Estimation of Voltage Unbalance in Power Systems Supplying High Speed Railway

The electric high speed railway loads supplied by the three phase power system represent one of the main sources of voltage unbalance perturbation in the grid. The power system configuration and the load conditions influence the degree of this power quality perturbation. The present paper deals with the problems raised by the practical determination of the voltage unbalance factor in conformity with the European and IEEE standards. The procedure for identifying a vulnerability area in which the voltage unbalance presents values that exceed the standard limits is elaborated and comparison on the use of the two mentioned set of standards is performed. A case study referred to the 63 buses CIGRE network analyzed in the paper gives rise to interesting comments and discussion.