CE 515 Railroad Engineering

Railway ElectrificationAREMA Chapter

9

“Transportation exists to conquer space and time -”

Image: Ohio State University

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Electric Traction Development• 1835: Thomas

Davenport – developed electric railway using a model railroad with a third rail

• 1879: Werner von Siemens – first practical electric railway

• 1890: Siemens' brothers - London underground railway (two 50 hp motors)

• 1898: Arthur Koppel - introduced mass production battery and electric locomotive in the US

Image: Getty (under fair use)

Image: Scientific America Supplement

Image: Mike’s Rail History prior to 1935

Image: Mike’s Rail History prior to 1935

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Electric Traction Development• 1895: first electric

train in the US• Power was supplied

at 550 to 675 VDC• 1905: Railways

started using and converting DC to AC power with up to 25 kV• Example of power

used in the US:– High speed: 12.5 – 25 kV– Heavy haul: 25 – 50 kV– Commuter: 650 – 12 kV

• Most efficient found in 1960s was 25 kV

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Image: 1902, viewliner LTD

Image: City of Montreal

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Electric over Diesel-Electric• Straight-Electric Advantages:

– Higher speeds and low-end torque– Able to utilize multiple power sources (coal, nuclear,

hydroelectric)– Minimize local air emissions– Can employ regenerative braking to add electricity to

the grid – Can improve capacity without adding infrastructure

• Diesel-Electric Advantages:– Lower initial capital cost– Does not require elaborate electrical grid system– Can operate during any power state and in areas where

power cannot be reached easily– Minimizes electrical safety hazards to the public with no

exposed high-voltage rails or wires.

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Existing Electrification Systems• Inter-City

• Heavy Haul

• Commuter Rail

• Metrorail

• Light Rail

• Street Car

• Advance Light Rapid Transit

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Elements of an Electrification System

• Sources of primary power

• Substations to transform the power into a form suitable for train operations

• Power distribution system

• Current collectors to draw the power

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Sources of Primary Power• Railways will receive electrical power from

multiple sources– Coal, nuclear, hydroelectric

• Railroads rarely will generate own electricity• AC and DC power substations provide one

level of redundancy– Two transformers will power two different sections so

one can be taken offline for maintenance• DC substations use a rectifier transformer

to step down and convert AC power• Distribution system:

– Feeder cables (power distribution to contact system)– Negative return cables (attached to the rails)– Contact system

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Power Distribution Systems• Third Rail Power System– Rigid and mounted parallel to

the track on sleeper ties using an insulator

– terminated at rail crossings, turnouts, and diamonds

– Issues experienced include:• Icing, limited voltage, stray return

currents the leak into the ground

• Catenary Power System– Catenary wire and contact

wire(s)– One or two contact wires in

tension– Breaks allow for

maintenance– Return wire connected to

the rail complete the circuit

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Power Collection Systems• Contact Shoe–For third rail systems–Overrunning, under, and side

• Trolley Poles and Pantographs–For overhead catenary

systems–Single pole, diamond, z-

shaped–Consist of a wide carbon

rubbing strip–6 ft. 6 inches above the rain

with a 4 ft. 4 inch rubbing strip–High tension contact

In tension to preventPantograph oscillation

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Signals and Communication• Trains are detected

through electrical track circuits of the train control system• Signaling systems cannot

work if the rails are used as negative returns• An impedance bond

connects to the tracks across the insulated joint• Allows traction current to

pass through while keeping the signaling system track circuit separated

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