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BRINCKERHOFFPARSONS
BRINCKERPARSONS
EMC Seminar17 November 2007
EMC Seminar17 November 2007
Harmonic Distortion Assessment
of a DC Railway Traction Power System
Harmonic Distortion Assessment
of a DC Railway Traction Power System
IEEE Hong Kong SectionEMC Chapter
IEEE Hong Kong SectionEMC Chapter
BRINCKERHOFFPARSONS
ContentContent
Introduction
Objective
Modelling of the System
Methodology
Summary of Findings
Conclusion
BRINCKERPARSONS
IntroductionIntroduction
Harmonics generated by multiple-pulse rectifiers arewell known EMI disturbance to trackside equipment in adc traction railway environment.
The magnitude and frequency of harmonic currents canvary with many factors that may cause an impact on thefunctions of safety critical electronic equipment such asthe signaling system.
This paper describes a case study in which a model of dctraction power supply and traction current return circuit
has been used for assessing the effect of dc harmonics onthe signaling system in a quantitative manner.
BRINCKERHOFFPARSONS
ObjectiveObjective
The objective of this exercise is to verify that the dcharmonics generated by the 1500 V dc traction powersupply will not cause any troubles to the normaloperation of signaling equipment. Mitigation measureswill be proposed if any risk of disturbance is identified.
Source of EMI is the transformer-rectifier unit intraction substations generating harmonics under normaland abnormal conditions
Victims susceptible to the EMI include audio frequencycoded track circuits and radiating cable loops andbeacons installed on the track.
BRINCKERPARSONS
Modelling of the SystemModelling of the System
The System includes the 24-pulse Rectifiers in TractionSubstations (TSS), Electric Multiple Unit Trains (EMU),Overhead Line System (OHL) and Rails with tractionreturn bonding cables.
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MethodologyMethodology
Step 1: Determine Harmonic Voltage SpectraHarmonic voltages based on 12-pulse transformer rectifierunits were investigated taking into consideration a numberof equipment failure and imperfections scenarios
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MethodologyMethodology
Step 1: Determine Harmonic Voltage Spectra
FFT
FFT
Diode Arm broken
BRINCKERHOFFPARSONS
MethodologyMethodology
Step 2: Estimate Harmonic Currents Flowing Throughan EMU and the Aggregate Effect of Several EMU
Simplified Model of
TSS and Single EMU
VH1 Z
EMU1
IH1
VH Z
EMU1
ZOHLx
ZRAILx
ZEMUx
IH1
IHx
Circuit for Weighting
Factor Estimation
One-sided ApproximationCurrent Divider Approximation
Multiplier on Single Train
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MethodologyMethodology
Step 2: Estimate Harmonic Currents Flowing Throughan EMU and the Aggregate Effect of Several EMU
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MethodologyMethodology
Step 3: Harmonic Current Flowing in Return Rails
S Bond between EMU and TBB TBB between EMU and S Bond
TBB
I3
I4
Axle "S" Bond
D1
D2
TBB
I1
I2
Axle "S" Bond
D2
D1
Unbalanced Current flowing through
the Track Circuit as a function of
train position
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Step 3: Harmonic Current Flowing in Return RailsThe immunity levels of various trackside signaling equipmentare defined as the maximum permissible in-band harmoniccurrents flowing in the rails
MethodologyMethodology
Check for In-band EMI levels to
determine severity of disturbance
f1 f2fH
S
f1 f2fH f1 f2
IHZT
FHZ
V
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MethodologyMethodology
d.c. Harmonic - Train LC Filter Parameter Variation
103
104
105
0
500
1000
1500
(VARYING INDUCTANCEL1AND FIXEDCAPACITANCEC1)
Frequency(Hz)
Tra
inImpedance(Ohm)
FTG-S
CVCM
CT BeaconRC 2L1
L1
0.5L1
0.1L1
0.01L1
Train Impedance Against Frequencywith Varying Inductance
(1 kHz 200 kHz)
Train Impedance Against Frequencywith Varying Inductance
(1 kHz 20 kHz)
103
104
0
50
100
150(VARYINGINDUCTANCE L1 ANDFIXEDCAPACITANCE C1)
Frequency (Hz)
Tra
inImpedance(Ohm)
FTG-S
CVCM
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MethodologyMethodology
d.c. Harmonic - Train LC Filter Parameter Variation
Range of C1: variation between 0.01 C1 to 10 C1
Train Impedance Against Frequencywith Varying Capacitance
(1 kHz 200 kHz)
103
104
105
0
200
400
600
800
1000
1200(VARYINGCAPACITANCE C1AND FIXEDINDUCTANCE L1)
Frequency (Hz)
Tra
inImpedance(Ohm)
BRINCKERHOFFPARSONS
Summary of FindingsSummary of Findings
Track circuits were identified as the most vulnerabletype of signaling equipment under influence of harmoniccurrents.
The estimated harmonic currents within the 3dBbandwidth of the signaling equipment were comparedwith the corresponding maximum permissible currentlimits.
It is possible that the harmonic currents at two of theTrack Circuit operating frequencies will likely exceed thepermissible limits.
Other harmonics generated by the traction power supplyequipment in the interested frequency ranges are withinlimits with a quite generous safety margin.
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ConclusionConclusion
Different in-feed supply conditions, power supplyequipment failure and imperfections scenarios have beenassessed in this exercise.
Generally speaking, the estimated amount of harmonicsso generated will not exceed the limits as specified by thesignaling contractor except in a few specific conditions.
Based on the HDA findings, the EMC design and testspecifications for rolling stock and signaling system canbe developed and assessed.
BRINCKERHOFFPARSONS
Thank YouThank You