Electric Railways, 1880-1990
This book presents a thorough survey of electric railway development from the earliest days of the London Underground to modern electrified mainline trains.
Inspec keywords: diesel-electric locomotives; AC-DC power convertors; rectifying circuits; history; railway electrification
Other keywords: signalling system; diesel-electric traction; power supplies; lateral power semiconductor controls; line train; economic electrification; electric railway history; diesel-electric railway systems; wireless electrification; mercury arc rectifier
Subjects: Other general electrical engineering topics; Power convertors and power supplies to apparatus; Transportation; Power electronics, supply and supervisory circuits
This book concentrates on electric traction, and the stress is on signalling developed for electric rather than steam railways, but there was considerable exchange of practice between the two. The most extensive, modern signalling and communications systems were found on new lines because they were not trammelled by established practice. Modern electric signalling, communications and control were introduced, perfected and integrated into an evolving whole in new electric railways or on steam railways that were electrified.
The period between 1790 and 1840 witnessed the experiments of Volta, Galvani, Oersted, Ampere, Faraday, Barlow, Jacobi, Henry, Elias, Froment, Davenport, Page and others. These pioneers produced primitive, low-powered motors, of uncertain reliability, which used batteries to produce motion, by rotation of a shaft, the oscillation of a lever, or the reciprocation of a rod. Major steps towards a successful motor were Barlow's spur wheel motor (1826), Henry's oscillating or rocking motor (1831), and the motors of Jacobi (1834), Elias (1842), and Froment (1845). Important research into magneto-electric generators and motors was carried out by Pixii (1832), Wheatstone and Cook (1845), William Scoresby and James Prescott Joule (1846). By the 1840s, powered locomotion had been widely demonstrated with models, boats and wheeled vehicles. The idea of electrical motive power gained in credibility when improved engines were produced after 1840.
A.G. Bell, T.A. Edison, G. Stephenson, J. Watt, H.S. Maxim, F.J. Sprague, Z.T. Gramme, W. Siemens, G. Marconi, S. de Ferranti, G.W. Westinghouse and H. Ford are examples of men who gave the world new engineering systems and components. Sprague, more than any other, created the heavy-duty electric railway, as distinguished from the electric street tramway, or the first electrified main lines on steam railways. The considerable achievements of Siemens, Westinghouse, van de Poele, Brush, Daft, Edison, Crompton, Thomson, Hopkinson, Houston and other pioneers are likewise acknowledged. These pioneers turned the electric street railway of 1880 into the electric heavy-duty railway of 1900. The earliest efforts to electrify tramways were done in ignorance of electrical engineering.
J.J. Heilmann systematically investigated various electrical systems and com ponents with a view to general railway electrification. He worked at the same time as F.J. Sprague but he did not focus to the same extent on rapid-transit systems, though he considered them. He invented the thermal-electric locomotive, and several of those who worked with him were to contribute to electric traction and the use of the internal combustion engine on railways.
The early British electric lines used simple DC system including the City & South London Railway, the Liverpool Overhead Railway, and both the Waterloo & City Railway and the Great Northern & City Railway. Later, these lines were supplied from AC stations when the electric railway network grew sufficiently large to justify large, centralised power houses and when the advantages of AC generation and transmission were recognised. Many electric street tramways continued to be supplied from DC stations until they were replaced by motorbus services, In Britain, the first DC electric lines ran in tunnel under great cities and there was a fear that return currents passing through the ground might damage buried cables and pipes, and an insulated fourth rail was often provided to carry it. It helped to meet the Board of Trade requirements that voltage drop be kept within limits, and was also used to leave the running rails free to carry track circuit currents for working automatic signals. This four-rail system was used on the Mersey Railway and on the London Underground lines, though at first the Central London Railway did not use it. It became standard in London Transport days.
The success of the first electric railways in London suggested to the general purpose railway companies that electric traction might suit the extensive and heavily used urban and suburban networks radiating from the larger London termini, particularly Waterloo, London Bridge and Liverpool Street.
The first electric rapid-transit railways, whether elevated on viaducts over streets as in Chicago or New York, or running in tunnels as in London, faced peculiar problems in the matter of signalling, position monitoring and control. The problems were acute with the tunnel lines, but they could be severe on the twisting elevated lines which curved sharply between the high walls of tenements and warehouses. There was no long-distance sighting ahead of trains, as there was on main lines, and braking distance often exceeded sighting distance. In the early 1890s, the steam-worked rapid-transit railway had reached a practically unsurpassable limit, and electrification was the only means of upgrading performance. This demanded an improved signalling and control system. Manual-mechanical signalling systems were improved and used on electrified rapid-transit railways, but the trend was to integrate signalling, communications and control more closely with the traction system and power supply. Automatic operations were introduced, and the survival of manual working became dependent of electro-mechanical aids and the powered working of distant mechanisms. This was made easier by ready access to electricity supply which was available in the large cities where rapid-transit railways were located.
Between 1890 and 1920, several examples of electric railway were constructed to serve different needs. There were rapid-transit railways, terminus lines, mountain railways and electrified main lines. There was no standard system of electrification and power supply, and no way of telling which system was likely to meet future circumstances better than the others. The relative advantages and dis advantages of the several kinds of motor, and of systems for converting power supply to traction current were matters of debate. There was considerable devel opment of systems for converting AC into DC, and for controlling and mount ing traction motors and transmitting their power. The advantages of using high-voltage AC for the power supply from generating stations to the railway feeder points was recog nised in the 1890s. The good traction characteristics of the low-voltage DC motor were equally evident. The attempts to combine the most efficient power supply with the traction motor with the best characteristics for a particular service resulted in several systems for electrifying railways. Before the mid-1920s the mercury rectifier was not available for large powers, so that conversion and frequency changing was by rotary converters mounted in lineside substations or on the locomotive. These methods defined the form and performance of the systems dependent on them. In this chapter, the main systems are each reviewed in turn.
Heilmann's 'Electric Rocket' established the thermal electric locomotive as a means of electrifying railways without fixed works, and the advantages of using an oil engine to drive the dynamo rather than a steam engine were clear.
Rectifiers were not needed when the light street railways of Europe and the USA were electrified in the 1880s using low-voltage DC supplied from batteries or dynamos in small lineside power houses, fn the 1890s, the first heavy-duty rapid transit railways were powered from DC generating stations which supplied power to conductor rails, or overhead contact wires. Rectifiers were not required for small projects such as the electrification of the Mersey Railway, Liverpool, in 1903. The need for rectifiers arose when small DC power houses were replaced by fewer large AC stations, which supplied AC transmission lines. The rectifier linked the AC supply with the low-voltage DC conductor rail. The development of the HVDC railway increased the demand for rectifiers which were generally rotary converters of the same design as those used on LVDC railways. The principle of the static rectifier was known by 1910, but the first experimental 'bulbs' were too expensive, too unreliable and too low in power capacity. The rotary converter was established, reliable, and long-lasting. Before 1930, it was able to convert powers far in excess of any practical battery of mercury-arc rectifiers. Rectifiers were also needed on many AC railways, to reduce the supply frequency to that of the AC motors.
The history of signalling, communications and control records many innovations which were tried long before they became common practice. The City & South London Railway (1890) and the Liverpool Overhead Railway (1893) used automatic signalling years before it became usual on general-purpose railways, and the London Post Office Railway demonstrated automatic working of an electric railway some 40 years before urban rapid-transit systems employed it. The Post Office Railway ran driverless trains carrying mailbags over 23 miles of track along a route 6.5 miles long. Passengers were not carried. It was the first automatic electric railway in the world, and was of great engineering significance. There were automatic and semi-automatic mechanical railways through out industry. Typically, wagons were hauled by a chain or cable from a quarry or mine to an unloading staithe or furnace. Many of the operations were controlled by trips or governors, and there was human intervention, as necessary, by an overseer. When labour was cheap, fully automatic operation was not economically justified.
By 1920, electric traction was well established on rapid-transit railways, tunnel lines, mountain railways and sections of main line railway in difficult terrain. These electric railways opened during the period when railway transport enjoyed a near monopoly on land for passenger traffic and long-distance goods movements, though after 1920 competition came from road transport when the state encouraged demobilised soldiers to set up motor bus and road haulage companies to create the motor-vehicle expertise which would be needed in a future war. Air transport using airships or aeroplanes was recognised as a potential threat.
Confronted by the success of General Motors, the steam locomotive builders tried to enter the field themselves. In 1940, with the 'Steamotive' a failure, General Electric and Alco co-operated to produced a 2000 hp AIA AIA diesel locomotive, but the entry of the USA into the World War in December 1941 brought government restrictions on further development. General Motors got all contracts for road (main line) diesels, and General Electric and Alco were limited to producing 1000 hp road-switchers. This restriction greatly hindered the efforts of Baldwin, Lima, and Alco to get into the business of diesel locomotive manufacture. Later, General Electric broke its link with Alco in order to manufacture diesels independently. The American Locomotive Company (Alco) did not have the resources of either General Electric or General Motors to continue diesel development and construction on its own, and it stopped build ing locomotives. It survived as Alco Products, making pressure vessels, pipe work, oil rig equipment and domestic equipment like washing machines. Another big manufacturer of steam locomotives, Baldwin-Lima-Hamilton started making diesels late, lacked a standard design, and suffered from the use of an inferior engine. In volume of diesel sales in the USA, the Baldwin group never held better than third place, after General Motors and Alco-General Electric. It met the same fate as Alco.
Three main classes of 'rectifier locomotive' using mercury-arc rectifiers were envisaged, converting AC to DC, AC to AC, and DC to AC. The term 'rectifier' became associated with the static or mercury-arc equipment, and 'converter' became the label for the rotary system. A contemporary review (in Railway Gazette, 1935) refers to pioneer designs of 1925.
Several schemes for railway electrification were proposed between 1920 and 1956 when the modernisation plan for British Railways was published. There were four reports on railway electrification submitted to the government between 1920 and 1951. Each one built on earlier work and each recommended that national railway electrification should use the HVDC system for main line work, and retain the LVDC 'London Standard' system for extensions to existing rapid transit networks.
The history of the many post-war developments in Europe falls into distinct phases. There was the period of reconstruction of war damaged plant, during which essential repairs were made and worn-out equipment was replaced. Between 1945 and 1955, there were severe financial restrictions on European economies, and priorities in industry were given to strategically important products. Britain gave priority to military matters in view of the country's global responsibilities at a time of confrontation with the Soviet Union. In Britain, certain railway projects implemented during the period 1945-55 were schemes which had been started before the war and then suspended until the late 1940s or early 1950s. The economic depression of the 1930s, the war, and the post-war recovery period delayed some projects by 15 to 20 years. Electrification schemes (LVDC) of the Southern Railway; the HVDC electrification of the LNER Manchester-Sheffield line over Woodhead; and several projects for upgrading power supply systems, substation equipment and signalling come under this category.
Large British general manufacturers like English Electric, or General Electric (GB) were well established in the business of electrifying railways and supplying electrical equipment to industry. These manufacturers were well placed to build diesel, gas-turbine and electric locomotives should British Railways need them. These general manufacturers urged the home railways to order diesel and electric locomotives to create a home market within which British industry could develop the skills required for winning foreign orders.
The main line alternating current traction in Britain is discussed. In the early 1950s, when the comparison between the HVDC and the AC system was made there was anxiety about the clearances which the HVAC system required for safety.
The single-phase 25-kV, 50-Hz railway became a global standard because of rectifier locomotives with DC motors. Without them, HVDC railway would have remained the standard and might have evolved into a 6000-V DC railway as the Russians proposed. The position of the AC system was helped by solid-state power electronics systems, which of course can also improve DC alternatives. Solid state rectifiers and thyristors greatly improved the performance of the rectifier locomotive and dispensed with the troublesome mercury-arc rectifiers.
This chapter discusses centralised control on railway signalling networks from 1965-1985.
This chapter discusses the single-phase AC electric mainline railway that linked London Euston to Crewe, Manchester and Liverpool. This first phase of the West Coast Main Line (WCML) electrification marked a culmination and a beginning. It was sometimes described as 'the former steam railway improved by electric traction and the dieselisation of non-electric operations'. Steam traction was surpassed in every way, but the railway's commercial and economic functions dated from the pre-electrification period.
