Harmonic problems in Queensland Railways electric traction system

Harmonic current distortion due to thyristor controlled locomotives is a well known fact to most railway engineers. The significance of such distortion, however, is dependent entirely on the proportion of the harmonic load to the power capacity of the electricity supply system. The author discusses the experience of Queensland Railways with respect to harmonics. Real time measurements were performed and load variations recorded. Simulation studies were also made to assist in predicting future load and consequently the harmonic level. To overcome the excessive harmonic levels it was decided that filters should be installed at all feeder stations in order to meet the standard requirements. The author discusses the filter design in particular the problems of capacitor failure