Petter Nåvik

Dynamic assessment of existing soft catenary systems using modal analysis to explore higher train velocities: a case study of a Norwegian contact line system

Significant advances made on the rolling stock have considerably increased the possibility of higher speeds in existing railways. Thus, it is important to explore higher speeds and potential limiting factors of existing soft catenary systems. The present paper investigates procedures to assess the dynamic behaviour of these systems using response sampling and modal analysis. The assessment evaluates and quantifies dynamic response along the section. To verify the approach, a case study is conducted and the following assessment methods are used: lengthwise track correlation estimating dynamic predictability, power spectral density estimations before and after passage and short-time Fourier transforms and spectrograms. The combination provides detailed information on the dynamic behaviour. The first part introduces necessary considerations for suggested modal analysis. The second part describes an existing Norwegian section. The case study is conducted using a finite element model including a straight and a given section between Oslo-Trondheim, providing detailed evaluations and system limitation detections.

The use of dynamic response to evaluate and improve the optimization of existing soft railway catenary systems for higher speeds

An increasing demand for reduced travel times requires the exploitation of the full capacity of existing overhead railway catenary systems. This need has become an issue in Norway, as the majority of existing catenary systems are designed for a maximum speed of 130 km/h. In many regions, plans to reconstruct the railway line do not exist. Therefore, existing catenary sections must be optimized to increase a train’s velocity and reduce the total travel time. In this paper, the dynamic response is evaluated in an optimization investigation of an existing soft catenary system. A dynamic investigation that considers finite element models of existing soft railway catenary sections with original tension forces, current tension forces and suggested new tension forces for velocities at and above the design speed is conducted. The dynamic response is quantified by the interpretation of spectral densities and variations in their peak values. Due to more movement at mid-span than at the pole support, the effects from altering the tension forces and increasing the speed can be more accurately described and estimated by considering the dynamic content of the response at mid-span instead of the peak uplift at the pole support. A 23% increase in speed is possible for the system with the best tested new tension force setting, in which only the dynamic response and uplift at the pole support are considered.

Variation in predicting pantograph–catenary interaction contact forces, numerical simulations and field measurements

ABSTRACT The contact force between the pantograph and the contact wire ensures energy transfer between the two. Too small of a force leads to arching and unstable energy transfer, while too large of a force leads to unnecessary wear on both parts. Thus, obtaining the correct contact force is important for both field measurements and estimates using numerical analysis. The field contact force time series is derived from measurements performed by a self-propelled diagnostic vehicle containing overhead line recording equipment. The measurements are not sampled at the actual contact surface of the interaction but by force transducers beneath the collector strips. Methods exist for obtaining more realistic measurements by adding inertia and aerodynamic effects to the measurements. The variation in predicting the pantograph–catenary interaction contact force is studied in this paper by evaluating the effect of the force sampling location and the effects of signal processing such as filtering. A numerical model validated by field measurements is used to study these effects. First, this paper shows that the numerical model can reproduce a train passage with high accuracy. Second, this study introduces three different options for contact force predictions from numerical simulations. Third, this paper demonstrates that the standard deviation and the maximum and minimum values of the contact force are sensitive to a low-pass filter. For a specific case, an 80 Hz cut-off frequency is compared to a 20 Hz cut-off frequency, as required by EN 50317:2012; the results show an 11% increase in standard deviation, a 36% increase in the maximum value and a 19% decrease in the minimum value.

Wireless Monitoring of the Dynamic Behavior of Railway Catenary Systems

During the last couple of decades the railways have experienced a steady growth in high-speed rail. However, there still exist a considerable amount of infrastructure that is designed for older and completely different scenarios. This is also true when considering the power supply to the electric railways where a two level catenary system is commonly used. For the power supply to be reliable and uninterrupted under higher speeds there must be strict static and dynamic requirements. The current power supply systems for old electric railway lines, often called soft catenary systems, are characterized by their design for an optimal quasi-static behaviour. This paper primarily explores the behavior of the dynamic system using a newly developed monitoring system. This includes multiple wireless sensors mounted in arbitrary positions chosen to be beneficial in the description of the fundamental motions, and with a range above 700 m. However, for any monitoring scheme to be efficient, it is important to establish relevant dynamical system conditions and to verify existing systems behavior. This requires a full-scale instrumentation program and the associated system identifications. That is, for the railway catenary system it must be included several sensors measuring response at different points within one or several spans as well as close to the cantilevered supports. The system can then assess catenary response components such as uplift, frequencies, damping and mode shapes. In the current paper this is further explored using the location of Hovin station in Norway.

Uplift-Monitoring for Dynamic Assessment of Electrical Railway Contact Lines

Although international railways have seen a massive increase in high speed rail there are still large amounts of older existing infrastructure designed for completely different criteria. The current supply systems of old electric railway lines, called soft catenary systems, are characterized by their design towards an optimal quasi-static behaviour. To increase the speed it is important to explore possible limiting factors, i.e. to identify the dynamic consequences and limitations. This paper explores a newly developed sensor system. Several sensors are placed over approximately 150 m to capture the dynamic behaviour. This is then used to create a base line for future monitoring as well as for assessing the possibilities of increased speed. For soft contact lines it is important to control maximum uplift at the pole support and the dynamic behaviour. The stiffness of the system changes between poles as well as along the section depending especially on track geometry; this makes it equally important to assess several other points between pole supports. Excessive vibrations can produce loss of contact rendering arching, increased wear and disrupted power supply. In the present paper acceleration time series were used to predict maximum vertical displacement, train speed, to assess the dynamic behaviour and to quantify modal parameters.