My 'info'-presentation on my research on pantograph failures. This part of the presentation should cover more advanced concepts of pantographs, its precautions in use and regime of failures. Understanding fundamental concepts on its failure causes & mechanisms, the presentation explores the ways that pantographs can be monitored against, to deter preventable defects from propagating.

1. 19/10/2015 1
Kelvin Lam
Analysis on Pantographs -
Pantograph Safety
Summer 2015

2. Safety of Pantographs
& Pantograph Failures
19/10/2015 2

3. Safety first!
19/10/2015 3
High voltage system poses an imperative
safety concern.

4. Safety first!
19/10/2015 4
• From previous slides
we understood how
associated systems
would be affected if
pantograph fails.
• We appreciate how
safety and fatigues
form an integral part of
consideration when
designing a pantograph
system.

5. Safety Feature of Pantographs
• As with any transportation industry, safety of
passengers, workers and the surroundings are
paramount.
• Protection to assets are also deemed crucial.
• The cycle of confidence & trust amongst
railwaymen would help promote safety standards
within railway.
(Maslow’s Law of Motivation)
19/10/2015 5

6. Maslow Law of Hierarchy of Needs
19/10/2015 6
Leads
to…
When
achieved
, then…

7. Protection to
assets
Integrity of system
maintained
Full (intended)
protection to
human lives
Staff morale
Customer
satisfaction
19/10/2015 7

8. Criteria in consideration
• RAMS
• R eliability - its ability to perform a
specific function.
• A vailability - the ability for a said
system to keep
performing its intended
function.
• M aintainability - ease to be repaired &
maintained.
• S afety - its requirement that within
its life cycle, no
human/environment/assets
are jeopardised.
19/10/2015 8

9. Carbon Strip Defect
• Carbon strips on pantograph are the physical contact
interface between OHLE and the rolling stock.
• High speed vibrations/resonance of the OHLE, arcing due to
humidity & loose contacts and thermal issue are main cause
to carbon strip damage.
• Carbon graphite is a dry lubricant, and gradually wears out.
19/10/2015 9

10. Fatigue Regime
• Regime 1
• First consider graphite…
Carbon atoms are arranged in a hexagonal form; this is due
to its absence of pi-electrons in the 2nd energy level.
• Electrons are covalently shared – forming a strong, rigid
bond.
• There are 4 ‘vacancies’ at the pi-bond, but due to dimension
only 3 are bonded. This leaves one space to complete the
bond.
• The 4th electron is delocalised over the entire structure; they
are not associated with any atoms.
• This forms interplanar bonds; long hence weak.
19/10/2015 10

11. 19/10/2015 11

12. Fatigue Regime
• As residual shearing stress increase in the lattice…
• The interplanar bonds are damaged first.
• The planes slide upon others, and eventually become dissociated
with the lattice.
• Gradual, planar removal of carbon means the carbon contact strip
becomes worn out.
• Solution:
Introduce other materials, i.e. copper.
Carbon strip = 85% Carbon + 15% Copper.
19/10/2015 12

13. Fatigue Regime
• Regime 2
• When there presents a poor electrical contact, electric current
would ionise air particles, causing an electric arc.
• Temperature of an electric arc can reach 19273K (19000C)
and able to vapourise metals and, of course carbon.
• Arc/flashover damages cause dents on the strip, increasing
co-efficient of friction.
• Increasing asperities would increase surface area for
shearing stress, and of course, increased rate of degradation.
19/10/2015 13

14. Fatigue Regime
• Increased surface area also
attract oxidation process.
• A SEM spectrum of a used
carbon strips show that strip
contained 1% sulphur and
oxygen.
• Different particles would change
regime of dislocations, making
faults harder to detect.
19/10/2015 14
Impurities

15. Fatigue Regime
• Regime 3
• As the carbon strips transverse a longer distance, impurities
are caught in layer in between carbon strip and the aluminium
layer.
• The layer is composed of an epoxy adhesive with oxygen, a
poor conductor.
• Thermal energy generated with heat.
• Residual stresses caused by expansion further cause
crystalline defects.
19/10/2015 15
Dislocations from
thermal expansion can
cause slip planes.

16. Safety Feature of Pantograph
• Auto-Drop Device (ADD)
A device that automatically lowers a pantograph when an
abnormality is detected.
• The objective is to minimise the risk of severing the damage
to the OHLE and the pantograph system.
• It does not prevent damage but rather an effective solution to
prevent further damages.
• Two types
 Pneumatic
 Mechanical
19/10/2015 16

17. Auto-Drop Device
• Pneumatic
• Pantographs are pushed up and
sustained using air pressure from
cylinder.
• Gas tube placed within the carbon
strip. When the strip becomes wear to
an extent, it destroys the silicon tube
and pantograph loses air pressure.
• Pantograph drops.
19/10/2015 17

18. Auto-Drop Device
• Pneumatic ADD prevents permanent
damage to pantograph from the lack
of lubricating substances.
• However it does not deter damages
caused by abnormal loads and
defective wires.
19/10/2015 18

19. Auto-Drop Device
• Mechanical
• Unintended vibrations do not immediately wear pantographs
so another device is designed to deter such kind of damage.
19/10/2015 19

20. Auto-Drop Device
19/10/2015 20

21. Auto-Drop Device
• In normal running operations, the longitudinal forces will be
transmitted to two welded piece which is restrained by a
shear pin.
• When abnormal longitudinal forces are observed, due to
excessively shear stress the pin will deform and break apart
first.
• The two welded piece can then move freely, giving many
degrees of freedom to the collector head.
• The movements in any degrees of freedom will tension the
Bowden cable, and in turn releasing a latch.
• The latch no longer locks the coupling rod so the connection
is interrupted.
• Pantograph lowers gradually.
19/10/2015 21

22. Harmonics & Vibrations
• Vibrations refer to the
oscillation of an object
about equilibrium point.
• Vibrations on wire
influence greatly on
pantographs, given that
the two form a coupled
system.
• The cause of vibrations
in pantograph can be
explained below;
19/10/2015 22

23. Harmonics & Vibrations
1. Vibrating response due to irregularities on
track
2. Resonance on car-body
3. Damping effect on actuators and springs
4. Frictional effect between carbon strip and
OHLE
5. Self-excitation due to harmonic frequencies
on wire
19/10/2015 23

24. Vibrating Response
Vibrating response due to irregularities
on track
Resonance on car-body
• Vibrations from track are caused by
irregularities present on railhead (track)
or poor ground conditions.
• Despite not directly related to
pantographs, these trainborne vibration
causes pantograph to move vertically at
random.
19/10/2015 24

25. Vibrating Response
• When train travel at higher speed, the
time tranversing irregularities would be
shortened, as per expressed in the
below expression:
• …where lambda refers to the
distance-span of an irregularity (surface
roughness) and other symbol has its
usual meanings.
• Using Planck’s constant, we know
higher frequencies = higher energy.
19/10/2015 25

26. Vibrating Response
• We cannot ignore low frequency
vibrations as pantograph offers a
pivotal effort.
• And using FEM modal analysis:
(source: Krell Engineering)
• The FEM analysis is based on an
‘eigensystem’ where we consider
stresses due to vibration in principle
tensor for resonance.
• Another method refers to the use of
Fourier analysis.
19/10/2015 26
Low frequency Travelling
along distance
without
restraining
Pivotal effort
(due to
mechanical
advantage)
Vibration is
amplified

27. Vibrating Response
• It is evident that pantographs, as
a large structure, can incur
‘many forms’ of modal
vibrations.
• Suitable strucutral
reinforcements required
throughout parts with ‘excessive’
stress in order to increase its
modal/natural frequencies.
• Reinforcements shall not be
done excessively – the ‘beam’
will incur more weight, hence
enhancing internal shearing
stress.
• Failure to do so will incur
increased fatigues and failures –
reduction in revenue!
19/10/2015 27

28. Damping effect on actuators and springs
• The higher frequency vibrations incur energies and are
sometimes stored by dampers.
• Pantograph itself is a viscous model (discussed later) and
therefore such energies are dissipated slowly and gradually.
19/10/2015 28
Rather than
dissipating all
stored energies at
once (with
extreme high
amplitude) the
system is heavily
damped hence
prolonged
vibration protects
the system.

29. Damping effect on actuators and springs
• Viscous agents include compressed air in air cylinders.
Air is a fluid and are compressible and shaped to any form – this
property can be exploited in this case.
• Other examples include springs on pantographs, and to an
extent, elastic deformation along the pantograph structure.
• Hence the total energy stored by overall damping factors;
19/10/2015 29

30. Frictional effect between carbon strip
and OHLE
• Friction refers to the resistive effort opposed to a moving object.
• The cause of friction is complex and is a study of tribology.
19/10/2015 30
Study of tribology. Source: tribocoating & University of
Leeds

31. Frictional effect between carbon strip
and OHLE
• Some possible causes of
pantograph friction:
Asperities
• As with any materials, there
can be fatigues along the wire
hence causing asperities.
• These fatigues can be caused
by excessive bending and
shearing stress caused by
reaction force.
• Or caused by residual stressed
from manufacturing (i.e.
unequal cooling when
annealed).
19/10/2015 31
Diagram illustrating asperities
as a cause to solid friction.

32. Frictional effect between carbon strip
and OHLE
• Scanning Electron
Microscope (SEM)
showing micro-
asperities present
along a metallic wire.
• Despite tiny (50
nanometres) it is still
observable when
millions of asperities
are physically
contacted as a time.
Source: Lepienski et al.
19/10/2015 32

33. Frictional effect between carbon strip
and OHLE
Rolling Effect
• Rolling friction refers to the
resistance caused by elastic
deformation of the wire.
• When pantograph exerts an
upward force to a wire, the
wire may undergo elastic
deformation.
• Because the centroid of the
wire has changed, we
effectively disrupted the
direction of stress fields, in
response to principle strains.
19/10/2015 33

34. Frictional effect between carbon strip
and OHLE
• In this case, due to the
deflection of centroid
planes;
• Stress are observed in
a different direction.
• If stresses are now
differed compared to
the magnitude of
principle stress, this
means energies are
now located at a
different area.
• As pantograph travel
across different
locations, the mode of
vibration also differs.
19/10/2015 34

35. Frictional effect between carbon strip
and OHLE
• Using tensor
transformation, we
can explain how
stresses have varied
during deformation.
19/10/2015 35

36. Self-excitation due to harmonic frequencies on
wire
• The pictures show effect of conductor galloping.
• This is caused by increased amount of energy transmitted by
wind.
• Dependent on the property of wire, as energy reaches within
the Q-factor (quality factor) bandwidth…
• The damping reduces drastically, causing egregious
vibrations.
19/10/2015 36

37. Self-excitation due to harmonic frequencies on
wire
• Due to presence of natural frequencies in OHLE system, there
can be excited vibrations along the wire.
• Each OHLE wire covers a long distance, hence there are
many degrees of freedom on where modes of vibration might
occur.
• Another cause of self-excited vibration is wind.
(Conductor gallop)
19/10/2015 37

38. Self-excitation due to harmonic frequencies on
wire
• Different catenary types offer various extent of damping,
therefore altering the mode of vibrations.
• The 3 types of catenary:
- Simple
- Compound
- Stitched
19/10/2015 38

39. Self-excitation due to harmonic frequencies on
wire
19/10/2015 39
Simple catenary Simple-stitched
catenary

40. Self-excitation due to harmonic frequencies on
wire
19/10/2015 40
Elastically-stitched
catenary
Compound catenary

41. Self-excitation due to harmonic frequencies on
wire
• Different catenary types offer varying extent of stiffness and
damping, due to the different configurations used.
• Originally, the compound catenary was used in the first
Shinkansen (Tokaido Line) route in Japan. The original
system has excessive vibrations and hinder top speed
permitted.
• To increase speed stiffer system is needed, so the simple-
stitched system was used as there are less damping =
increased modal frequency.
• Stitching enhances the stiffness and vibration criteria of the
catenary system, hence allowing higher speed trains to travel
with increased pneumatic pantograph pressure (greater
electrical contact).
19/10/2015 41

42. Self-excitation due to harmonic frequencies on
wire
• Wire stitching means lower stress load is present along the
wire.
19/10/2015 42

43. Self-excitation due to harmonic frequencies on
wire
• Effects on pantographs:
• Increased stress cycle on the carbon strip
 shortened service life
• Increased load on pantograph structure
 more stringent FEM analysis required
• Varying contact force
 may cause excessive contact force towards OHLE,
causing damage
19/10/2015 43

44. Pantograph Height
• Pantograph cannot be kept at the same height constantly
throughout its revenue service.
• Opportunities that OHLE and pantograph will incur a change
in ‘above top of rail’ distance (ATR).
• Next slide illustrates type nomenclature of railway heights.
19/10/2015 44

45. Pantograph Height
19/10/2015 45

46. Pantograph Height
• Factors:
• Gauge clearance
Some railways were built in
restrictive areas where gauge
becomes tight.
OHLE are gradually ‘lowered’ in
order to maintain suitable
clearance from existing
infrastructures.
19/10/2015 46

47. Pantograph Height
• Heights of the pantograph should be actuated based upon
OHLE height.
• Otherwise, pantograph strike occurs, causing power failure of
the railway.
19/10/2015 47
A Class 377 stopped immediately
after pantograph striked a low
bridge. The OHLE was damaged
and the rear pantograph
automatically lowered after
abnormalities were detected.

48. Pantograph Height
• OHLE Weight
• OHLE are made of copper with a density of 8960 kg/m3.
• If we model the wire as some ‘marching-’dots with weights, it is
inevitable for a wire to drop as moment and longitudinal stress
incurs.
19/10/2015 48

49. Pantograph Height
• Finite Element Method
approach
• The continuum nature (< 1.5
km) of an overhead wire
suggests that non-linear
estimations have to be
employed.
• We discretise the OHL wire
into many tiny ‘marching’-steps
19/10/2015 49
Source: “Influence of static and dynamics on
high performance catenary designs”

50. Pantograph Height
• At supporting mass, the
Dirichlet and Lagranian
boundary condition = 0.
• Some ‘marching steps’ are set
to 0 to satisfy boundary
conditions enclosed by the
FEA model.
• Assumption based on perfect
masts, no longitudinal, lateral
& latitudinal offset of OHLE at
supporting masts.
• Cauchy condition to ensure
that the wire displacement to
only have one unique solution.
19/10/2015 50

51. Pantograph Height
• Presence of dropper
wires also mean
alternative method, a.k.a.
Euler-Bernoulli theory
may also give reasonable
estimation.
• This gives us accurate
prediction of wire
deflection.
• Since wire cross-section
area at ends does not
make electric contact,
Timoshenko theory can
be neglected.
19/10/2015 51

52. Pantograph Height
• From the FEA model we observed that the point of
contact descends (then ascends) gradually in
between two support masts.
• The messenger wire is tensioned to keep height
variations of the contact wire in absolute minimum.
• When pantograph pushes against the contact wire,
the internal forces of both wire & pantograph can
be modelled using the Kelvin-Voigt model.
19/10/2015 52

53. Source: “Influence of static and dynamics on high
performance catenary designs”
19/10/2015 53

54. Pantograph Height
• Given the OHLE height is
lowered, the ‘stiffness spring’ in
the pantograph will become
compressed but the pantograph
is unable to be adjusted
quickly, due to viscosity in the
‘model damper’.
• Alternatively, when OHLE
height increased, the stiffness
spring expands but damper
cannot react rapidly, causing
pantograph tensile stress to
increase (if pantograph is
modelled as a series of
Standard Linear Models with
connection boxes).
19/10/2015 54

55. Pantograph Height
• If the model is valid, to allow further
analysis…
• We need to assume that the stiffness ‘k’,
masses and the viscosity of damper cannot
be altered.
 Analogous to:
Stiffness = resistance to torsion/tensile
strength of pantograph arm;
Mass = incurred mass at pantograph;
Viscosity = the ability of the pantograph
withstanding compressive force.
• Therefore…
Force exerted by the pantograph must be
changed to overcome the problem….
Otherwise…
19/10/2015 55
Source: “On Modelling
and Control of Pantograph
Catenary Systems “ –
Walters et al.

56. Bending strain caused by pantograph sliding rapidly.
Source: Japan Railway Technical Research Center
19/10/2015 56

57. • Different displacements from dropper wire would differ
the extent of wire rotation, hence different bending
stress. Further from dropper wire, higher the degree of
freedom, higher the stress is.
19/10/2015 57

58. • Hence, if the pantograph force does not satisfy the
(worst) boundary condition the wire undergoes fatigue
process.
19/10/2015 58

59. Pantograph Motion
• Multi-directional Wind
• This effect becomes apparent at high speed due to
viscous effects of fluids.
• However wind from latitudinal directions poses a
significant design challenge for newer pantograph.
• Stress analysis of pantographs need to be robust to
ensure that mechanical failures in different
directions can be prevented at the first opportunity.
19/10/2015 59

60. • Top:
CFD Modelling of
longitudinal flow
around pantograph.
(Source: ara.com)
• Bottom: Sidewinds
might provoke
significant
consequences to
railways.
(Source: Chris Baker
(University of Birmingham) -
The effect of unsteady cross
wind forces on train dynamic
behaviour)
19/10/2015 60

61. Pantograph Motion
• Possible wind effects:
• Loose electric contact
(if contact strip can be modelled as an aerofoil)
• Pantograph sway
(mitigated by wind impinging in any directions)
• Air borne particles
Dusts and particulates can cause contamination in
carbon strip, however as train travel at higher
speed this becomes inevitable.
19/10/2015 61

62. Pantograph Motion
• Other causes of pantograph motion includes:
 Sway
• Tilting trains
• Track cant
 Yawing motion
• Hunting oscillation
 Compressive/tensile movements
• Train bouncing
19/10/2015 62

63. Pantograph Motion
• Swaying refers to the
rolling motion of the
pantograph about both
longitudinal and lateral
axis of the train.
19/10/2015 63
Figure outlining train
axis nomenclature.
Source: Dr. Simon
Iwnicki (Handbook of
Railway Vehicle
Dynamics)
Brief
illustration
on deviation
of
pantograph
(swaying)
Source:

64. Pantograph Motion
 Sway
• Tilting trains
Designed to overcome
inertial and centripetal
forces around tight curves,
by slanting at an angle
using actively-controlled
mechanisms.
• This enables increased
speed and reducing
customer discomfort.
19/10/2015 64

65. Pantograph Motion
• If trains could be tilted…
why can’t pantographs?
• The pantograph tilts in
counter-direction relative
to the car body, offering
the same lateral offset
between the pantograph
and the contact wire.
19/10/2015 65

66. Pantograph Motion
• Hydraulics
Known as passive
control
The pantograph is fitted
with a counter-hydraulic
tilt system.
• When body tilts the
hydraulic will tilt
supporting rod sideways,
thus remaining the
pantograph in place
using rolling guideways.
19/10/2015 66
“Pantograph Dynamics
and Control of Tilting
Train” – Luo et al.

67. Pantograph Motion
• The tilt angle of the pantograph is the reverse of
the car-body tilt, hence
19/10/2015 67
Rank 2 -
Rotational Tensor
Co-ordinate
displacement of
pantograph,
relative to rolling
guideway
Tilt angle of car-
body relative to
gauge

68. Pantograph Motion
19/10/2015 68

69. Pantograph Motion
 Sway
• Track Cant
Also known as superelevation.
• To permit trains without tilt to travel at curves without
compromising lateral considerations.
• Also reduce wheel flange wear due to correct wheel-
rail contact.
19/10/2015 69

70. • Illustration of difference of rail top level.
(Wikimedia)
19/10/2015 70

71. • Illustration of Pantograph/OHL Relationship with track cant
(credits to Clive Mortimore)
Photo resized to fit frame dimension.
19/10/2015 71

72. Pantograph Motion
• Hunting Oscillation
• A railway wheel consist of a flat base and a flange.
For simplification purposes we model it as purely
conical.
• If two cones connected with a rod is placed freely on a
railway track, it has 2 main degrees of freedom:
 Yaw angle (a)
 Lateral displacement (b)
• Hunting motion can be explained using wheelset
pressure (Hertzian) and forces (Kalker’s theory), but this
is oversimplified.
We treat it as a cause to such secondary system
oscillation.
19/10/2015 72

73. 19/10/2015 73
a
b

74. Pantograph Motion
• Train bouncing
• Movements of a train in latitudinal direction (i.e.
along height of the train).
• Causes
 Trackbed & Ballasts
Due to soft track base, weight force is not
supported properly.
Causing isolated train vibrations
 Suspension
Modelled as viscous device that aims to reduce
train bouncing as possible. It reduces the extent of
latitudinal displacements.
However, if suspension is not stiff enough then as
axle loading (AW) increases, train bouncing also
propagates simultaneously.
19/10/2015 74

75. Pantograph Motion
• Conseqeuces of
sway:
• Dewirement
• Infringement of gauge
clearances in tight
railways
19/10/2015 75
Pantograph dewirement.
Source: HameyVision

76. • An example on
pantograph failure
caused by sway.
19/10/2015 76
Source: UK Rail
Accident Investigation,
5 Jan 2012

77. 19/10/2015 77
Source: UK Rail
Accident Investigation,
5 Jan 2012
• An example on
pantograph failure
caused by sway.

78. Pantograph Motion
• We scrutinised many possible causes to
pantograph motions…
• Given that we know how pantographs could fail,
it is possible for us to prevent / reduce the
extent of such damages.  crucial!
19/10/2015 78

79. Pantograph Sensors
• Systems are placed at
lineside to monitor
environmental attributes,
therefore permitting
actions or prediction to be
taken.
• The parameter in
investigation can be of
any type: ranging from
earthquakes, wind, rain,
… etc.
19/10/2015 79

80. Pantograph Sensors
• A hierarchy diagram of a Siemens SICAT PMS System.
19/10/2015 80
REPOR
T
FEEDBACK

81. Pantograph Sensors
• Side-wind detector:
The objective is to monitor
and inform wind condition
and irregularities to the
Control Centre/Signalman
and to the interlocking
systems.
• Temporary Speed
Restriction (TSRs) will
implement when
undesirable metrological
conditions are observed.
19/10/2015 81
Logytel Side-Wind Detector in
Spanish AVE Lines.

82. Pantograph Sensors
• Pantograph Monitoring System
As shown previously, carbon strip can cause torn
down of an entire OHLE system.
• New lineside system developed to capture and
scrutinise high-speed photographs taken of the
pantograph.
• A brief working flowchart:
19/10/2015 82

83. Pantograph Sensors
19/10/2015 83
Train passes
through a
beacon/coil
Is train detected?
Activate camera
High speed
photographs
Analyse
photographs,
locating
pantographs
Algorithm to locate
carbon strip
Check against
reference value,
determine wear
Warning and report
IF value < threshold
IF = YES
IF = NO

84. Pantograph Sensors
• Motto:
Detecting early symptoms of defect:
Prevent severe consequence
Detecting smaller defects
Preventative maintenance can be taken;
hindering propagations of any plausible
problems
• Why?
By proactively managing problems, the overall cost
implications caused by downtimes can be reduced
significantly.
19/10/2015 84

85. Pantograph Sensors
• Some ‘non-affiliated’ commercials:
• Pictures taken from high speed
camera (top & middle) shows how it
can give early indications of
pantograph wear.
• Pictures at depot (bottom) reveals
how these sensor can help train
operating companies (TOCs) to
respond quickly, controlling further
train defects and causing severe
delays.
19/10/2015 85Pantolnspect Inspection System

86. 19/10/2015 86
Pantolnspect Inspection System

87. 19/10/2015 87

88. Pantograph Sensors
• Shear strength in carbon strip remains a decisive
factor in pantograph failures.
• Force detection in carbon strip becomes crucial.
• Strain gauge and accelerometer installed on
pantograph head can help determine the force
parameters.
19/10/2015 88

89. Pantograph Sensors
• Strain gauge installed to deduce tensile and shear
stresses present on the pantograph head.
• Accelerator to detect dynamic irregularities caused by
defective, worn OHLE wires.
19/10/2015 89

90. Pantograph Sensors
19/10/2015 90

91. Qualitative Standards
19/10/2015 91

92. Qualitative Standards
• Different countries have
established varying
Standards in railways.
• The European standards
(EN) remain the
commonly occurring
examples and forms the
basis of our investigation
here.
• The British Standard (BSI)
will also be investigated
as it is also implemented
worldwide.
19/10/2015 92

93. Qualitative Standards
19/10/2015 93
to ensure…
… contact to
catenary is
established, …
… minimal
energy loss,
… limited wear &
tear to the
system,
… reduced risk
of disruption,
… hence
enhancing
reliability,
safety of
routine
revenue
operations.
… hence
risk
mitigation
can be
achieved.
Why do
they
exist?

94. Qualitative Standards
• Gauge:
EN15273-1 (pantograph, structural, mechanical,
electrical insulation gauge)
• “3.23
pantograph gauges and interface with the overhead
contact line system
specific reference profile combined with specific
associated rules allowing verification that the pantograph
head remains inside the allotted space, and location of
infrastructure structures at a sufficient mechanical and
electrical distance according to the pantograph head
type used with live or insulated parts.”
19/10/2015 94

95. Qualitative Standards
• Aims:
• For raised pantographs to remain within their allotted
space;
• Ensure that pantograph and associated profiles to be
cleared of any structures, taking in addition care of
maintenance allowances;
• Ensure clearances are maintained at two different
electric potentials to permit enough atmospheric
electrical insulation
19/10/2015 95

96. Qualitative Standards
• Typical pantograph gauge w.r.t. height:
(in millimetres)
19/10/2015 96

97. Qualitative Standards
• From below diagram it is evident that the width of the
pantograph is not a point of concern; however the
space swept by pantograph head is.
• Source: BS EN 15273 2 2013
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98. Qualitative Standards
• Interface:
EN 50318
• The interface parameters between OHL and pantographs are
specified.
This includes:
• Force of contact
• Modelling method
19/10/2015 98

99. Qualitative Standards
• Aims:
• To establish an uniform method for system analysis
and validation.
• To standardise parameters and tolerances within
tests.
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100. Qualitative Standards
• Flowchart illustrating a
benchmark procedure to
evaluate the parameters
within the OHL and
pantograph system.
• As specified in BS EN
50318.
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101. Qualitative Standards
• Table showing the standard of measurement tolerances:
Source: BS EN 50318:2002
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102. Qualitative Standards
• Table showing the standard measurements from modelling:
Source: BS EN 50318:2002
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103. Qualitative Standards
• Table showing the standard measurements from modelling:
Source: BS EN 50318:2002
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Nomenclature
Fm:
Arithmetic mean
value of forces over
certain distance
σ :
Standard deviation

104. Qualitative Standards
• Table showing the standard measurements from modelling:
Source: BS EN 50318:2002
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Nomenclature
Statistical
Maxima:
Fm + 3σ
Statistical Minima:
Fm – 3σ

105. Qualitative Standards
• Table showing the standard measurements from modelling:
Source: BS EN 50318:2002
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Arithmetic mean
and S.D. analysis
are used as force
varies over a long
distance due to
mechanical and
viscous (high
speed) dynamic
effects.
As such S.D. is
used as a standard
to regulate such
fluctuations.

106. Qualitative Standards
• The BS EN 50318 also
concerns how the
model is constructed by
setting out the
requirement for which
parameters must be
considered and
exploited, in a
standardised manner.
• Reference model is the
standard framework that
allows the analysis on
the system.
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107. Qualitative Standards
• Installation:
EN 50119
• The standard related to pantographs concern the
tests required in compliance with the rest of the BS
Standard.
• Aims:
• The stringent test requirements are system
assurance procedures to ensure that each sub-
systems are compatible against each other.
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108. Qualitative Standards
• System tests
• For a new installed system, it should be line-tested in full
scale to ensure quality requirement of the standard is fulfilled
at a given running speed.
• To fulfil electrical and mechanical line parameters, both static
(dimensional validation) and dynamic requirements,
successful candidates shall be within design tolerances.
• Acceptance tests
• To ensure compatibility.
• Commissioning tests
• To ensure the electrical integrity of the system is not
jeopardised and is in accordance to design requirements.
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109. Pantograph Testing
• When a new pantograph is manufactured, we need
to understand the extent it conforms with
International Standards (i.e. EN).
• Test rigs and methods are developed to assist us
with the investigation.
• Modelling of complex dynamic behaviour remains
to be the key in such development.
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110. Pantograph Testing
A pantograph test bench – however no aerodynamic force can be measured.
Source: PANTOtrain
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111. Pantograph Testing
• As mentioned
previously, viscous
effects become dominant
at high-speed
application.
• Methods to measure and
determine these forces
require new instruments.
• Source: Fibre Optic Sensor Instrumented
Pantograph As Part Of A Continuous
Structural Health Monitoring System For
Railway Overhead Lines (Wagner et al.)
19/10/2015 111

112. Pantograph Testing
Pantograph – Catenary Interaction Simulator
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Air flow
outlet

113. Pantograph Testing
• Using Bernoulli’s Equation, if we measure air velocity
below and above the pantograph head…
It is possible to determine fluid parameters.
• Pitot tube is the measuring instrument for aerodynamic
force.
• Wind speed, pressure … etc are fluid parameters that can
be determined using a pitot tube.
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114. Pantograph Testing
When air flow gains speed they lose static pressure, hence
using a pre-calibrated pitot tube, the change on fluid level
would indicate a pressure-differential.
… hence aerodynamic force is determined (laminar flow
assumption).
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115. Pantograph Testing
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Aerodynamic forces

116. Pantograph Testing
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Bernoulli’s Equation:
P = static pressure
rho = density of air flow
v = velocity of air flow
g = gravitational
acceleration
frac{1}{2}rho v^2
= dynamic pressure
component of
ambient air flow
rho g h= gauge
pressure

117. Pantograph Testing
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Finite Analysis:
F_i = Force exerted at point
mass
A = Area of point mass
i = displacement notation
of point masses
n = number of point
masses concerned
limit = to gradually split
point masses into
smaller marching
steps
delta = increments
nabla = increments with
nearby point masses

118. Pantograph Testing
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Bernoulli principle allows us to
determine the static force at any
instant in the pantograph concerned.
The Finite Analysis exploits the force
exerted on a point mass, in order to
find the behaviour of the rest of the
pantograph. However, the shearing
stress is not analysed here; it simply
adds up all individual force and treat
aerodynamic forces as one.

119. Pantograph Testing
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Aggregate Contact
Force to the catenary

120. Pantograph Testing
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F_c = total point force
F_sensor= force reading from an
arrangement of strain
gauges
M_pointload
= mass of point mass
a_sensor= accelerometer reading
F_aero = aerodynamic forces
F_c = total contact force
k_f = number of sensors
m_above = total pantograph mass
k_a = number of
accelerometer
Summation of points:
Single point:

121. Pantograph Testing
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The process denotes
how contact forces are
evaluated.
Assuming there are ‘f’
number of sensors, we
progressively add up
tiny force contributions
to form an aggregate
contact force.
Summation of points:
Single point:

122. 19/10/2015 122

123. 19/10/2015 123
Kelvin Lam
Thanks for your attention.
Any questions?