Page 55 - 360.revista de Alta Velocidad - Nº 5

Current situation and prospects of electric traction systems used in High-Speed railways

Figure 1. Basic diagram of a power electrical system (general and railway system). Diagram is represented by all the elements
necessary for a train with electric traction to operate. In the most common case: 1) Generation sub-system (central of gene-
ration); 2) Sub-system Transport (transmission line); 3) Sub-system Distribution (distribution line); 4) High-Speed TPS (traction
substation, single-phase electric transmission line to the train (catenary) and train); 5) DC Conventional TPS (traction substa-
tion, DC catenary and train). (Source: Author).

The function of the transmission line is to transport large powers from the generation plants to
the centers of the load and to the large industrial consumers that exceed the normal limits of
the distribution lines. This would be the case of the High-Speed rail, which, due to its power
demand, requires a direct connection to the transmission line. This type of line has sufficient
short-circuit power to ensure the correct operation of the rail. In this case, therefore, the
distribution line is dispensed with and the transmission line is used directly as the distribution
line.

3. Source of disturbances

High-Speed trains that operate with industrial frequency (network frequency) are a source of
disturbances in the power lines and the own railway environment. It is a load powered by single-
phase alternating current, variable in space and time, and power electronics of locomotives.
This electronics produces harmonic components of the traction current that flows through
the catenary and then returns to the nearby terrain. This fact complicates the operational
scenario, taking into account that the rest of the railway systems require electrical cables for
their operation.

Although the single-phase alternating current offers an important advantage over the direct
current as is its ease of transformation, as a disadvantage is its property of inducing voltages in
parallel conductors. Note that in the normal use of alternating current in three-phase systems,
the inductions of each phase are compensated by the inductions of the other phases. This fact
does not occur in single-phase electrification as there is an electromagnetic disturbance that
may be important for other railway installations.
For all of the above it can be said that electrification causes disturbances in the electrical
environment of the High-Speed line. These disturbances occur both on the transmission line (as
a consequence of being connected to it) and in all the electrical and electronic installations of
the railway line.

International Congress on High-speed Rail: Technologies and Long Term Impacts - Ciudad Real (Spain) - 25th anniversary Madrid-Sevilla corridor 53