railway technology today 3 (edited by kanji wako) …jrtr.net/jrtr16/pdf/f48_technology.pdf ·...

48 Japan Railway & Transport Review 16 • June 1998

Technology

Technolo gy

Copyright © 1998 EJRCF. All rights reserved.

Railway Technology Today 3 (Edited by Kanji Wako)

Railway Electric Power Feeding SystemsYasu Oura, Yoshifumi Mochinaga, and Hiroki Nagasawa

Introduction

Electric power technology in the railwayindustry refers to the means of supplyinggood-quality electric power to the elec-tric motors. It primarily consists of powerconversion technology at sub-stations,feeding circuits for DC and AC feedingsystems, and the structure, materials, mea-surement, and maintenance of the elec-tric overhead lines.Power collection via the overhead lineand pantograph, introduced nearly 100years ago early in the history of electricrailways, remains basically unchanged inphysical appearance. However, techno-logical developments during the past cen-tury have done much to greatly increasethe current capacity, speed, and safety.Today, the capacity is more than sufficientto drive modern super high-speed trains.This article discusses all aspects of elec-tric power supply systems for railways,ranging from the history of electrificationof Japanese railways to today’s sophisti-cated power supply facilities. It also com-pares them with their counterparts in othercountries.

World RailwayElectrification Systems

Table 1 shows various feeding systemsaround the world and the electrificationdistances.The history of electric railways dates backto 1835 when T. Davenport fabricated amodel electric car powered by voltaiccells and put it on public exhibition. Thefirst practical electric cars debuted in 1879when a 150-V dc, 2.2-kW, bipolar motorpulled three passenger cars at a maximumspeed of 12 km/h at the Trades Exhibitionin Berlin. In 1881, Siemens Halske builtthe world’s first electric railway inLichterfelde marking the first passengerelectric railway.Electric operation is often preferred on

System TypeJapan1

km % km %

World (including Japan)

Main Countries

Notes: 1 Statistics include Japanese subways and AGTs.2 Kazakhstan is 3,528 km (3,000 V dc and 50 Hz 25 kV ac) but details are not known.

DC

Single-phaseAC

Three-phase AC

Unknown

Total

Less than 1,500 V 915 5 Germany, UK, Switzerland, USA

1,500 V to 3,000 V(Mostly 1,500 V) France, Spain, Netherlands, Australia

5,106 2

10,484 61 22,138 9

3,000 V or more(Mostly 3,000 V) Russia, Poland, Italy, Spain, South Africa78,276 33

50 Hz •

60 Hz

Less than 20 kV

20 kV

France, USA245 0

3,741 22 3,741 2

25 kV Russia, France, Romania, India, China2,037 12 84,376 36

50 kV USA, Canada, South Africa1,173 0

25 Hz • 11 kV to 13 kV USA, Austria, Norway1,469

120

1

16.66 Hz Switzerland011 kV

15 kV Germany, Sweden, Switzerland35,461 15

Switzerland, France30 0 43 0

Kazakhstan2, France3,668 2

17,207 100 235,816 100

Sources: (1) Railway Electrical Engineering Association of Japan, vol.8, no.10, pp.3–5, Oct. 1997(2) Ibid., vol.8, no.11, pp. 77–78 and pp. 81–83, Nov. 1997

Table 1 World Electric Railway Feeding Systems and Electrified Distances(1996)

railways with many long tunnels or onunderground railways because the energyefficiency is higher than steam or diesellocomotives and does not involve on-board combustion. The high tractive forcealso makes electric operation suitable forlines running through hilly regions. As aconsequence, electric train operationmade remarkable progress. It started firstwith direct-current feeding systems ca-pable of driving a DC motor directly andoffering high tractive force and easy speedcontrol.Although a 3000-V dc feeding system iswidely used in many other countries,some Japanese railways using DC rely ona 1500-V dc system.The other alternating-current feeding sys-tem originated in Europe using a single-phase, commutator-type motor. Speciallow frequencies such as 25 Hz and 16.66Hz were introduced in Austria, Germany,

and other countries to minimize rectifi-cation failures. Later advances in siliconcommutator technology paved the way forAC feeding systems using commercial fre-quencies in France and elsewhere. The25-kV system is used widely around theworld while Japan relies on a 25 kV sys-tem for shinkansen and a 20-kV ac feed-ing system for ‘conventional’ railways. (Inthis article, ‘conventional’ means all JNR/JR narrow-gauge lines, all non-JR railways,and the Akita and Yamagata shinkansen,which were converted to standard gaugefrom narrow gauge.)The three-phase, alternating-current feed-ing system is used with induction motorsin Europe for railways with steep moun-tain grades, while a 600-V system, featur-ing speed control by a power converter,is used in Japan for new urban transit sys-tems.

49Japan Railway & Transport Review 16 • June 1998Copyright © 1998 EJRCF. All rights reserved.

History ofRailway Electrification in Japan

Commercial operation of electric railwaysin Japan dates back to 1895 when a 500-V dc tram system was started in Kyoto.The first electric railway owned by theJapanese Government Railways began op-eration in 1906 between Ochanomizuand Nakano in Tokyo, which used to be-long to Kobu Railways before being pur-chased by the government. The 600-Vdc system was later replaced by a 1200-V dc system to prevent voltage drop. In1922, it was replaced again by a 1500-Vdc system when the section betweenYokohama and Kozu was electrified. The1500-V dc system is still used today byall DC electric railways in Japan.The postwar increase in transportationdemand in Japan led to the introductionof more powerful electric locomotivesaround 1950. At that time, it was fearedthat the 1500-V dc system had reachedits limit, and a study was started on rail-way electrification based on commercial-frequency, single-phase alternatingcurrent. After a successful demonstrationtest on the Senzan Line, the first commer-cial operation using an electric locomo-tive started in 1957 on the Senzan andHokuriku Lines, soon followed by a 20-kV single-phase, alternating-currentsystem using a step up or boosting trans-former (BT) to minimize inductive inter-ference in telecommunication lines.In 1964, the Tokaido Shinkansen beganoperations using the BT feeding system,marking the first high-speed train opera-tion with a maximum speed of 210 km/h.However, it soon faced maintenance andother technical problems associated withthe large collection current requiring com-plex anti-arcing designs. This led to astudy of the auto transformer (AT) feedingsystem, which was introduced on theYatsushiro-Nishi Kagoshima section of theKagoshima Line in 1970, and on the ShinOsaka–Okayama section of the Sanyo

Shinkansen in 1972. Today, the AT feed-ing system is the standard for all AC elec-tric railways in Japan.Figure 1 shows the history of railway elec-trification in Japan from the era of the Japa-nese Government Railways until thepresent JRs. Figure 2 maps the varioussystems in Japan. Roughly speaking, the1500-V dc system is used on the conven-tional railways in Honshu (Kanto, Tokai,Kansai, and Chugoku districts) andShikoku, while the 20-kV ac system ismainly used in Hokkaido, northernHonshu (Tohoku and Hokuriku districts),and Kyushu. All shinkansen use the 25-kV ac system. In contrast, most privaterailways rely on the 1500-V dc system,while the 600- or 750-V dc system is usedby subways and some other railways.

Various Feeding Systems

From power station to railwaysub-stationThe electric power generated by powerstations is carried to electric railway sub-stations by transmission lines. JR East has

its own hydroelectric power station inNiigata Prefecture (on the Shinano River)as well as a thermal power station inKawasaki City in Kanagawa Prefecture.These two power stations supply the rail-ways in the Tokyo metropolitan area.In Japan, the receiving voltage at sub-stations for direct-current electric railwaysis usually extra-high tension at 22, 66, or77 kV. This is converted to 1200 Vby a transformer, and then to direct cur-rent by a rectifier at the rated voltage of1500 V (no-load voltage of 1620 V). Sub-ways and some private railways use 600or 750 V dc.The receiving voltage for alternating-cur-rent conventional electric railways is anextra-high voltage of 66, 77, 110, or 154kV. The shinkansen use receiving volt-ages of 77, 154, 220, or 275 kV. The con-ventional railways use a feeding voltageof 20 kV, and the shinkansen use single-phase at 25 kV.

Figure 1 History of Railway Electrification in Japan*

1906 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995

Year

2,000

4,000

6,000

8,000

10,000

12,000

0

20

40

60

0

Elec

trific

atio

n Ra

tio (%

)

Elec

trifie

d Di

stan

ce (k

m)

Shinkansen2,036.5 km

Conven-tionalrailways9,897.3 km

Electrification ratio53.9%

ShinkansenAC, Conventional railwaysDC, Conventional railways

Electrified Distance

JNR 10-year Financial Restructuring Plan

3rd Long Range Plan2nd 5-year Plan

1st 5-year Plan

Conventional railways AC electrification3,682.3 km

Conventional railways DC electrification6,215.0 km

Electrification ratioElectrified distance

Note:* Including Japanese Government Railways, Japanese National Railways (JNR, from June 1949

to March 1987) and JRs, but excluding private railways


Technology


Asahikawa

Kushiro

Hakodate

Muroran

Aomori

Morioka

SendaiFukushima

Utsunomiya

Nagoya

KochiOita Tokushima

Wakayama

Hiroshima

Gifu

Akita

YamagataamagataNiigata

Murakami

ItoigawaKanazawaFukui

Kyoto

Kinosaki

Nagahama

Tottori

Shin-Osaka

Fukuyama

Hakata

Kumamoto

Miyazaki

Shingu

Nagasaki

Iyoshi

Kokura

Nishi Izumo

Sasebo

Kagoshima

Okayama

Nagano

Kofu

Shizuoka

OmiyaToride

Kuroiso

Tokyo

HimejiHimeji

Otaru

Asahikawa

Kushiro

Hakodate

Muroran

Aomori

Morioka

SendaiFukushima

Utsunomiya

Nagoya

KochiOita Tokushima

Wakayama

Hiroshima

Gifu

Akita

YamagataNiigata

Murakami

ItoigawaKanazawaFukui

Kyoto

Kinosaki

Nagahama

Tottori

Shin-Osaka

Fukuyama

Hakata

Kumamoto

Miyazaki

Shingu

Nagasaki

Iyoshi

Kokura

Nishi Izumo

Sasebo

Kagoshima

Okayama

Nagano

Kofu

Shizuoka

OmiyaToride

Kuroiso

Tokyo

Himeji

Otaru

Conventional Railways

DC

AC

Shinkansen

Figure 2 Map of Railway Electrification of JR Group in Japan

DC feeding systemA direct-current feeding system features athree-phase bridged silicon rectifier forconversion from alternating to direct cur-rent. Since the three-phase rectifier uses a6-pulse system, it causes lower harmonicsin the AC side and distortion in the voltagewaveform, lowering the power quality. Toreduce the harmonics, a more-modern rec-tifier design using a 12-pulse system fea-turing two sets of 6-pulse rectifying circuits,with AC input voltage phases 30° apart,connected in series or parallel, is used.Figure 3 is an example showing the struc-ture of a DC feeding circuit connected tothe nearest sub-station. Section and tieposts are sometimes used to prevent volt-age drops on double tracks where sub-stations are located far apart. In this case,the up and down tracks are connected by

Figure 3 Structure of a DC Feeding System

6-pulse Rectifier

3-phase AC

3-phase AC

High-speedcircuit breaker

Sectioningpost

1,500 V dc 1,500 V dc– + – +

Transformer

Rectifier

Transformer

Rectifier

Electric car Rail

Contactwire

Feeder

Three-phase ACThree-phase AC12-pulse Rectifier


a high-speed circuit breaker. The distancebetween sub-stations is about 5 km onmetropolitan trunk lines and 10 km onother lines.Efforts are being made to introduce regen-erative cars on DC electric railways inorder to reduce the weight and save en-ergy. They are designed to convert thekinetic energy into electric power duringdeceleration and return it to the overheadlines. However, the regenerated powerwould be wasted if there are no cars inthe section to use it. This loss can be pre-vented by thyristor rectifiers, thyristor in-verters, thyristor chopper resistors, orsimultaneous up and down track feedingsystems. Such devices are used on somesections; Figure 4 shows an example of athyristor inverter. In this system, the mo-tive power is supplied from a rectifier, andwhen the regenerative power exceeds themotive power requirement, the inverteris activated automatically to supply powerto stations, etc.

AC feeding systemSince three-phase power from the powerutility is converted to two single phases,to ensure that the current is as close aspossible to the three lines of the three-phase side, one separate phase is fed toeach of the overhead up and down tracks.Various methods can be used to connectthe feeding transformers. Today, the Scottconnected transformer (Fig. 5) is used toreceive extra-high tension, and the modi-fied wood-bridge connected transformer(Fig. 6) is used to receive extra-high volt-age, with the neutral point directlygrounded.Figure 7 shows the composition of an ACfeeding circuit. It includes feeding ACsub-stations, sectioning posts for feed sec-tioning, and sub-sectioning posts for lim-ited sectioning, all located along thetracks. The feeding sub-stations feed thetwo single phases converted from thethree-phase source by a feeding trans-former in the opposite track directions,

ST

A phaseEarth

T

ST: Step up transformer

B phase

F

O

V

UW T F

Figure 5 Scott ConnectedTransformer

Figure 6 Modified Wood-bridgeConnected Transformer

Feed to overhead line (UVW is 3-phase and TF is 1-phase)

V

Main phase transformer

T F (N)

U W

T

Teaser transformer

F (N)

Figure 4 Power Regeneration by Thyristor Inverter

Figure 7 Structure of an AC Feeding System

Station facilities, etc.

1,500 V dc

HarmonicfilterRegenerative

inverter

Regenerative car

Distributiontransformer

Rectifier

Transformer Transformer

3-phase 6.6 kV ac bus

Three-phase AC

Feedingsub-station

SS

Feedingsub-station

SS

SSPSP

: Circuit breaker: Air section

: Disconnecting switch: Phase-to-phase changeover section

Down track

Up track

Sub-sectioning

postSSP

Sub-sectioning

post

Sectioningpost


Technology


with a 90° phase offset.Table 2 shows the feeding voltages andthe distances between sub-stations of vari-ous AC feeding systems in Japan.

BT feeding systemFigure 8 shows the composition of a BTfeeding circuit. A BT is installed every 4km on the contact wire to boost the re-turn circuit current on the negative line.

This design minimizes the inductive in-terference on telecommunication linesbecause the current flows to the rail onlyin limited sections.In particular, when an electric car passesa BT section, a large arc is generated inthe section, and a large load current cancause a very large arc that can damagethe overhead line. Consequently, capaci-tors are often inserted serially in the nega-

tive feeder to compensate for the reac-tance and reduce the amount of currentintercepted by the pantograph, thereby re-ducing arcing, and also helping to pre-vent voltage drop.

AT feeding systemIn the AT feeding system, the feeding volt-age of the sub-station is twice the voltagesupplied to the electric car. An AT, atevery 10 km along the track, cuts the volt-age to the overhead-line voltage as nec-essary. This is very effective in reducinginductive interference in telecommunica-tions lines. Figure 9 shows the composi-tion of an AT feeding system, and thephotograph below shows an external viewof an AT designed for shinkansen.In Japan, the AT is designed with a turn ra-tio of 1:1 and the sub-station feeding volt-age is twice the overhead-line voltage. Thissystem is ideal for high-speed and large-capacity electric cars because there are nolarge voltage drops nor arcing sections.

Coaxial cable feeding systemAs shown in Figure 10, the coaxial cablefeeding system features a coaxial cablelaid along the track. Every several kilo-meters, the inner conductor is connectedto the contact wire and the outer conduc-tor is connected to the rail. The cableitself is very expensive but the conductor

Figure 8 Structure of NF-based BT Feeding System

External view of AT (60/30 kV, 7500 kVA) (RTRI)

V

II

Sub-station NF capacitorNegativefeeder

Contactwire

Rail

BT section

Boostingtransformer(BT)

Boostingwire

Electric car

Feedingsystem

Feeding voltage (kV)

Conventionalrailways

22

Shinkansen

—

Conventionalrailways

30 to 50

Shinkansen

—

Distance between sub-stations (km)

BT

44 60 90 to 110 20 to 60AT

— 30 — 10Coaxial

Table 2 Feeding Voltages and Distances between Sub-stations ofVarious AC Feeder Systems in Japan

Figure 9 Structure of AT Feeding System

I/2I

2VV

V

Sub-station Auto transformerContactwire

Protectivewire

Rail

Feeder

Electric carCPW

AT ATAT


layout is simple, making it ideal for usewhere space is limited. Japan is the onlycountry that uses this system (the Tokyosections of the Tohoku Shinkansen andTokaido Shinkansen).In comparison to the overhead line, thecoaxial power cable has an extremelysmall round-trip impedance. Therefore,the load current is boosted in the coaxialpower cable from the connection with theoverhead line. This results in a rail cur-rent distribution similar to that of the ATfeeding system, significantly reducing theinductive interference in telecommunica-tion lines.

Detecting Feeding Faults

Feeding circuit faults can be caused byelectric car faults, overhead line faults, fly-ing objects, and animals (birds, snakes,etc.). The high voltage causes a high faultcurrent and, consequently, a protectiverelay is used to instantly detect any faultand trip a power circuit breaker.

DC feeding systemIn a DC feeding system, typically, the cur-rent for the electric car increases smoothly,but a fault current always increasesabruptly. A ∆I-type fault selective relay atsub-stations is used to detect faults basedon this difference.

AC feeding systemIn an AC feeding system, faults are de-tected by a combination of a distance re-lay and an AC ∆I-type fault selective relay(Figure 11). The distance relay monitorsthe overhead line impedance from thesub-station and recognizes an event as afault when the impedance falls within apredetermined rectangle on the imped-ance plane. As with DC systems, the AC∆I-type fault selective relay detects thechange in current.Furthermore, locators are used to mark faultpoints based on the current distribution,so any fault can be corrected promptly.

Overhead Line Systems

Catenary systemAn electric railway takes its power for theelectric motors, lights, air conditioning,etc., from the overhead line using the pan-tograph on the roof.The pantograph is in constant contact withthe overhead line (contact wire) locatedabout 5 m above the rails, whether thetrain is moving or not. Therefore, the over-head line must always be located withinthe pantograph range, and the pantographmust always maintain contact with theoverhead line to supply uninterrupted,good-quality power at all times. To meetthese requirements, the overhead equip-ment is generally designed bearing thefollowing in mind:• Must have characteristics meeting train

speed and current requirements• Must be at uniform height above rail to

optimize pantograph power collectingcharacteristics, so entire equipmentmust have uniform spring constant andbending rigidity

• Must have minimum vibration and

Figure 10 Coaxial Cable Feeding System

Figure 11 Protective Zone of AC Electric Railway Protective Relay

I

I

V

Sub-stationCoaxial powercable

Negative feeder

Contact wire

Rail

Electric car

Impedance of contact line

Distance relay

SP

SS

∆l relay

Resistance

SS: Sub-stationSP: Sectioning post

Rea

ctan

ce

PWM controlling car Powering

Thyristo

r contro

lling ca

r

Powering


Technology


Item JapanTGV Southeast

France

TGV AtlanticGermany Italy

Catenary type Heavy compound type Stitched and simple Simple Stitched and simple Twin stitched and simple

Standard span [m] 50 63 (Stitched wire 15) 63 65 (Stitched wire 18) 60 (Stitched wire 14)

Standard wire height [m] 5.0 4.95 4.95 5.3 4.85

System height [mm] 1,500 1,400 1,400 1,800 1,400

Suspended St 180 mm2

(1.450 kg/m)Bz 65 mm2 (0.59 kg/m)

Bz 65 mm2 (0.59 kg/m)

Bz11 70 mm2

(0.63 kg/m)CdCu 153.7 mm2

(1.42 kg/m)

Wiregrade Auxiliary suspended Cu 150 mm2

(1.375 kg/m)Bz 35 mm2 — Bz11 35 mm2

(0.31 kg/m)(0.30 kg/m)

Contact wire Cu 170 mm2

(1.511 kg/m)CdCu 120 mm2 Cu 150 mm2

(1.33 kg/m)CuAg Ri 120 mm2

(1.08 kg/m)CuAg 151.7 mm2

(1.35 kg/m)

Contact line total density [kg/m] 4.34 1.65 1.92 1.71 2.77 × 2

Catenarywiretension

Suspended [N] 24,500 14,000 14,000 15,000 18,400

Auxiliary suspended[N]

14,700 4,000 (Stitched wire) — 2,800 (Stitched wire) 2,900 (Stitched wire)

Contact wire [N] 14,700 14,000 20,000 15,000 14,700

(Total tension) [N] (53,900) (28,000) (34,000) (30,000) (33,100 × 2)

Wave propagation velocity of contact wire [km/h]

355 414 441 424 376

β (train speed/ wave propagation velocity)

0.68, 0.76(= 240, 270/355)

0.65 (= 270/414) 0.68 (= 300/441) 0.59 (=250/424) 0.66 (= 250/376)

Pre-sag None 1/1,000 1/1,000 1/1,000 1/1,000

Table 3 Comparison of Overhead Line Constants on Dedicated High-speed Lines

5.0 m

15 m 15 m

63 m

9.0 m

2 23.5 3.53.5 3.54.5 4.5 4.5 4.5

50 m

Shinkansen German high-speed line

65.0 m

60 m

6.0 m1 m

9.0 m

18.0 m 18.0 m

5.0 m 1.8 m

French TGV Southeast

French TGV Atlantic

Italian high-speed line

1.4 m

Figure 12 Overhead Lines of World High-Speed Railways


motion to ensure smooth pantographpassage during high-speed operation orstrong winds

• Must have strength to withstand vibra-tion, corrosion, heat, etc., while main-taining balance with reliability andoperating life span

Figure 12 compares the catenary equip-ment for high-speed trains in differentcountries. In Japan, compound catenaryequipment consisting of three longitudi-nal wires is used for shinkansen, whilesimple or stitched catenary equipment isused in Europe. The Italian high-speedline uses twin catenary equipment to sup-ply the large current for the 3-kV dc elec-trification. Table 3 compares the constantsof these various catenary systems.Compound catenary systems feature lesspantograph vertical motion and largercurrent capacity but require a larger num-ber of components resulting in a morecomplex design.In Europe, pre-sag is often used to com-pensate for the large vertical motion of thepantograph in the simple catenary system.Pre-sag refers to a special design feature inwhich the height of the contact wire islower at the centre of the span by anamount equal to around 1/1000 of the span.In real terms, generally, the contact wireheight is 20 or 30 mm lower than the sup-ports at the centre of the span, thereby sup-pressing the pantograph vertical motion.This design is effective for the overheadlines on the French and German high-speedlines which have a large amplitude, but isless effective for overhead lines with smallamplitudes like the shinkansen and the Ital-ian high-speed line.

Lateral wave propagationThe most critical constants for the me-chanical performance of the overhead lineare the weight and tension per unit length.The total tension is relative to the push-up force of the pantograph and is closelyrelated to the vertical motion of the over-head line. It is 54 kN for shinkansen and

28 to 34 kN for the French and Germansystems. The Italian system has a totaltension of 66 kN because it uses a twincatenary system with a larger wire size.The pantograph push-up force is roughly70 to 80 N for Japan, 130 to 250 N forFrance and Germany, and 200 to 300 Nfor Italy. This means France and Germanyhave an overhead line amplitude aboutfour times greater than that of Japan.Generally speaking, greater stability re-sults from smaller overhead line ampli-tude. It also reduces the fault frequencyand damage to components. The Frenchand German systems seem to allow largeramplitudes at the cost of fewer panto-graphs.The square root of the ratio of the contactwire tension to the weight per unit lengthrepresents the velocity of the lateral wavepropagating along the wire. This is the mostimportant parameter in overhead line de-sign. In railway technology, this velocity iscalled the wave propagation velocity andis recognized as the critical speed.Table 3 shows the wave propagation ve-locity and the ratio of the train speed tothe wave propagation velocity (β). Simu-lation and experiments have verified thatas the train speed approaches the wavepropagation velocity, the overhead lineamplitude and local bending increase,making it harder to maintain contact be-

tween the pantograph and overhead line.It is estimated that the resulting perfor-mance drop becomes apparent when thetrain speed exceeds 70% to 80% of thepropagation velocity. At this speed, lossof contact with the line increases greatly,and in extreme cases, the overhead lineitself can be destroyed.Consequently, the contact wire constantmust be set so that the propagation veloc-ity is significantly faster than the train speed.The propagation velocity can be increasedby laying a lighter wire at a higher tension.In the case of a pure copper contact wire,after considering safety factors, the maxi-mum achievable speed (neglecting wear)is around 500 km/h. Any further increasein the wave propagation velocity can onlybe achieved by using wires with a highertensile resistance per weight unit length.In Japan, wires in use or under develop-ment include copper alloys, and other al-loys, as well as compound wires such asaluminium-clad steel wire, and copper-clad steel wires.In Table 3, the β values are all 0.7 or lower,indicating that all countries have selectedvalues within the above-mentioned stablevelocity range for train speeds.The photograph (above left) shows a heavycompound overhead line. The Nagano-bound Shinkansen (Takasaki–Nagano sec-tion), which started operations in October

Heavy compound overhead line of Tohoku Shinkansen (RTRI) Simple catenary equipment of Nagano-boundshinkansen (RTRI)


Technology


1997, uses the simple catenary overheadequipment found commonly in Europe.This system was chosen for economy be-cause the less-frequent train operationconsumes only a small proportion of thecurrent-carrying capacity. This shinkansenuses a 110-mm2 copper-clad steel wire (Fig.15b) with a tension of 20 kN to withstandthe train operating speed of 260 km/h. Thisis the first simple catenary system for high-speed operation in Japan.

Third-rail conductorIn the third-rail conductor system, thecollector is laid next to the rail to savespace in restricted subways. This systemdates back nearly 70 years to 1927 whenit was first introduced on the Ginza Lineof the Tokyo Rapid Transit Authority(TRTA). The voltage is 600 or 750 V. Fig-ure 13 shows the structure. In Japanesesubway systems, it is shielded at the topand on one side for safety; a flat shoe col-lects current directly from the top of therail, which is supported by insulators ev-ery 2.5 to 5 m. This third rail system islimited to a maximum speed of around70 km/h due primarily to the undergroundconditions in the Tokyo metropolitan area.However, experiments show it is capableof serving speeds exceeding 100 km/h.

Overhead rigid conductor systemThe overhead rigid conductor system hasbeen developed as an overhead line fordirect links between subways and suburbanrailways. It features toughness and smallspace requirements (Fig. 14 and oppositephotograph) and prevents broken wires andother accidents, especially in the subwaysections.The maximum speed has been limited to90 km/h primarily due to the short dis-tances between stations and frequentcurves in the metropolitan subways.The system runs at a voltage of 1.5 kV toallow direct connections to suburban rail-way systems. It has been used for nearly40 years on the TRTA Hibiya Line.Overhead rigid conductor system and pantograph (RTRI)

Figure 13 Third Rail Arrangement

Tensionless

Wall (tunnel, etc.) Insulator

410 mm

6 m max.

T-shaped mountLong ear

Contact wire

Figure 14 Overhead Rigid Conductor System

Protective plate

Third rail(conducting steel rail)

Insulator

Running rails


Materials in Overhead Lines

The overhead line equipment consists ofthe contact wires, fixtures, and supports.The contact wire has a round cross sec-tion with grooves at the 2 and 10 o’clockpositions, used for hanging the wire froma fixture. Conventionally, contact wireshave been made of hard-drawn copper.Copper has very low electrical resistanceand excellent corrosion resistance, mak-ing it an ideal material for contact wires.To provide higher mechanical strength, softcopper is hard drawn into contact wires.In Japan, contact wires composed of cop-per with 0.3% tin are used widely to im-prove wear characteristics. Tunnelsections often use silver-copper alloy con-tact wires for extra heat resistance withthe aim of preventing broken wires dueto train fires. Recently, such copper-sil-ver alloy contact wires are being replacedby copper-tin alloy contact wires.A recent addition to the shinkansen arecopper-clad steel contact wires designedto increase the wire tension for higher-speed operation. Figure 15 shows crosssections of the conventional type, and thetwo variations: copper-clad steel, and alu- External view of diagnostic car for electric facilities (RTRI)

minium-clad steel.The messenger wire is often made of gal-vanized stranded-steel wire for economyand high mechanical strength. Hard-drawn copper stranded wires are also usedin many sections requiring larger currentcapacity.Messenger wire fixtures require high-strength and corrosion-resistant materials,such as stainless steel and copper alloy.Aluminium alloy is preferred where

weight reduction is critical.Supports are often made of galvanizedsteel. High-quality, inexpensive porcelaininsulators are common, but polymer in-sulators with excellent insulation charac-teristics have been introduced recently.

Maintenance of Overhead Lines

Overhead line inspection carsThe overhead line is a very long linearstructure and, as such, is subject to slid-ing stress from the pantograph. It is alsosubject to a stress due to rain, wind, snow,ice, and other natural phenomena. Con-sequently, the overhead line is a poten-tial source of accidents involving brokenwires due to corrosion and wear. Suchaccidents require many hours for repair,so maintenance is essential.Maintenance begins with accurate diag-nosis of the present condition of the over-head line, often performed from a movingcar. The shinkansen overhead lines areinspected every 10 days using ‘DoctorYellow’, a seven-car electric facilities andtrack diagnostic system (JRTR 15, p. 43).Conventional lines use a two-car system.The measured items include the contact

Figure 15 Contact-Wire Cross Sections

3 mm 3 mm 3 mm

(a) Hard-drawn copper (c) Aluminium-clad steel(b) Copper-clad steel


Technology


Feeder line inspection robot (RTRI)

Contact wire replacement work car (RTRI)

Hiroki Nagasawa

Dr Hiroki Nagasawa joined RTRI in 1972 after graduating in me-

chanical engineering from Tohoku University. He is engaged in de-

velopment of current collection systems, especially overhead line

materials. He obtained his Ph.D. in tribology from Tohoku University

in 1996.

Yasu Oura

Mr Yasu Oura joined JNR in 1967 after graduating in electrical engi-

neering from Shibaura Institute of Technology. He is Chief Manager

of the Technological Development Department at the Railway Tech-

nical Research Institute, which he joined in 1987.

Yoshifumi Mochinaga

Dr Yoshifumi Mochinaga joined JNR in 1967. He graduated in elec-

trical engineering from the Science University of Tokyo in 1980. He

is a Manager in the Power Supply Technology Development Depart-

ment at RTRI, which he joined in 1987. He obtained his doctorate in

AC feeding systems from the Science University of Tokyo in 1994.

Kanji WakoMr Kanji Wako is Director in Charge of Research and Development at RTRI. He joined JNR in 1961 after graduating in engineering from Tohoku University. He is the supervising editor for this

series on Railway Technology Today.

wire height above rail, deviation, wear,acceleration of pantograph head, and con-tact loss. For shinkansen, the measureddata are processed by a central computerand the results are sent to the relevantmaintenance crews.Some items cannot be checked from amoving car. These include corrosion ofthe feeding wires and loose screws, whichare inspected manually during normalmaintenance work.When lines need replacement, the work isperformed using special cars. The abovephotograph shows a six-car system de-signed to replace shinkansen contact wires.Automated diagnosis and repair is a re-cent topic for railway engineers and spe-cial efforts are being made to developrobots for this purpose.

RoboticsOverhead line systems require dangerouswork at height. A self-powered feedingline robot with eddy current sensors hasbeen developed and put into operationto locate cross-sectional area loss due tocorrosion. �

railway technology today 3 (edited by kanji wako) …jrtr.net/jrtr16/pdf/f48_technology.pdf ·...

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