Converter substations
Introduction
A traction substation is an electrical substation that converts electrical energy from the form provided by the general network to conditions of voltage, current and frequency appropriate for use in means of transportation such as railways (including trams and related means) or trolleybuses.
This may involve the conversion of a three-phase system at industrial frequency (50 Hz or 60 Hz) to lower frequencies, its conversion to a single-phase system in alternating current or its rectification to provide direct current according to the requirements of the electric motor to be powered.
A railway electrification system includes the set of elements that make it possible for electrical energy to reach the mobile unit, with the necessary power so that it can achieve the performance for which it has been designed.
Therefore, an electrification system comprises three large blocks:[1].
The classification of substations takes into account different criteria:[2].
In general terms, a traction substation is the installation in charge of connecting the electrification sections to the three-phase transmission network. To do this, they transform voltages from the levels of the three-phase network to those of the catenary "Catenary (railway)"), with prior rectification in the case of direct current systems.[2].
Generally, traction substations have a simple bus topology. The reasons for this respond to the main advantages of this type of topology compared to other more complex ones. These advantages mean lower cost and greater flexibility. However, when it is intended to feed several lines from the same substation, it is advisable to use more complex topologies such as ring or double bus.[2].
Regarding the way of connecting the substation to the three-phase system of the public network, two ways of connecting are distinguished:[2].
Direct Current Traction Substation
Contenido
Por lo general, las subestaciones de tracción de corriente continua, alimentan catenarias a tensiones que van desde los 600 V a los 3.000 V, aunque realmente las tensiones de alimentación son ligeramente superiores a estas teóricas, ya que hay que considerar las pérdidas en las líneas (p. ej. tener una tensión de 3.300 V a la salida de la subestación de tracción para alimentar una línea convencional de 3.000 V). Los componentes de las mismas son muy similares a las subestaciones de tracción de alterna. Sin embargo, se incluye el puente rectificador que las hacen ser un poco más complejas. Además, si se trata de una subestación reversible, esta debe poseer un equipo inversor que permita devolver la energía eléctrica desde la catenaria hasta la red de distribución.