Introduction:
This page shows images of configurations and hardware used with the Chinese Overhead Line Equipment (OHLE).
By Chinese I mean to include all territories of China and all makes and types of OHLE.
Definitions:
kv - kilovolt, 1000 volts.
hz - hertz, frequency.
ac-alternating current.
dc- direct current.
The Chinese, and the Hong Kong Territories, have settled on the standard overhead traction supply voltage of 25 kv ac using the commercial frequency of 50 hz for all the mainline railways (not including trams and metros).
Why 25 kv 50 hz? Here is the very brief history lesson.............
The early railway electrification projects were a battle ground between the AC and DC camps.
AC offered very good transmission qualities but lacked a satisfactory means of controlling the traction motors. The commercial frequencies of 50 hz in Europe and 60 hz in the United States was to high and the motor control proved too difficult for the railway operating and maintenance requirements of the time period.
DC was very good for motor control but the traction motors use low voltages and high currents. The high currents in turn require a larger, heavier, and more expensive plan.
The ultimate system obviously was one that could use an AC traction power transmission system combined with a DC tractor motor control system. But that system would have to
wait for a few decades before a cost effective and reliable solution would evolve.
The first use of commercial frequency (50 or 60 hz) for mainline railway traction began in Switzerland in 1904 on the Seebach and Wettingen section of the Swiss Federal Railways. The equipment, provided by Oerlikon, used 15 kv ac at 50 hz. As with any new systems, the advantages were not immediately apparent and the line was later converted to 15 hz which was the norm for the period prior to the standard being declared 16 2/3 hz. [Ref. 2, pp 124]
The European standard was set at 15 kv ac using 16 2/3 hz, The number 16 2/3 is simply 1/3 of 50 hz.
The Westinghouse company in the United States settled on 11 kv ac 25 hz.
Moving ahead a few decades we arrive in the late 1930's in South West Germany on the Hollenthal railway line. The line was electrified with an overhead catenary system providing 20 kv ac at 50 hz. One of the many goals of the Hollenthal works was to investigate the possibility that new advances in the electrical engineer field could eliminate the need for the mechanical frequency converter stations (ac motor - ac generator) that converted the 50 hz commercial frequency to the 16 2/3 hz and the cost of new railway electrification projects could be significantly reduced. [Ref. 1, pp 247]
One of the locomotives being tested, number E244.11 by Brown-Boveri, had incorporated the
newly developed mercury-arc rectifier to convert the single phase ac supply to dc for use in the traction motors.
[Ref. 1, pp 248]
That was the ticket!
But that would have to wait as World War II had then taken a hold of Europe.
Move ahead now to late 1944 when the Allied Military Forces took over parts of Germany, the French made sure that the French Zone included the Hollenthal railway line. This move was very well thought out by such visionaries as Louis Armand. The French railways (SNCF) had already electrified portions of the French network using 1500 volts dc and the SNCF was seeking
alternatives to reduce the costs of railway electrification.[Ref. 2,Chapter 1]
Once the SNCF became more experienced with the Hollenthal line, the decision was made to increase the line voltage from 20 to 25 kv.
The SNCF then went to work electrifying the railways of the heavily industrialized Alsace and Lorraine regions of France using the 25 kv ac 50 hz system.
Thus, the SNCF is the source for the 25 kv ac 50 hz standard being used throughout the world today.
The areas of the world that use 60 Hz also followed the French model of using commercial frequency and adopted 25 kv 60 hz. For example, the Japanese New Trunk Line (Shinkansen).
For further reading, see the three references located at the bottom of this page.
|
References:
[1]"Electric Railways 1880-1990", 452 pages, by Michael Duffy,The IEE, Michael Faraday House, Six Hills Way, Stevenage, SG1 2AY, United Kingdom,2003, ISBN 0-85296-805-1.
Their website is: www.iee.org
[2]"On the Fast Track, French Railway Modernization and the Originsof the TGV, 1944-1983", 255 pages, by Jacob Meunier, Praeger Publishers, 88 Post Road West, Westport, CT 06881, 2002, ISBN 0-275-97377-8.
For further reading:
"Contact Lines for Electric Railways", 822 pages, by Friedrich Kiessling, Rainer Puschmann, Axel Schmieder, SIEMENS
Atkiengesellschaft, Munich, Germany, 2001, ISBN 3-89578-152-5.
Publisher, Publicis Corporate Publishing, Munich & Erlangen, Germany. Their website is: www.publicis-komm.de/books
I sourced my english lanquage version from Amazon Books.
|
