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Railway, Metro and Lightrail
Electrification –Return Circuit
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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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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
Peter L. Ottosen
Specialist
Thank you!