1,721,073 research outputs found
Multiconductor transmission line models for PQ and EMC analysis of railway electrification systems
No full textThis paper present and discuss two methods that allows defining MTL models that allows to represent the railway power electrification systems with a reduced number of conductors. Groups of conductors shorted together are replaced with an equivalent conductor and group of conductors grounded are included into the reference conductor. Reducing criteria are developed in the frequency domain and their extension to the time domain is discussed. A section of the Italian 2x25 kV 50 Hz AC high speed railway power system is considered as a benchmark and reduction methods are applied to the MTL cells that represent this kind of electrification system, also including the high voltage grid that supply the Electrical Substation. The equivalent impedance at pantograph terminals and the disturbances on the track circuits caused by trains harmonic current injection are evaluated by using reduced models and taking into account several train positions along the railway line. The numerical results are reported, compared and discussed, considering both precision and computational times
Calculation of Rail Internal Impedance by using Finite Elements Methods and Complex Magnetic Permeability
No full textRail Internal Impedance Calculation by Using Finite Elements Method
No full textIn the present paper two new methods for the evaluation of the internal impedance of a rail are proposed. These methods are based on FEM and they consider different steel's magnetic behavior models. The first one is based on the normal magnetization curve and the equivalent sinusoid concept. In the second model, the hysteresis loops have been considered introducing the evaluation of complex magnetic permeability function. Rail's internal per unit length parameters are calculated in function of current and frequency. The results from FEM models are compared with the available measurements at the frequency of 50 Hz, and they are extended to other frequencies
Stray Current Effects Mitigation in Subway Tunnels
No full textThis paper brings an original contribution in the analysis of stray current and the evaluation of maximum potential in reference to particular transportation service conditions. Beginning with a real new transit system under construction in Italy, a finite element method analysis has been developed in order to propose precautionary measures to prevent the growth of anodic areas in reinforcement bars and to influence the design procedure for better environmental compatibility. A possible solution to respect the limits imposed by the international standards is presented. Real infield measurements with the aim to validate the data implemented in the model complete the study
Comparison of different physical models for PV power output prediction
Full text linkThe electricity produced from renewable energy, in particular from wind and photovoltaic plants, has seen exponential rise in the last decade. Consequently, the prediction of power produced from these plants is fundamental for the reliability, safety and stability of the grid. This paper compares three physical models describing the PV cell (corresponding to three-, four- and five-parameter equivalent electric circuit) and two thermal models for the cell temperature estimation (NOCT and Sandia). The models were calibrated and tested towards ten monocrystalline and eight polycrystalline modules installed at SolarTechLab at Politecnico di Milano. The hourly error of the forecasted power output is usually lower than 15Wh, while NMAE% and WMAE% are in the range of 0.5% and 10%. Low errors, calculated with actual weather conditions, suggest that the implemented models are accurate, but they cannot be directly compared with other approaches which adopt weather forecasts. Results show that there is no clear advantage of using complex models, but the data used for the model calibration mostly affect the model accuracy. It was found that forecasted power output are more accurate using experimental data and Sandia's thermal model in monocrystalline cells type, while for the polycrystalline the data from the manufacturer and NOCT have lower errors
Impact of High-Voltage Primary Supply Lines in the 2x25kV – 50 Hz Railway System on the Equivalent Impedance at Pantograph Terminals
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EMC Disturbances on Track Circuits in the 2x25kV High Speed AC Railways Systems
No full textThe High Speed/High Capacity railway lines uses the 2×25 kV - 50Hz power supply system that is supplied at high-voltage by dedicated lines that can be placed in close proximity to the railway line. The power system adopted for High Speed railway lines includes a lot of sources of disturbance and inject harmonic components in signaling circuits. This paper presents a detailed model for the railway system (including the primary line) with the aim to evaluate the noises affecting the track circuits as function of train position
Power Quality and Harmonic Analysis of End User Devices
No full textAmong the non-linear loads used in household, Compact Fluorescent Lamps (CFLs) and LED lamps are becoming more widespread, while incandescent lamps are intended to be replaced by these types of lighting devices. LEDs and CFLs are significantly more efficient and economical than incandescent lamps, and are expected to be used in 100% of residential lighting in the future. As nonlinear loads, LEDs and CFLs produce highly distorted currents. A large number of customers using LEDs or CFLs for domestic, commercial and industrial lighting could determine important Power Quality problems. The paper reports experimental measurement results regarding Power Quality in indoor lighting systems. The harmonic absorptions of several types of luminaries are analyzed, highlighting the impact behavior of different lamps function of used luminaries’ technologies. The recorded harmonic absorption allows characterizing the harmonic spectrum variability of the investigated lamps
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