Detection of Harmonic Overvoltage and Resonance in AC Railways Using Measured Pantograph Electrical Quantities

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.

Section: Excitation Of Line Resonancesmentioning

confidence: 99%

mentioning

confidence: 99%

The Electrical Behaviour of Railway Pantograph Arcs

Mariscotti

2023

“…Assessments of rolling stock distortions are carried out for several reasons: traditionally, compliance to limits of emission to prevent interference to signalling [29,30], and in general, excessive induction [31,32]; more recently, attention has been placed on power quality with respect to the rest of the network [33], to resonance triggering and consequential overvoltages [28,34,35]. Finally, distortion has implications for power and energy consumption [36][37][38]; this is gathering more attention, i.e., in order to improve the energy efficiency of electrified transportation systems [39] in a sustainability perspective.…”

Section: Ac Railway System and Electrical Quantitiesmentioning

confidence: 99%

Non-Intrusive Load Monitoring Applied to AC Railways

Mariscotti

2022

Self Cite

Non-intrusive load monitoring takes place in residential and industrial contexts to disaggregate and identify loads connected to a distribution grid. This work studies the applicability and effectiveness for AC railways, considering the highly dynamic behavior of rolling stock as an electric load, immersed in varying contexts of moving loads. Both voltage–current diagrams and harmonic spectra were considered for identification and extraction of features relevant to classification and clustering. Principal components were extracted, approaching the problem using principal component analysis (PCA) and partial least square regression (PLSR). Clustering methods were then discussed, verifying separability performance and applicability to the railway context, checking the performance by means of the balanced accuracy index. Based on more than one hundred measured spectra, PLSR has been confirmed with superior performance and lower complexity. Independent verification based on dispersion and correlation were used to spot relevant spectrum components to use as clustering features and confirm the PLSR outcome.

“…As the overhead contact line system suffers multiple impacts from the pantograph [2], wind load [3][4][5][6], vehicle-track perturbations [7][8][9][10][11], electric shocks [12], temperature variance [13][14][15] and some other types of disturbances [16,17], almost all the rail operators have widely recognised the overhead contact line as the most vulnerable part in the traction power system [18]. Therefore, the dynamics of the overhead contact line and the pantograph have attracted ever-increasing attention from many scholars.…”

Section: Literature Reviewmentioning

confidence: 99%

Effect of Overhead Contact Line Pre-Sag on the Interaction Performance with a Pantograph in Electrified Railways

Mei

Song

2022

In the high-speed rail industry, the overhead contact line erected along the railroad is used to supply the electricity to the high-speed train via a pantograph on the carbody’s roof. This work attempts to explore the effect of contact line pre-sag on the contact quality between the pantograph and the contact line. A nonlinear finite element approach is implemented to build the overhead contact line system with accurate description of the pre-sag of the contact line. Through a nonlinear solution, the effect of contact line pre-sag on the contact force is analysed with different train speeds and tension classes. The analysis result indicates the feasibility of tuning the pre-sag to improve the interaction performance at a given speed and tension class. In the low-speed range, the change of pre-sag does not have a significant effect on the interaction performance. However, when the speed increases up to a certain value, the effect of pre-sag on the contact force is nonnegligible. The increase in tension can reduce the sensitivity of the interaction performance to the pre-sag. An optimisation procedure is implemented to obtain the optimal amount of pre-sag for different train speeds and tension classes. The results indicate a necessity to include a certain amount of contact line pre-sag to maintain an excellent interaction performance at high speed.