IEEE Electrification Magazine - September 2013 - 7

(a)

(b)

Figure 3. (a) OCL and (b) pantograph photographs.

Overhead Catenary Line
The last element of the electrification system, which is
crucial in the railway context, is the OCL or the catenary.
This is the cable structure used to supply electricity to the
trains by means of the dynamic interaction between the
contact wire and the pantograph, i.e., a mechanical device
located in the upper part of the locomotive. -Figure 3
shows photographs of (a) an OCL and (b) a pantograph. One
of the key aspects of designing a railway catenary is
ensuring certain margins of its behavior when the pantograph is in contact; overall, the design of the OCL must
avoid any loss of contact between the contact wire and
the strips of the pantograph. Loss of contact is very undesirable since it can result in electric arcs, which increase
the wear of both elements and the mechanical stresses
when contact is restored.
Ensuring uniform contact forces require that the contact wire does not present large variations in height above
the rails. In situations where the train speed is not high,
close to 50 km/h, it may be sufficient to build only the contact wire. However, if the train speed increases, the lowest
uplift along any point of the contact wire is highly desirable, which is not possible with the simple contact wire

tension. A high-speed system should, therefore, use a catenary configuration with two cables, one for providing the
electric energy and the other for supporting the first one.
Besides these main components, a high-speed catenary is
comprised of other elements that also have their influence on the behavior of the cable system, which is
described below.
As discussed earlier, it is typical to distinguish
between high-speed catenaries, metropolitan railway
catenaries, etc., depending on the characteristics of the
railway system. The most common and widespread OCL
is similar to that shown in Figure 4, which consists of
three basic elements: 1) the messenger wire, which supports the cable system; 2) the contact wire, which feeds
the vehicles; and 3) the droppers, vertical cables that
connect electrically and link mechanically by means of
clamps on the messenger and contact wires. The initial
equilibrium of the cable system is not a trivial problem
but a very complex one, and some mathematical algorithms have been developed for this purpose.
Electrically speaking, additional feeders are sometimes
needed, depending on the system configuration and the
energy demand, as depicted in Figure 5. On the other

Span
Dropper

Contact Wire

Messenger Wire

Pantograph

Catenary
Vehicle

Figure 4. An OCL and pantograph scheme.
	

IEEE Elec trific ation Magazine / s ep t em be r 2 0 1 3

7



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

IEEE Electrification Magazine - September 2013 - Cover1
IEEE Electrification Magazine - September 2013 - Cover2
IEEE Electrification Magazine - September 2013 - 1
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IEEE Electrification Magazine - September 2013 - Cover3
IEEE Electrification Magazine - September 2013 - Cover4
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https://www.nxtbook.com/nxtbooks/pes/electrification_september2019
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https://www.nxtbook.com/nxtbooks/pes/electrification_june2018
https://www.nxtbook.com/nxtbooks/pes/electrification_december2017
https://www.nxtbook.com/nxtbooks/pes/electrification_september2017
https://www.nxtbook.com/nxtbooks/pes/electrification_march2018
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