Page 58 - 360.revista de Alta Velocidad - Nº 5
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Martínez Acevedo, José Conrado. Berrios Villalba, Antonio. Peregrín García, Eugenio.
3.3 Passive techniques to reduce imbalance
Different passive solutions have been introduced for minimizing the effect of voltage unbalance.
Although the ideal solution for the railway operation would be to connect the traction substations
according to Figure 5A, in practice the substations are connected alternately to the phases of
the network as shown in Figures 5B and 5C. Such connections are often referred to as pure
single-phase connections. Consequently, the voltages between different feeding sections are
60° or 120° out of phase, so that the network must be sectioned for isolating the paths fed
from different substations or different transformers. The phase separation of different feeding
sections is done by so called neutral sections.
In the case of Figure 5B it is said that the phase rotation is by electrical substation (the two
transformers are connected to the same phase). In the case of Figure 5C the rotation is by
transformer.
Figure 5A. Pure single-phase connection (ideal but not possible). (Source: Author).
Figure 5B. Pure single-phase connection (phase rotation by electrical substation). (Source: Author).
Figure 5C. Pure single-phase connection (phase rotation by transformer). (Source: Author).
56 360.revista de alta velocidad
