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ELECTRIFICATION – RETURN CIRCUIT1

Railway, Metro and Lightrail

Electrification –Return Circuit

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ELECTRIFICATION – RETURN CIRCUIT2

COWI today

2015 net turnover: DKKm 5,577

Approx. 6,400employees

World-class competencies within

engineering, economics and environmental

science

85 years of history

At any given time, 13,000 ongoing

projects

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World-class competencies and cross-border collaboration

› COWI is organised in four business lines ‒ Denmark, Norway, Sweden and Bridge, Tunnel and Marine Structures (BTM).

Business line

SWEDEN

Business line BTM

Business line

NORWAY

Business line

DENMARK

Why Electrify the railway?

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› Nørreport station Monday morning in a very polluted atmosphere due to diesel trains -> solution electric trains

› Ålborg airport a Tuesday morning – the plane is cancelled due to fog -> solution electrification as more efficient system than diesel

› Copenhagen Hamborg in 2 hours and 46 minutes from centre to centre -> electrification

› Reduction of CO₂ -> Electrification

› Efficient use of wind energy -> Electrification

› Urbanisation – Stop getting bad lungs -> Electrification

› Goods on rail in a clean manner -> Electrification

› Diesel train are harder and more expensive to buy as less are made due to more demand for electrical trains

› and many more good reasons

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Urbanization results in many electrical systems that

might interact wrongly

Since 2013 more people lives in cities than in the countryside world wide – this will NEVER change back

Agenda

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› Electrification systems (slide 7-11)

› Earthing and bonding – E&B (slide 12-20)

› Stray currents (Slide 21-24)

› Protection (Slide 25-32)

› Electromagnetic interference – EMI (Slide 33-34)

› Immunization (Slide 35 – 46)

› Return circuit modelling (Slide 47 – 55)

FAR TOO MANY SLIDES -> I will jump in the slides so it fit with the half an hour–Sorry about that

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Electrification Principle -What are the differences in generations?

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Electrification Principle– Generation AReturn circuit via running rails

Stray Currents

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Electrification Principle– Generation BReturn circuit via running rails and return conductor

Stray Currents

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Electrification Principle– Generation CBooster transformer system

Stray Currents

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Electrification Principle– Generation DAuto-transformer system (AT)

Stray Currents

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Why AT system is smart?

Exploiting circular currents at section with train and lower currents from substation to train.

Lower interference with adjacent lines due to low currents and feed from two AT's

400 A to train

200 A delivered

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Earthing and bonding

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Principle - Return circuit and E&B of DC traction systems

Strive to have an isolatedreturn system – "nothing is

connected to rail"

Principle - Return circuit and E&B of AC traction systems

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Strive to have an open returnsystem – "everything is

connected to rail"

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Earthing and bonding on stations – DC railway

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Earthing and bonding of structures – AC railway

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E&B of level crossing – DC railway

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Example of E&B system – VLD not shown

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Why E&B of DC light rail is sometimes connected to E&B for AC heavy rail? Danger to humans

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Stray currents

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DC train systems where return current runs in unplanned path's due to lower impedance than return conductor and return rail.

Corrosion of parallel pipes, reinforcement in tunnels etc.

...or caused by malfunctioning

cathodic protection, high

voltage DC, welding, and

other electrical driven

mechanisms.

2e-+ 2H2O H2 + 2OH

-

Stray currents corrosion principle

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Steel

Cathode 4e-+ 2H2O + O2 4OH

-

Anode

Fe2+ + 2e-

Fe

iCorrosion

VOLTAGE GRADIENT

x Volts y Volts

Incomingcurrent

OUTGOINGCURRENT

i

2Cl-

2e-+ Cl2

4OH-

4e-+ 2H2O + O2

Fe 2e-+ Fe2+

Stray current - example

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Corrosion wherecurrent leaves pipe

Stray current - example

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Using E&B to protect sensitive structures against straycurrent driven corrosion?

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Using E&B to protect sensitive structures against straycurrent driven corrosion?

Using Cathodic protection to protect against straycurrent – basic principle

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rein

forc

em

ent

concrete

Cl-

Cl-

Cl-

Cl-

refe

ren

ce

ele

ctr

od

e

e-

e-

e-

e-

mV

Cl-

Cl-

anode

e-e-e-

e-

+

Cathodic protection – basic principle

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Pourbaix diagram for iron in water solution (25oC, 1 atm)

Primary effect of cathodicprotection:Change of potential to more negative values

pH

PITTINGCORROSION

PASSIVE

IMMUNE

Pote

ntiale

, V

CORROSION

water separation

2H2O + 2e- H2 + 2OH-

hydrogen development

Cathodic protection - History

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1824 20151900 1973 1987 2003

Sir Humphrey Davy discovers cathodic protectionwith sacrificialanode. The method is used for protection of subsea metal parts on ships.

The method is spread to pipelines in soild. As the electrical impedancein soil is too highthe methoddevelops to chatodicprotection with added current.

Richard Stratfulluses the method for reinfoced concretconstructions. He uses silicium metal anodes covered with a layer of conductiveasphalt.

The firstinstallations in Denmark.

The Vejdirektoratet accepts cathodicprotection as a repair and operations method.

Cathodic protectionof reinforcedconcreteconstrcution is common practise.

Today we have more than 25 years experience with cathodic protection in Denmark.

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Cathodic protection - background

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3

1

5

rein

forc

em

ent

co

ncre

te

6

2

7

3

3 +4

transformer/inverter

board

1. Reinforcement steel

2. Anode system

3. Cabels

4. Transformer/inverter

5. Reference electrode

6. Control system and datalogger

7. Remote control

Catodic protection is an electric repairmethod, where corrosion of the reinforcement steel is stopped by adding an electric current between the reinforcementand an anode system via a transformer/inverter connected to public supply.

Cathodic protetction as a repair strategy

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Initialization Propagation

CO2, Cl-

Time

Expected life/time to repair Increase of lifetime

Accept

Lífe time for cathodic protection

1 2

3

EMI – Electromagnetic interference

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Victims can be:- People living i houses nearby- Hospitals (sensitive equipment)- Laboratory equipment- Dentists and specialist doctors

EMI – Electromagnetic interference

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Immunization of systems along the track

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Example of study:Will immunisation of Banedanmarksignalling equipmentbe necessary due to establishment of Århus lightrail?

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Stray Currents and immunization study usingsimulation – ABACUS tool

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Two trains accelarating

Stray Currents / Immunisation – Electrical properties of soil

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Soil resistivity

Stray Currents / Immunisation

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FE model

Stray Currents / Immunisation

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FE model

Stray Currents / Immunisation

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Two VLD open – local isolation fault

Stray Currents / Immunisation

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Two VLD open – local isolation fault

Stray Currents / Immunisation

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Two VLD open – local isolation fault

+ 2.94e +01+ 5.00e +00+ 4.58e +00+ 4.17e +00+ 3.75e +00+ 3.33e +00+ 2.92e +00+ 2.50e +00+ 2.08e +00+ 1.67e +00+ 1.25e +00+ 8.33e -01+ 4.17e -01+ 0.00e +00- 1.06e -01

Stray Currents / Immunisation

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Two VLD open – local isolation fault

Stray Currents / Immunisation

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Overall result

Stray Currents / Immunisation

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OPERATIONAL SITUATION PMAX DPMAX DPMAX

500

DPMAX

1000

1 Two VLD open (normal

operation)

1,4 V 0,26 V 1,1 V 1,3 V

2 Aarhus VLD closed 1,2 V 0,2 V 0,9 V 1,2 V

3 Two VLD closed, local

isolation fault

2,9 V 0,74 V 2,54 V 2,82 V

4 Aarhus VLD closed,

local isolation fault

2,5 V 0,6 V 2,2 V 2,5 V

5 Two VLD open rail

conductivity 600 S/km

0,1 V 0,2 V 0,2 V 0,2 V

6 Aarhus VLD closed, rail

conductivity 600 S/km

0,9 V 0,1 V 0,2 V 0,2 V

WORST CASE –

classical track joint based

signalling will malfunction

around 1 V and higher.

I.e. immunisation

is necessary.

Overall result

Modelling used for return circuit issues – OPN tool

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Establishing the model

Slice modelling including EMI coupling effects

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Sequence of slides

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Magnetic flux densityExample using OPN

Maximum return cable current

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0

200

400

600

800

1000

1200

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

SP WU dir.

ATS WU dir.

ATS GUA dir.

SP GUA dir.

MAX.

CU

RREN

T [

A]

SECTION NO.

Short circuit current study

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0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

1961 1971 1981 1991 2001 2011

ISOLATOR AT INFEED SHORT CIRCUIT CURRENT

SHORT CIRCUIT POSITION (KM)

MAX.

CU

RREN

T [

A]

Maximum rail earth potential study

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ELECTRIFICATION – RETURN CIRCUIT54

0

20

40

60

80

100

120

140

160

180

1961 1971 1981 1991 2001 2011

ISOLATOR

LR U LEBC Up

RR U LEBC Up 2

AT

LR U LEBC Up 2

RR U LEBC Up 3

Infeed

LR U LEBC Up 3

URE max

RR U LEBC Up

VO

LTAG

E [

V]

POSITION (KM)

78 V

Example of simulation of AT system

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Allan Kjaer

Technical Director

apkj@cowi.com

Peter L. Ottosen

Specialist

plot@cowi.com

Thank you!