Voltage unbalance vulnerability areas in power systems supplying high speed railway

High speed railway loads fed by the three phase power system represent an important source of unbalance perturbation in the grid. The degree of voltage and current unbalances depends on the train motion, load condition and power system supply configuration. The present paper deals with the identification procedure of a vulnerability area in which the voltage unbalance presents values that exceed the standard limits. A case study referred to the 63 buses CIGRE network analyzed in the paper gives rise to interesting comments and discussion.