Knowing the FACTS

The increase in traffic on existing tracks, combined with new high-speed rail projects mean rail traction is fast becoming an important load on electric supply grids. This in turn is focusing a lot of attention on voltage stability, as well as the power quality of the surrounding grids. Trains taking power from the catenary need to be sure the supply voltages are stable and do not sag. Voltage and current imbalances between phases of AC supply systems must also be confined in magnitude and prevented from spreading through the grid to other parts of the system. Voltage fluctuations and harmonics need to be controlled if they are to stay within the stipulated limits.