Pantograph wear assesment in overhead conductor rail systems P. Rodríguez, B. Suarez, J.A. Chover, J. Terrón andJ.D. Sanz

Wear is the phenomenon that determines the Hfetime of the collector strips. Since wear is an inevitable effect on pantograph-catenary systems, it is necessary to determine optimal operating conditions that can mitígate its effects. In this study we have performed a simulation model of the pantograph-overhead conductor rail system which allows the evaluation of the dynamic conditions of the system through the contact forcé. With these results we have made an evaluation of the quality of current collection, a calculation of the pantograph wear and a definition of the optimal operation conditions of the pantograph-overhead conductor rail system.

PANTOGRAPH WEAR ASSESMENT IN OVERHEAD CONDUCTOR RAIL SYSTEMS

Pablo Rodríguez, Berta Suarez, José A. Chover, Jorge Terrón and Juan D. Sanz Research Centre on Railway Technologies (CITEF). Universidad Politécnica de Madrid

C/Jose Gutiérrez Abascal, n°. 2, 28006, Madrid, SPAIN e-mail: citef-prodriguez@etsii.UPM.es

Abstract

Wear is the phenomenon that determines the lifetime of the collector strips. Since wear is an inevitable effect on pantograph-catenary systems, it is necessary to determine optimal operating conditions that can mitígate its effects. In this study we have performed a simulation model of the pantograph-overhead conductor rail system which allows the evaluation of the dynamic conditions of the system through the contact forcé. With these results we have made an evaluation of the quality of current collection, a calculation of the pantograph wear and a definition of the optimal operation conditions of the pantograph-overhead conductor rail system.

1. INTRODUCTION

Wear is the phenomenon that determines the lifetime of the collector strips, which establish the necessary contact for driving power from the catenary to the pantograph in railway vehicles. Since wear is an inevitable effect on pantograph-catenary systems, it is necessary to determine optimal operating conditions that can mitígate its effects.

The objective of study is to carry out a dynamic analysis of the system pantograph-overhead conductor rail, in order to study the conditions that allow a correct quality of current collection system and within these, which are those that maximize the life of collector strips, due to a lower wear.

This work has been developed within the Research Centre on Railway Technologies (CITEF). This Centre has an experience of a decade in dynamic simulation of pantograph-catenary systems [1-4].

2. DYNAMIC ANALYSIS. QUALITY ASSESSMENT OF CURRENT COLLECTION

It has been employed a model of the pantograph-overhead conductor rail system that combines simulation techniques of multibody systems with calculation by finite element, to consider the flexibility of the overhead conductor rail.

Figure 1. Model of the pantograph-overhead conductor rail system

In this model the main parameters of the system analyzed have been taken into account, carrying out variations of these to identify their influence, both in the quality of current collection as in the wear of the pantograph. These parameters are: distance between supports (8 and 10 m), stagger type (sine or linear), static forcé (between 50 and 200N), speed (between 50 and 150 km/h) and pantograph type (it has been modeling two types, corresponding to a metropolitan train and a suburban train).

The quality of current collection has been assessed in accordance with the criterion of the current standards through the contact forcé obtained in the simulations. It has been used statistical criterion as well as the percentage of take-offs.

• Statistical criterion: Taking into account the statistical distribution of valúes of the contact forcé, will define the next quotient is defined:

3<7F

where aF is the standard deviation of the contact forcé, and Fm is that forcé media. For valúes below unity the quality of current collection will be guaranteed.

• Calculation of the percentage of electric ares: This method determines the proportion of take-offs by calculating the term:

L torco NQ = t total

xlOO

which, for valúes less than the 0.14%, will ensure correct capturing quality.

Both the statistical parameter of the contact forcé as the percentage of take-offs are plotted against the static forcé and velocity, for each pantograph model and distances between supports (8 and lOm).

Static Forcé [N]

Figure 2. Statistical quotient (Je) against the static forcé and velocity

These results have led to the conclusión that an increase in velocity implies an increase in the valúes of Je and NQ, and therefore a lower quality of current collection (Figura 3a). On the other hand, the variation of static forcé has shown minimal valúes of Je and NQ, and therefore, optimal conditions of operation of the system for a particular valué of static forcé (Figura 3b).

^ - F ^ 5 0

I - F O 7 0

F-090

F - l l ü

F-130

Í F - 1 5 0

V O S ! V-060 V -070 V-OSO V-OSO V-10O V-11C V-120 V-12J9 V-14D \

Speed [Km/hl

a) Against speed. Constant staticforcé b) Against static forcé. Constant speed

Figure 3. Statistical quotient (Je)

The results of the simulations nave revealed the conditions that lead to a better quality of cunent eolleetion, as well as rejeet those cases with some unaeeeptable conditions. These results have been a previous filter. Only conditions which satisíy both entena have been objeet of study of the wear produced. The following table summanzes the cases that meet the statistical criterion (E) or the percentage of take-offs (A), for each pantograph model (A o B), distance between supports, static forcé and speed.

E - Statistical criterion

A - Percentage of take-offs

•/ - Acceptable

X- Unaeeeptable

Modal A

h -:--.í

f.yíi) F-090

F-110

F-130

F-1S0

F - I B O

F 200

V-060

E | A

V-060

E | A

V-070

E | A

V

r A

v o s o

E l . V

E

JO

A

•

•

•

' .

1 V-110

r a V-120

E A

V 1 •

E | A

V-140

r A

V-150

E A • »

E « .

F J 9 0

' • " '

,.,„

V-050

El* V 0 6 0

E | A

V-070

t | «

v-oeo E | A

- • " • •

E | A

V

« V-110

,l> V-120

F. A

V-1 Í0

E | A

V-140

E | »

V I 60

E|.

Model A - lOm Model B - lOm

Modal A

F-050

F-070

F-090

F-t10

F-130

F-150

F 180

F-200

, « 0

E | .

V-060

L | A

V :• ' •• .

E | »

'.' :- •

E A . -E | .

V-100

E A ».„. ».,„ V- 1 X

E | «

v-uo E A

V - , »

f oso

F 070

F-090

• 110

F-130

! IbO

• 1S1J

1 2W

voso

.|. v-oeo , | A

V 070

• 1» V-080

• 1» V-090

,|. v-ioo

• l« v 11U

,|. V l i o

• l . V-1J0

,|. V 140

•1» v VM

,|.

Figure 4. Quality assessment ofeurrent eolleetion

WEAR MODEL

In order to model pantograph wear is necessary to use an equation that include the contribution to the rate of wear both of the contact forcé, electric cunent and the appearance of electric ares, but at the same time taking into consideration the influence that each of these phenomena performs on each other [5] [6]. Thus, not considering the contribution by arches that have been removed in the preceding paragraph, the next equation has been used:

A = (í + i0)n 4K

Where the kF, kt and n constants are known for the bibliography, and the other data, contact forcé (Fe), sliding velocity (V) and electric cunent (i) are calculated through the results from dynamic simulations and the resolution of the equivalent eléctrica! circuit of the railway system. This model has

allowed to obtain the curve of pantograph wear (wear depth for each point of the collector strip width), by the addition of the contributions mechanical and electrical.

Collector Strip Width [m]

Figure 5. Pantograph wear

The results (Figure 6) obtained for the mechanical contribution show as the peak valúes of wear are obtained when the pantograph pasat the points of passage through the supports. Besides increasing the speed or the static forcé leads to a higher mechanical wear. Mechanical wear is less with the linear stagger.

a) Constant static forcé

Collector Strip Width [m] Collector Strip Width [m]

-V_50 ^—V_60 V.70 — V_80 V 9 0 V_10O - - V _ 1 1 0 - - V _ 1 2 0 - - V.130 - - V . 1 4 0 - - V _ 1 S 0

5ire Linear

0,012

b) Constant speed

Collector Strip Width [m] Collector Strip Width [m]

F_50 F_70 F_90 F_11D F_130 F _ 1 5 0 - - F _ 1 8 0 - - F _ 2 0 O

Figure 6. Pantograph wear depth (h) - Mechanical contribution

In regards the electric contribution can be seen as, unlike the mechanical contribution, the points of passage through the supports present valleys in the pantograph wear. Thus, according to the preponderance of any contribution will be peaks or valleys in the total wear at the points of passage through the supports.

On the other hand, as for mechanical wear, increasing the velocity leads to higher electrical wear. However, the static forcé behavior presents a contrast to the previous case. An increase in the static forcé produces a decrease in wear due to electrical phenomena. The stagger type is not a relevant factor for the electrical contribution to wear.

•",

r\ i " . - « ' \

, • • —

*

•.

--

r\ f * *#*»* \

*

/ ' \

-

r\r , - \ r

I '4

I 0,0.

, \ - . " , / W \ , ' . - ' - , ,".---. />.-/•, ;\-.\

L V \L \L k l \t >

.' \ t • . ' - - ' "< -' ' • - ' ' -

• > • * • • • » , • • , ,

—A." .;ii^,.' \Z^~'. '

a) Constant static forcé

Collector Strip Width [rr Collector Strip Width [m]

-V_50 — V_60 V_70 V.80 ^ V _ 9 0 ^ V _ 1 0 0 - - V _ 1 1 0 - - V _ 1 2 0 - - V.130

Sine Linear

-V_140 - - V _ 1 5 0

-3QOOQÉ -ÜQÜÜÜÜ (—\l—\(—V—v—\i—^

b) Constant speed

Collector Strip Width [m] Collector Strip Width [m]

F_50 F_70 F_90 F_110 F_130 F _ 1 5 0 - - F _ 1 8 0 F_200

Figure 7. Pantograph wear depth (h) - Electrical contribution

Finally, the sum of the two contributions mechanical and electrical gives total wear. The increase in speed increases both the electrical wear as the mechanical wear, and therefore also total wear. However, the effects of static forcé for mechanical and electrical contributions are opposite and depend on the speed. Thus, at low speeds an increase of static forcé leads to a greater total wear, while at high speeds the effect is not predictable in principie. The linear stagger has a slightly smaller wear than the sine due to its effect on the mechanical contribution.

Linear

a) Constant static forcé

\r-"\/-\y'-'\/'-\\r

I

ttjn

?ÍI

. ' • ' \

..-.-.-.. * ' * ' * • A - k \ A-.'»

/ " \

/*'*'\ /"*">.

¡

Collector Strip Width [m] Collector Strip Width [mi

-V_50 V_W> V_70 V_80 V_90 V_100 - - V _ 1 1 0 V_120 - - V _ 1 3 0 - - V _ 1 4 0 - - V _ 1 5 0

0.020

¡

0.000

</y\'-* V j^Ois*!-

High speeds (130 Km/h) |

b) Constant speed

Collector Strip Width [m] Collector Strip Width [m]

F 50 F 70 F 9 0 F 110 F 130 F 150 F 180 F 200

Figure 8. Pantograph wear depth (h)

4. CALCULATION OF THE OPTIMAL OPERATING CONDITIONS. USEFUL LIFE OF THE PANTOGRAPH

Lifetime of the pantograph has been estimated using máximum wear of the contact strip. Thus, máximum useful life corresponds to the case with the smallest valué in the máximum depth of wear. From this result have been determined the optimum conditions of operation of the pantograph-overhead conductor rail system, which are those that define the case that leads minimum valué of the máximum depth of wear. For example, for each speed of movement there an optimum static forcé that provides minimal wear, see Figure 2.a. Results obtained for the different analyzed scenarios have been compared (type of pantograph, distance between supports, staggertype, etc., see Figure 2.b.).

0,0100

0,0050

0,0000

V-150 V-140

. V-130 V-120

V-110 V-100

' V-90 V-80

70 speed [km/h] 60

F-90 F _ 1 1 0

Statkforce[N]

F- 1 3 0 F-150 ,

DistancebetweensupporttBm

-•-A-Sni-Senoidal

-•"B-Sm-Senoidal

A-Sm- Linear

^B-8m-Linear

Jírs' rr*= '

V-50 V-60 V-70 V-B0 V- 0 V-100 V-110V-120V-130 V

Speed [km/h]

140 -150

a)Maximum depth wear against speed and static forcé

Figure 9. Optimal operation conditions

b) Máximum depth wear against speed (Distance between supports 8m)

The best operating conditions from the point of view of wear are obtained for the linear stagger, the distance between supports of 10 m and the model of pantograph A.

Representing the pairs of speed and static forcé valúes that lead to the máximum useful life of the pantograph we have obtained maps of optimum operation conditions. These diagrams will be very useful when selecting the conditions of operation of the system pantograph-overhead conductor rail.

Model A-Sm/Mcdel B-8m

V-50 V-60 V-70

A-Sm-L 50

B-8m-L 50

V-90 V-100 V-110 V-120 V-130

160

140

120

" 100

a S. so

£ &0

40

20

^ A - l O m - S

U B-lOm-5

A A-lOm-L

• B-lOm-L

Mode l A - 1 0 / M o d e l B-10

^ J / / / J *-/

j~S ¿/ A

V-W

50

50

50

50

V-60

50

50

50

50

V-70

50

70

50

70

V-80

50

70

50

70

V-90

50

90

50

90

V-100

50

150

50

150

V-110

50

150

50

150

V-120

50

150

70

150

V-130

90

130

90

130

V-140

90

130

V-1EO

130

130

Figure 10. Optimal operation conditions

CONCLUSIONS

The following conclusions can be made according to the variations carried out for each parameter:

• Stagger: The linear stagger presents a lower wear than the sine, for all conditions of speed, static forcé, pantograph model or distance between supports.

• Distance between supports: From the point of view of current collecition the models with a distance between supports of 8 m are associated with a more stable dynamic behavior. Nevertheless, minor wear valúes are obtained for distance of 10 m.

• Speed: Higher valúes of speed produce a higher system instability and therefore a lower quality of current collection. Also, the increase in speed leads to an increased of pantograph wear.

• Static forcé: The static forcé, as well as the speed, both mainly determines the quality of current collection and the generated wear. It has been observed that depending on the speed there is a static forcé optimal from the point of view of current collection quality and pantograph wear.

References [1] C. Vera, B. Suárez, J. Paulin and P. Rodríguez. Simulation Model for the Studyof

Overhead Rail Current Collector Systems Dynamics, Focussed on the Design of a New Conductor Rail. Vehicle System Dynamics, 2006, Vol. 44, pags. 595-614.

[2] F. J. González, J. A. Chover, B. Suarez, y M. Vázquez, Dynamic Analysis using Finite Elements to Calcúlate the Critical Wear Section ofthe Contact Wire in Suburban Railway Overhead Conductor Rails, Journal of Rail and Rapad Transit, 2008, Vol. 222, pp. 145-157.

[3] C. Vera, J. Paulin, B. Suárez and P. Rodríguez, Improved Design of an Overhead Rail Current Conductor for Application in Underground Lines, Railway Engineering - 2005, London, United Kingdom, 29-30 June, 2005.

[4] B. Suárez, J. Paulin y C. Vera, "Optimización de la Captación de Corriente con Catenaria Rígida", Actas del I Congreso Innovación Ferroviaria, Calatayud, España, 5-6 Octubre, 2004.

[5] A. Collina, S. Melzi y A. Facchinetti. On the prediction ofwear of contact wire in OHE Unes: a proposed model. Vehicle system dynamics. - 2002. - Vol. 37. - pags. 579-592.

[6] J.F. Archard. Contact and rubbing of fíat surfaces. Journal of applied physics.. -1953. - Vol. 24. - pags. 981-988.