The Electrical Behaviour of Railway Pantograph Arcs

Abstract

Electric arcing is an unavoidable consequence of the current collection process by sliding contact in railways and metros, and in general in many electrified transportation systems (ETSs). The most relevant consequences in an electrical perspective are: the occurrence of transients triggering resonant behaviour and transient responses, reduction of the energy efficiency of the system, conducted and radiated disturbance, in particular for the new radio systems widely employed for signalling and communication. The involved parameters are many (type of materials, current intensity, DC and AC supply, relative speed, temperature), as well as the studied characteristics (arc instability and lifetime, dynamic behaviour, electrical system response, radiation efficiency and coupling to external radio systems). This work reports the state of the art in arc modelling, arcing experimental characterisation, interaction with the supply system, radiated emissions and disturbance to radio systems, providing a complete description of phenomena and of reference data, critically discussing similarity and differences between sources. Proposed arc models are many with different assumptions and simplifications for various applications, so that a critical review and discussion are a necessity, considering the many different approaches and not-so-obvious applicability. The comparison with experimental results highlights unavoidable discrepancies, also because of intrinsic arc variability and for the many involved parameters and operating conditions. The impact of the arc as embedded in the railway system is then considered, speaking of conducted and radiated phenomena, including interference to radio communication systems and arc detection. The most prominent effect for conducted emissions is the excitation of system resonances, including the LC filters onboard rolling stock and substations in DC railways, with consequences for disturbance and energy efficiency, and this is discussed in detail. Conversely, for high frequency emissions, the attenuation along the line circuit is significant and the effective distance of propagation is limited; nevertheless radiated electromagnetic field emissions are a relevant source of disturbance for radio systems within the ETS premises and outside (e.g., at airports). The published approaches to quantify performance reduction are discussed with emphasis on experimental methods.

Extended Pantograph–Catenary Arc Modeling and an Analysis of the Vehicular-Grounding Electromagnetic Transients of Electric Multiple Units

“…The TB voltages and currents were investigated in various grounding layouts and resistances and compared, focusing on different PC arcing scenarios [21]. A supercapacitor-based method was proposed to mitigate the over-voltage from the PC arcing and its effectiveness was verified by simulations [22]. However, transient over-voltages to vehicular grounding were not scrutinized in this scenario.…”

Review of Waveform Distortion Interactions Assessment in Railway Power Systems

“…Moreover, the authors of [9] present a review of different characterization methods for the impedance of catenary lines for resonance studies, offering an analysis on the influence of the methods used in calculations for a real 25 kV catenary scheme. Other review papers cover some power quality or electromagnetic compatibility aspects of railway systems that can correlate with waveform distortion issues like low-frequency oscillation [10], the impact of space and weather [11], human exposure to low-frequency electromagnetic fields [3], pantograph arcs [12], radiated electromagnetic emission measurements [13], etc.…”