Public supply disturbance from AC traction

Electricity supply authorities are increasingly expected to supply disturbing loads, i.e. to railways who do not take a balanced 3-phase current and/or a sinusoidal current waveform. Consequently the supply voltages acquire these irregularities and could make other customers´ equipment maloperate. The causes and effects are briefly explained. An AC traction supply is a type of disturbing load in two respects. It inherently requires a single phase supply and the locomotive takes a rectangular current waveform. The author gives guidance on predicting the likely disturbances based on years of experience in the UK. An illustration is given of the calculation. The emphasis is on the prediction of disturbances. For brevity it is assumed that traction supplies are via 132/25 kV single phase transformers, connected line to line