Conducted and Radiated Electromagnetic Interference in Modern Electrified Railways with Emphasis on Pantograph Arcing

University dissertation from Stockholm : KTH

Abstract: Arcing from the pantograph, a commonly observed phenomenon, is knownto be a major source of wideband electromagnetic emission which is more pronounced during the winter. Experience within the railway industry has shown that this source of EMI and its characteristics need to be understood thoroughly for solving the associated EMI issues in the desired fashion. This thesis investigates EMI generation from pantograph arcing. The First phase of the work is based on experimental investigations and analyses conducted on a test setup which closely resembles pantographcontact wire interaction. Different possible mechanisms of the pantograph arcing and inuencing parameters like speed of the train, loadcurrent, voltage level, power factor etc. are identified. It was found that pantograph arcing is a polarity dependent phenomenon. It generates transients and asymmetrically distorted voltage and current waveforms. This in turn generates a net DC component and odd and even harmonics(up to order 10 was measured). In the second phase, different characteristics of these high frequency emission and inuencing parameters have been analyzed and presented. Presence of wideband high frequency components in the range from afew ten kHz to a few hundred MHz at measured current, electric and magnetic elds were confirmed. 10-90 % risetimes for current was measured from 5 ns to typically around 25 ns, whereas for electric field this is ranged from fraction of onens to 25 ns. Although there are variations, the rise times of the measuredtime domain waveform of current, electric and magnetic seems to have correlation with the higher frequency components. It was understood that major high frequency components measured could be from: (a) thearcing itself, (b) radiation from connected cables/wires, (c) resonance inthe associated circuits and (d) associated digital circuitry.This wideband electromagnetic emission causes interference in traction power, signalling and train control systems. Their possible propagation paths and consequences on different equipments are also elaborated.

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