Dynamic behaviour of existing and new railway catenary systems under Norwegian conditions

Abstract

This thesis concerns the dynamic behaviour of railway catenary systems, particularly Norwegian systems. The aim of this PhD study is to increase the knowledge of the dynamic behaviour of these systems. This includes analyses of field measurements sampled during daily train operation and parameter studies by developing and using a detailed and validated numerical model. A range of field measurements was obtained and analysed during the study. These include displacements, accelerations, rotational velocities, contact forces and geometries. A new and purposespecific wireless monitoring system designed for field measurements was developed during the thesis and was used for sampling accelerations and rotational velocities. The monitoring system consists of up to ten wireless sensors and one master unit. The sensors can be mounted arbitrarily over a range of 1400 m. Triggering is mainly accomplished by passing trains, but manual triggering is made possible. Time synchronization of the sensors is ensured by a developed scheme. Furthermore, closerange photogrammetry and integrated accelerations were used to estimate and verify the displacement uplift time series. The analysed recorded contact forces were obtained from a database constructed by data from an overhead line recording locomotive. In addition, catenary geometry was measured by laser. The study develops, presents and uses different methods for assessing the dynamic behaviour of railway catenary systems by evaluating both numerical simulations and field measurements. The methods include the use of power spectral density (PSD), short-time Fourier transforms (STFT), covariance-driven stochastic subspace method (Cov-SSI), histograms, cross-correlation and extreme value probability distributions. The thesis demonstrates that the dynamic behaviour of railway catenary systems has a high grade of variability. This includes high variability in the frequency content that is shown to be substantially dependent on the position in a span, the properties of the span, the properties of each catenary section and the loading. This demonstrates the importance of establishing system frequencies and positionspecific frequencies. The variability of the loading depends on the train speed, static uplift, type of pantograph and wear on pan heads. This makes it favourable to perform both overall analyses, including many train passages, and analyses of single train passages to obtain the full picture. In addition, the importance of the variability in the response at one point in the catenary during a train passage is demonstrated and requires that the analysis should be performed both for segments of the time series and for the whole time series. The study clearly suggests distinguishing pre- and post passage parts based on their difference in frequency content. In addition, clear differences found in the lateral and vertical response indicate that both should be included in a frequency investigation to improve interpretations. The dynamic response was demonstrated to be a good tool for parameter study. It was used to evaluate changes in tension forces, the effect of rapid changes in contact wire height and differences depending on curvature. A damping study including analysis of data from three different catenary sections and several train passages resulted in proposed Rayleigh damping coefficients for numerical models. Above all, this study highlights the complexity of the pantograph–catenary interaction.