Modern high-speed rail traction systems exert heavy and complex loads on supply grids, and the increase in traffic on existing tracks combined with new high-speed rail projects mean rail traction has quickly become an important load on supply grids. This is focusing much attention on the efficiency of the catenary, and the power quality of surrounding grids. Trains taking power from the catenary must ensure the supply voltages are stable and do not sag. Usually, power is taken between two phases, thereby causing substantial imbalance between phases in networks originally not at all built for this kind of operation. Unless remedied, the result will be deterioration of power quality, not only harmful to the traction system itself, but also prone to spreading through the supply grid, disturbing other users of power in the same grid.
Furthermore, sagging and fluctuating catenary voltages may result from heavy and varying consumption of reactive power by locomotives. This must also be addressed by means of dynamic voltage support of catenaries, thereby maintaining heavy traction capability despite weak feeding, and avoiding harmful voltage drops along the catenary.
In all these cases, time as well as money can be saved by implementing FACTS in existing systems rather than investing in costly and time-consuming reinforcement of the railway feeding infrastructure, for example, by building new transmission or sub-transmission lines, and/or building new substations and feeding points.
It is also worth mentioning that with FACTS in the system, adequate power quality can be achieved with infeed at lower voltages than would otherwise be possible. This means, for example, that it may be sufficient to feed a railway system at 132 kV rather than at 220 kV or even 400 kV, which will of course enable a lower investment cost and shorter implementation times.
FACTS for railways comprises SVC, SVC Light and Dynamic Energy Storage.
>> More about SVC and SVC Light
>> More about Dynamic Energy Storage
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