Theoretical and Practical Aspects of Harmonics from a Railway Traction System Supplying Line

The paper deals with the influence of railway systems over the supplying line. Firstly, the configuration of an electric railway traction system using power electronics in Electric Multiple Units is presented. Details are provided for the electric driving system components which can influence the harmonic distorting regime (single phase traction transformer, asynchronous traction motors, power inverters and converters, static power converters and contact line). Theoretic and practical considerations related to them are included. Dynamic effects of the voltage harmonics from the power supplying network are presented. Overvoltages caused both by the power supplying network instability and respectively by current harmonics are discussed. Experimental results concerned with the instability aspects due to electric resonance at a frequency of 800 Hz were analyzed and the condition to prevent them was deduced, along with the technical solution. Experiments made before and after the designed filter introduction proved its design and implementation correctness. Overall and per-harmonic influence of the filter was revealed.