danskraal and Uithoek in 1964. Reconstruction of the main line between Durban and Vooruitsig was completed in November 1984.

The regional electricity system was connected to the national 400 kV network in 1971–1972, allowing the older Natal power stations to reduce their output. Congella closed in December 1978; Colenso was decommissioned in September 1985.

By September 2026, the route formed part of the Container Corridor linking Durban's port with Gauteng, with freight services operated by Transnet Freight Rail. Transnet's network statement recorded continued use of 3 kV DC electrification and centralised train control, with colour-light signals, track circuits and axle counters. It also recorded reduced capacity caused by theft and vandalism of electrical and signalling equipment: missing overhead wires had required diesel operation on affected sections, including in the Ladysmith area, while signalling failures required manual authorisation of train movements.

See also

Notes

  1. ↑ Accounts differ on the introduction of full electric working. Soul of A Railway Part 12, quoting Campbell, gives June 1926 for Glencoe Junction–Masons Mill; Part 13 gives 27 July 1927 for Ladysmith–Glencoe. Leibbrandt and Owens give 1928 for full operation of Pietermaritzburg–Glencoe.

References

Citations

  1. 1 2 3 South African Railways and Harbours (1947). The South African Railways: History, Scope and Organisation. Johannesburg: South African Railways. p. 91. OCLC 5914900.
  2. 1 2 3 4 5 6 7 8 "Congella Power Station". Eskom Heritage. Archived from the original on 13 November 2026. Retrieved 13 November 2026.
  3. 1 2 3 4 5 "Our History". Transnet Freight Rail. Archived from the original on 14 February 2026. Retrieved 13 November 2026.
  4. 1 2 3 4 Pivnic, Les; Martin, Bruno. "Part 12: The Natal Main Line – north of Pietermaritzburg to Ladysmith". Soul of A Railway. Archived from the original on 20 January 2026. Retrieved 13 November 2026.
  5. 1 2 3 4 5 6 Pivnic, Les; Martin, Bruno. "Part 13: The Natal Main Line – from north of Ladysmith to Charlestown". Soul of A Railway. Archived from the original on 7 October 2026. Retrieved 13 November 2026.
  6. 1 2 3 4 5 6 7 8 "Colenso Power Station". Eskom Heritage. Archived from the original on 4 September 2026. Retrieved 13 November 2026.
  7. 1 2 3 Christie 1978, pp. 99–100.
  8. 1 2 Brazil, Henry (1928). Electrical Substations. London: Edward Arnold & Co. pp. 110–112.
  9. 1 2 3 4 5 "South African Electrification". Railway Wonders of the World. No. 48. 27 December 1935. pp. 1529–1532. Archived from the original on 14 May 2026.
  10. 1 2 "House of Assembly debates". ZA Hansards. 17 July 1925. Archived from the original on 13 November 2026. Retrieved 13 November 2026.
  11. 1 2 3 Penney, N. D. (1937). "Progress and Development in the Natal Central Undertaking of the Electricity Supply Commission. With Special Reference to the Past Ten Years". Proceedings of the Fifteenth Convention (PDF). Association of Municipal Electricity Undertakings of South Africa and Rhodesia. pp. 112–113, 125–126. Archived from the original (PDF) on 24 October 2023.
  12. 1 2 3 Christie, Renfrew (1984). "Coal, Railways and Escom, 1914–33". Electricity, Industry and Class in South Africa. London: Palgrave Macmillan. pp. 75–76. doi:10.1007/978-1-349-07030-5_5. ISBN 9781349070329.
  13. 1 2 Transnet Network Statement (Report) (Version 4 ed.). Transnet Rail Infrastructure Manager. September 2026. pp. 93–99, 101–102. Archived from the original on 21 September 2026. Retrieved 13 November 2026.
  14. ↑ AMEU 1936, pp. 148–149.
  15. 1 2 "Research Items" (PDF). Nature. 121 (3053): 726–728. 5 May 1928. doi:10.1038/121726a0. Archived (PDF) from the original on 13 November 2026.
  16. ↑ Whelan, Debbie (November 2014). "A very ordinary power: The evolution of the electrical substation in Pietermaritzburg, 1900–1960". New Contree (70): 157–158. Archived from the original on 13 November 2026.
  17. 1 2 AMEU 1936, p. 110.
  18. ↑ Christie 1978, p. 109.
  19. ↑ "House of Assembly debates: Railways and Harbours Appropriation (Part) Bill". ZA Hansards. 7 March 1927. Archived from the original on 13 November 2026. Retrieved 13 November 2026.
  20. ↑ AMEU 1936, p. 111.
  21. ↑ AMEU 1936, pp. 106, 146–147.
  22. ↑ National Archives of South Africa, NAAIRS catalogue, TAB, WLD, reference 239/1940, part 1: "Opposed application. Douglas Herbert Leibbrandt versus South African Railways and Harbours" (1940).

Sources

Further reading