comparison booster transformer

EMC York 2004July 1 & 2, 2004

Prof. György Varjue-mail: [email protected]

Budapest University of Technology & Economics

Comparison of the booster transformer and auto transformer railway feeding systems,

Feeding features and induction to telecom lines

2

Presentation items:

1. Railway feeding voltages and recent alterations of the feeding systems in Europe

2. Qualitative analyses of the ac. feeding systems

3. Modeling and parameters of railway feeding systems

4. Systems comparison

5. Conclusions

3

1. Railway feeding voltages and recent alterations of the feeding systems in Europe

4Feeding voltages

in Europe

3000 V dc.1500 V dc.50 Hz 25 kV ac.16 2/3 Hz 16 kV ac.

5

Recent alterations in feeding systems

• dc. feeding replaced by ac. 50 Hz, 25kV or 2x25 kV– for high speed train (e.g. TGV)– for high density traffic (e.g. Netherlands)

• BT system replaced by AT– for heavy freight train traffic (e.g. Sweden

iron ore transport) – for high speed train

6

2. Qualitative analyses of the ac. feeding systems

7

Feeding systems of ac. supply

Simple feeding with rail (+ earth) return: RR

Booster transformer with rail return: BTRR

Booster transformer with return conductor: BTRC

Auto transformer: AT

Combined systems: AT/BTRR

AT/BTRC; ATPF/BTRC; ATPF/SCBT

8Simple feeding with rail (+ earth) return:

RR system

9Simple feeding with rail (+ earth) return: RR system

Quantities characterizing the current portion & profiles

Series impedance of the return rail(s)-to-earth loop, as per unit length values:

o ZRR, series impedance of the return rail(s)-to-earth loop,

o ZCR, mutual impedance between the contact line system and return rail system with common earth return,

o GRR the rail-to-earth leakage conductance,

10Simple feeding with rail (+ earth) return:

RR systemQuantities characterizing the current portion & profiles

Derived quantities: • rail current portion and screening factor behind the end/effect zones:

Rail current portion: Screening factor

RR

CR

ZZq −=

RR

CR

ZZqk −=+= 11

• length constant of the rail-earth circuit with the approximation, that ωLRR >> RRR:

RRRRGLωατ 21 ≈=


Rail current and point screening factorat 50 Hz supply


Rail current and point screening factorat 16 2/3 Hz supply

13

Booster transformer system with rail return: BTRR system

14Booster transformer system with return conductor:

BTRC system

15

Booster transformer system with return conductor: BTRC system

16

Continuity of the current return path BTRC system

17Auto transformer system

AT (with 2U power source)

18Auto transformer system :

AT (with 1U power source)


with increased NF voltageAT [16/25 kV]


with increased PF and NF voltages:ATPF [16/2x25 kV]

21Combined feeding system

AT / BTRR


AT / BTRC

23Combined feeding systemATPF / BTRC


ATPF and shunt connected BTATPF / SCBT

25

3. Modeling and parameters of railway feeding systems

• Multiconductor line representation

• Representation by two phase sequence networks

26

Multiconductor line representation of railway feeding (AT) system

27Two phase sequence network representation

BTRC system

Zm ZmZm

28Two phase sequence network representation

AT system

Ztm Ztm Ztm

29Two phase symmetrical componentsbasic voltage & current expressions

Phase quantities Symmetrical components:

U U UC = +0 1 ( )PC UUU +=21

0 Voltages:

10 UUU P −= U U UC P112

= −( )

Note: UCP = 2U1

10 IIIC += ( )PC III +=21

0

Currents

10 IIIP −= ( )PC III −=21

1

Notes: current in the balanced loop: IC = -IP = I1

current in the return path (rail+earth): Ireturn = IC + IP = 2 I0

30Two phase symmetrical component representation of two coupled lops

Coupled loop circuit Equivalent of the coupled loop

Positive sequence loop Zero sequence loop

CPself ZZZ −=0 CPself ZZZ +=0

( )PPCCself ZZZ +=21

31Representation of the network elements

Line configuration (Rsi – Svv line)


Multiconductor line parametersDistributed series and shunt elements

of the railway line model

Ic(x) ZCC

IR(x) ZRR

IP(x) ZPP

ZCR

ZRP

C

R

P

ZCP

UP(x)

UR(x)

UC(x)

R

C P

CP0

CCP

CCR CRP

CC0GR0 CR0


Line system

Multi-conductor network Sequence networks

positive sequence

zero sequence


Power supply (converter or transformer station)



Traction unit (engine, motor coach)Multi-conductor network Sequence networks

36View of auto & booster transformers

(Installed at the Kiruna – Råtsi – Svappavaara line in Sweden)

37

Representation of the network elementsBooster transformer: detailed circuit diagram


Booster transformer: magnetizing impedance


Booster transformer: simplified circuit diagram


Zm


Bond (between RC and RR)



Auto transformer: magnetizing impedance neglected


42

S tudy item s: a) Equivalent im pedance, voltage stability b) System losses c) Power rating of auto transform ers d) Induction effect:

o Inducing earth current profiles o Length-current integrals o Induced longitudina l em f

e) Rail-to-earth potentia l f) Rail-to-ra il potentia l

4. Systems comparison

43

a) Equivalent impedance, voltage stability

44Equivalent impedance

vs. train position (spacing 6 km)

BTRR BTRC

45

Equivalent impedance vs. train positionAT system (spacing 12 km)

46Comparison of impedances vs. train pos.

for BTRC & AT systems

47Equivalent impedance vs. train position

AT systems

48Comparison of voltage drop for AT and BT systems

(Traction power 8 MVA)

49Comparison of normalized values of

the equivalent impedances forBTRR, BRRC & AT systems

50Voltage drop, versus train location

for different AT supply options

2U

3U

0

2

4

6

8

10

12

14

16

0 5 10 15 20 25 30 35 40train position, km

∆U[%]

5AT4AT3AT

Train load: 10 MW, cosϕ = 0.8

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d) Characterization of the induction effect

o Inducing earth current profiles

o Current-length integrals

o Induced longitudinal emf

52

Inducing earth current profilesCases studied for demonstration

53Earth current profiles at different train locationsBTRR system

Spacing: 6 km, G=0.25 S/km, Train current: 500A

54Earth current profiles at different train locationsBTRC system

Spacing: 6 km, G=0.25 S/km, Train current: 500A

55Earth current profiles at different train locations

AT systemSpacing: 12 km, G=0.25 S/km, Train current: 500A

563D surface of the inducing current

BT system

57

3D surface of the inducing current BT system

58

Current-length integralsCalculation principle of the current-length integral

59

Maximum of the the current-length integralAT system

Integration window: 6 km Integration window: 42 km

60Maximum of the normalized current-length integrals,

base the current-length integral of the BT systemAT system

61Current-length integrals for different

feeding systemsParameter: rail-to earth leakage, G

62Average inducing current for different

feeding systemsParameter: rail-to earth leakage, G

63

Induced longitudinal emf

64Map of the measured line(Kiruna – Råtsi – Svappavaara)

65

C - R short circuit locations, for 16 2/3 Hz measurements

BT system

66C - R short circuit locations,for 16 2/3 Hz measurements

AT system

67

Longitudinal voltage measurementsSections of telecommunication cable

68Induced longitudinal voltage vs. train location

in total cable sectionAT system

0

20

40

60

80

100

120

1.32

9

4.31

4

7.12

8

10.3

30

12.2

22

15.1

74

17.4

23

20.4

12

22.5

72

25.4

90

28.8

10

32.4

24

36.5

00

km

V

calculated G=0.5 S/km

calculated G=0.24 w S/km

measured

69Induced longitudinal voltage vs. train location

Comparison of BT and AT systemsMeasured cable sections: total

0

20

40

60

80

100

120

1.32

9

2.63

1

5.78

8

7.12

9

10.1

8

11.2

82

12.2

23

15.1

74

17.4

23

19.2

32

21.4

92

23.8

24

25.4

90

28.8

10

30.3

35

34.3

08

36.6

00

k

V AT

BT

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e) Rail-to-earth potential

71Real-to-earth voltage profile vs. length

BTRR systemTrain at 9.01 km

(BT location)Train at 41.99 km

(at the middle of BT spacing)

72

Maximum rail-to-earth voltages vs. train positionBTRR system, spacing 6 km

73Real-to-earth voltage profile vs. length

BTRC systemTrain at 2.99 km

(BT location)Train at 39.01 km

(at the middle of BT spacing)

74

Maximum rail-to-earth voltages vs. train positionBTRC system, spacing 6 km

75

Real-to-earth voltage profile vs. lengthAT system

Train at 17.90 km(middle of an AT spacing)

Train at 24.01 km(AT location)

76

Maximum rail-to-earth voltages vs. train positionAT system, spacing 12 km

77Maximum rail-to-earth voltages for

different feeding systems

BT spacing 3 km BT spacing 6 km

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Conclusions

The results of simulation calculations and site experiences

a) The equivalent impedance is significantly (about 3 times) less for the AT

system than that for the BT system. b) Induction to telecommunication lines:

• the BT and AT systems are, practically, identical. • the maximum longitudinal voltage occurred in the whole line length

with the current injection at the Svv end • the induction effect could significantly be reduced by the improvement

of the balance ◊ for BT system balancing the mutual impedances of the catenery

system and the return conductor to rail ◊ for AT system balancing the self impedances of the catenery system

and the inverted feeder

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Conclusionscont.

c) The rail potentials in personnel safety point of view, they are also similar in AT and BT supply systems with the following remark:

• in case of AT supply the rail-to-earth voltage can reach higher value in the relatively big AT spacing

• in case of BT supply, the voltages over insulated joints are higher in certain places.

d) Both the induction effect and the rail potential are significantly affected by: • spacing of BT or AT • rail-to-earth leakage conductance, G

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Conclusionscont.

Proposals for further study

(1) The feasibility of the use of positive feeder.

(2) The feasibility of the combined feeding systems.

(3) Methods for balancing the AT feeding by: • optimised negative feeder arrangement • use of current unbalance suppression unit (CUS).

81

Thank you for your attention

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comparison booster transformer

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