autotransformer system

Banebranchen Session 2012 May 9th - 2012

1

High Performance Railway Power

Introduction to Autotransformer system (AT)

Banebranchen – Session infrastructure May 9th 2012

Tommy O. Jensen/Atkins Danmark


2

Agenda

Historical

AT system ”reinvented”

Principle of operation

AT supply system

AT system at HSL-railways

AT system in SwedenAT system in Sweden

AT system in Norway

Advantages/drawbacks of AT

Suitable for use in Denmark?


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Introduction of AC-systems

Historical

1900 AC locomotives are introduced Ganzdevelops the first AC locomotive (3 kV)

1905 Many AC systems open in the eastern US, among others New York – New Haven (11 kV)

Valtellina 3 kV – 15

Hz, Italien1902

Haven (11 kV)

1910 Auto transformer supply tends to become a standard on densely traficated lines in USA

(e.g. AT-systems +11/-22 kV – 25 Hz)

1915 The Iron Ore line Kiruna-Narvik

was electrified (15 kV – 15 Hz with

80 kV supply)

New Haven-system 11/22 kV–25 Hz

CG1- loco at 4.600 kW

New York 1934


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Increased demands for power necessitates new solutions for

train power systems

AT system ”reinvented”

1972 Japan, Sanyo Shinkansen

(25/25 kV – 60 Hz)

1981 France, TGV Paris-Lyon

(25/25 kV – 50 Hz)(25/25 kV – 50 Hz)

1987 Hungary, simplified AT system

(25/25 kV – 50 Hz)

1995 Sweden, Kiruna – Svappavaara

(15/15 kV – 16,7 Hz)

Suitable for busy conventional railways, heavy haul and high speed lines.

Substations are expensive and technical complicated installations.


5

Operation for Auto Transformer

Principle of operation for an Auto Transformer

250 A

500 Ae1+e2 e2

Ampere winding balance: I1• N1 = I2 • N2 (”the ideal transformer”)Power for autotransformator: SAT = U1 • I1 = U2 • I2Common winding = reduced weight, smaller volume, reduced losses

Lower price compared to normal two winding transformer.

Option for low leak reactance, particularly important in a train power system

Draw back – no galvanic separation (easier "path" for short circuit currents)


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Terminology for AT systems

Normally used terms:

� Auto transformer only has one coil with three terminations

� Primary and secondary side have no galvanic separation *)

� ”Plus conductor” is connected to contact wire and positive feeder (PL)

� ”Minus conductor” is only connected to negative feeder (NL)

� Midpoint termination – ideally 0 V – is connected to track / return circuit

� Angel between ”plus” and ”minus” conductors is 180°

� Normal designations are 2x25 kV or +25/-25 kV

*) Power supply (transformer) from the high voltage grid, e.g. 220 kV,

will normally be galvanic separated from the train power system.


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AC supply system

Direct supply running rail (RR) or

Direct supply with return conductor (RC)

Return conductorRC


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AC supply systems

Booster transformer with return conductor (BT-RC)


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AC supply systems

Auto transformer with full range voltage supply (AT-2U)

Train power transformer with two secondary coils


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AC supply systems

Auto transformer with contact wire voltage supply (AT-1U)

Train power transformer equipped with one secondary coil

Some times named ”AT-Light”


11

AC supply systems

Earth currents with direct supply (RR)

Earth currents with direct supply

with return conductor (RC)


12

AC supply systemsEarth currents with BT system

Earth currents with AT system


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AC supply systems

Why choose a complicated AT system?

Source:Comparison of BT and ATsystem, EMC-symposium York 1-2. July 2004.Prof. György Varju, Budapest University

Because supply

conditions will

improve

significantly!

Budapest University


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AC supply systems

Why choose a complicated system?

Inductance in an overhead line AC

system is heavily dependent on the

geometric design CL (+25 kV)

PL (+25 kV) NL (-25 kV)

Reduced EMC impact on the surroundings

and reduced stray currents with balanced

impedances in PL and FL (reduced "leakage"

of currents)

geometric design

Inductance can be reduced by a

symmetric configuration and small

distances between conductors

CL (+25 kV)

RR (0 kV)


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AC supply systems

Why choose a complicated system?

Principle of supply (normal operation)

Relative impedance

Acceptabel distance single track

Booster transformer (BT-RC) 100 % 20-30 km

Possible increased distance between substations

Significantly improved quality of voltage

Reduced losses

Better utilization of brake energy

Direct (RR-RC) ~ 65 % 30-40 km

Direct with supply feeder (RR-RC-FL) ~ 60 % 35-45 km

Auto transformer (AT) ~ 20-25 % 60-80 km


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AT system at HSL-railway

French AT transformer 225 kV /2x27,5 kVNominal power 72 MVA (36-36 MVA) SNCF TGV


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AT system at HSL-railway

Electric layout for AT supplySupply station, feeder cables, substation


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AT system in Sweden

Supply system with distributed auto transformers (”AT-Light”)

Source:

BVS 1543.11601 KraftförsörjningsanläggningarAutotransformatorsystem – systembeskrivning,


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AT system in Sweden

Supply system with distributed auto transformators (”AT-Light”)

Banverket AT system 2 x 15 kVAT-transformers 5 MVAUsed at Vännas – Umeå line


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AT system in Sweden



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AT system in Norway


15 kV samleskinne

returstrøm samleskinne

Omformerstasjon

1o km 1o km 1o km

Negativledning – NL -15 kV

Kontaktledning KL + 15 kV

Positivledning PL + 15 kV


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AT system in Norway


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AT system in Norway


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Advantages / drawbacks AT-system

AT system compared to BT system

+ Very low voltage drop in overhead catenery system.+ Reduced losses in overhead catenary system = saved energy! + Auto Transformer every 10th km compared to Booster Transformer every 3rd km.+ Possible longer distance between substations.

- More conductors mounted in overhead catenary system.- More complicated switching equipment in train power system- Risk of locally higher earth current caused by higher power levels.

BT system employed on lines with parallel signaling and telecommunication cables in order to avoid electromagnetic disturbances. AT system can offers the same advantages.

AT system is widely used on high speed lines and railways with heavy freight traffic.AT system can be used on long single track lines to reduce numbers of substations.


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AT system interestingin Denmark?

Electrification 2011

Existing network too expensive to rebuild.

Cost for Kystbanen estimated at 120 mio.kr!

Lines to be electrified in the future could prove interesting.


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AT system interestingin Denmark?

Electrification till 2020

Lunderskov-Esbjerg

København - Ringsted

Ringsted – Rødby/FemernRingsted – Rødby/Femern

Note: Yellow substations not yet decided!


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AT-system interestingin Danmark?

Probable development

after 2020

The rest of Sealand 2018-2022

Main lines in Jutland 2020-2025

Other local lines 2025-2035


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Thank you for your attention!Electric railway at Skærum Teglværk 1909

Electric railway at Ørestad 2012

Questions?

autotransformer system

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