IEEE Electrification Magazine - September 2013 - 8

hand, the pantograph consists of a
sliding collector equipped with the
contact strips, called skates or pads,
located on an articulated frame,
which tries to follow the contact wire.
Pantographs can be classified
depending on their mode of operation
(passive versus active) or the characteristics of the line (ac versus dc).
While the force that pushes the
strips of a passive pantograph against
the contact wire is constant in time,
this force varies within an active one
due to its integrated and complicated
control systems. Although passive
pantographs are the most inexpensive and widespread, technical developments in recent years have begun
to put active pantographs on the
market at competitive prices. Indeed, the monitoring and
control of contact forces is becoming an effective way
to face the problems associated with the catenary-pantograph interaction at high speeds.
The electric nature of the line, ac or dc, leads to the
mechanical design of the catenary and pantograph,
resulting in almost antagonistic technical solutions. AC
pantographs work with higher voltages, which is mainly
because the locomotives running within this type of system do not need large current intensities. Therefore, ac
catenaries are consequently lighter, implying that the
force applied by the pantograph must be as low as possible to prevent excessive displacements of the contact
wire. On the contrary, dc pantographs are designed to
exert a significantly stronger force because it is believed
that the current can be interrupted if the contact force
falls below a reasonable level.
For the sake of safe interoperability, the European Committee for Electrotechnical Standardization (CENELEC) was
asked by the European Commission (EC) to prepare

The main difference
between the railway
electrification system
and power
transmission or
distribution lines is
its inherent difficulty
of feeding the
rolling stock as a
moving load.

Positive Feeder

Positive-Phase Wires
Negative-Phase Wires
Neutral Wires

Negative Feeder Messenger Wire

Return Wire

Contact Wire

Rail
Cross Section

Longitudinal Section

Figure 5. A cross section of an OCL.

I E E E E l e c t r i f i c atio n Magaz ine / september 2013

exhaustive norms for railway systems
and, particularly, for OCLs. Clearly, the
combination of diverse OCLs and pantographs provides different interaction performances. Regarding this
diversity, the European Standard EN
50367 defines the parameters for
interoperability in the field of interaction between both of the subsystems.
The infrastructure manager must
ensure that the values for the geometrical characteristics of the OCL and
the pantographs fulfill those specified
in the norm, according to the type of
infrastructure. The same document
also specifies the interface requirements of infrastructure and rolling
stock to reach free access to the European railway network. However, the
aim of Standard EN 15273 is specifically to define the
space to be maintained and cleared to allow the running
of rolling stock. Moreover, the rules for the calculation and
verification of the sizing of the rolling stock to run on a
single infrastructure or on different infrastructures without any interference risk are also established. Finally, the
European Standard EN 50119 specifies the structural
requirements and tests for the design assemblies and
individual parts of any OCL.

Catenary-pantograph Dynamic Interaction
The limitation on the top velocity of high-speed trains is
related to the ability to supply the proper amount of
energy required to run their engines through the
catenary-pantograph interface. When there is a loss of
contact, not only is the energy supply interrupted but arcing between the collector bow of the pantograph and the
contact wire of the catenary also appears, leading to the
deterioration of the functional conditions of the two systems and causing an important injection of high-frequency
harmonic currents. An alternative
would be to increase the contact
force between the two systems. But
such an increase in force would lead
to rapid wear of the contact strip of
the pantograph and of the contact
wire, with negative consequences on
the durability of the system. These
situations require that the dynamics
of the catenary-pantograph interface
are properly modeled and that the
software used for analysis, design, or
to support maintenance decisions is
not only accurate and efficient but
also allows the modeling of all
details relevant to the train overhead
energy collector operation.

Table of Contents for the Digital Edition of IEEE Electrification Magazine - September 2013