Overhead Wires Research Articles

Energy Saving Potential of a Battery-Assisted Fleet of Trolley Buses

This article investigates the opportunities of integrating battery-assisted trolley buses into a given trolley bus network in public transportation. In this new generation of vehicles, the diesel-powered auxiliary unit is replaced with a high-performance traction battery. On the one hand, the new vehicles can be operated without the overhead wire, while on the other hand the battery capacity improves the overall system efficiency. The energy saving potential is identified via simulation of a realistic trolley bus line including the optimization of the energy management strategy. The problem is formulated as a convex optimal control problem. The results show that up to 20% of energy can be saved, compared to the case with conventional trolley buses only.

BEARING CAPACITY OF A HORIZONTALLY LOADED SINGLE PILE SUPPORT WITH SLEEPERS

The supports of a overhead wiring used in transport take up substantial loads both because of wires and constructions holding them and wind, dynamic and other extraordinary impacts. In case of using single-member piles a question about their stability appears. For this reason different sleepers constructions are used. In order to improve the bearing capacity of horizontally loaded single pile supports of the contact systems used in urban, road and rail transport, power lines, etc.., it is recommended to use sleepers as horizontally laid under the ground in the depth of support beams. The calculation methods for different support sleepers of different lengths and cross sections are not well investigated. The proposed calculation method allows determining the carrying capacity of horizontally loaded bearings with soil pieces of different structural dimensions and their location in the soil, which allows choosing the best option for cost and material consumption. The calculations offered by the authors prove the efficiency of sleepers use in order to increase the bearing capacity of horizontally loaded piles and the possibility to chose their size.

A new approach based on firefly algorithm for vision-based railway overhead inspection system

The maintenance of the pantograph–catenary system is a crucial problem in railway inspection systems. The quality of current collection depends on maintaining good contact between a moving pantograph and an overhead contact wire. Problems in the current collection system lead to the damage and disruption of railway traffic. Pantograph arcing occurs between the pantograph and the overhead wire because of the wear of the contact strip. This paper proposes an automatic inspection system for detecting the pantograph and arcs that occur using a firefly optimization algorithm. The proposed method is able to localize the pantograph as a rectangular region and detect the burst of arcing under different illumination and weather conditions simultaneously. The firefly algorithm based Otsu method is used to detect arcs that occur in this region. The proposed approach can serve as an automatic monitoring system and can detect the occurrence of arcing due to loss of contact. The proposed method was applied to four real pantograph videos and efficient results were obtained.

FDTD Computation of Lightning-Induced Voltages on Multiconductor Lines With Surge Arresters and Pole Transformers

In this paper, lightning-induced voltages on multiconductor lines with surge arresters and pole transformers have been computed using the 3-D finite-difference time-domain method. This method uses a subgrid model, in which spatial discretization is fine (cell side length is 0.5 m) in the vicinity of overhead wires and coarse (cell side length is 5 m) in the rest of the computational domain. In the simulations, four-conductor lines with surge arresters and pole transformers are considered. The 1-cm-radius overhead conductors are represented by placing a wire having an equivalent radius of about 0.12 m (≈ 0.23 × 0.5 m) in the center of an artificial rectangular prism having a cross-sectional area of 1 m × 1 m (2 cells × 2 cells) and the modified (relative to air) constitutive parameters: lower electric permittivity and higher magnetic permeability. The computed lightning-induced voltage waveforms agree reasonably well with the corresponding ones measured in the small-scale experiment of Piantini et al. (2007).

The Algorithm of Economically Beneficial Overhead Wires Cross Section Selection Using Corrected Transmission Lines Mathematical Models

The paper presents an unparalleled electric power system operating mode optimization algorithm aimed to economically beneficial overhead wires cross section selection with respect to electricity rate, electric power system elements price, reliability problem. The algorithm in question allows eliminating the limitation on the maximum allowable wires cross section with the help of corrected transmission lines mathematical models.

FDTD Simulations of Corona Effect on Lightning-Induced Voltages

In this paper, a simplified model of corona discharge for the finite-difference time-domain (FDTD) computations has been applied to analysis of lightning-induced voltages at different points along a 5-mm radius, 1-km long single overhead wire taking into account corona space charge around the wire. Both perfectly conducting and lossy ground cases were considered. FDTD computations were performed using a 3-D nonuniform grid. The progression of corona streamers from the wire is represented as the radial expansion of cylindrical weakly conducting (40 μS/m) region around the wire. The magnitudes of FDTD-computed lightning-induced voltages in the presence of corona discharge are larger than those computed without considering corona. The observed trend is in agreement with that reported by Nucci et al. and by Dragan et al ., although the increase predicted by our full-wave model (up to 5% and 9% for negative and positive lightning return strokes, respectively) is less significant than in their studies (up to a factor of 2) based on the distributed-circuit model with sources specified using the electromagnetic field theory. The disparity is likely to be related to the use of different charge-voltage diagrams, explicitly assumed by Nucci et al. and Dragan et al . and resulting from our FDTD model with corona in the present study. When corona is considered, there is a tendency for induced-voltage rise time to increase. It appears that the distributed impedance discontinuity, associated with the corona development on the wire, is the primary reason for higher induced-voltage peaks and longer voltage rise times, compared to the case without corona.

A Study of Surge Propagation Characteristics of Grounding Conductor using Approximate Formulas

The surge characteristics of a grounding conductor are quite different from those of an overhead wire. It is difficult to represent the characteristics of a grounding conductor in time domain without numerical simulation. This paper describes approximate formulas for voltage and current in a horizontal grounding conductor. The formulas are derived in time domain on the basis of the lattice diagram method, and are very simple. It is convenient from the engineer's point of view to do rough estimation of surge characteristics of a grounding conductor by the approximate formulas. Some empirical laws on the grounding have been employed without any discussions. The surge characteristics of a grounding conductor are discussed using the approximate formulas.

Computer Simulation of Aluminum Conductors Drawn in High Speed

Drawing speed is one important process in production over-head line, deform 3d software is used to simulate the drawing process. The distribution of stress-strain and temperature in different drawing speed with die angle and friction coefficient was investigated. The results shows that the aluminum conductors can be used in high speed drawing when die angle, drawing speed and frication coefficient of first pass is about11~13 degrees, 4~6m/s and 0.08~0.10 respectively, the uniformity of stress-strain and temperature is better for producing good quality over-head wires with high cold-drawing speed.

Corrosion Behavior of Aluminum Wire for Overhead Transmission Lines: Investigation and Analysis

SummaryThe corrosion behavior of aluminum wire used for overhead transmission lines was studied in four corrosion environments: (1) sodium chloride solution, (2) sodium chloride solution with addition of alumina particles, (3) aluminum chloride solution, (4) aluminum chloride solution with addition of alumina particles. The corrosion tests and polarization measurements revealed that environments 2 and 4 with alumina particles roughened and rapidly corroded the surface of the aluminum wire. It is considered that wet and dry environments of overhead transmission lines change aluminum hydroxide, present as a corrosion product, to alumina (aluminum oxide), which acts as an abrasive and weakens the surface of the aluminum wire. It is also shown that the corrosion of the aluminum wire occurs in an abrasive corrosion environment caused by alumina and corrosion fatigue due to vibration of the overhead wires. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 185(4): 18–24, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22486

Time and frequency characterization of radiated disturbance in telecommunication bands due to pantograph arcing

Radiated emissions from arcing between pantograph and overhead wire in electrical transportation systems extend up to the frequency bands currently used for telecommunications and may therefore affect quality of telecommunication systems. The paper investigates on the time and frequency characteristics of the disturbances. Transient amplitude, rise time and pulse duration were measured in the time domain to obtain the associated empirical distributions; the power spectrum and the frequency content were calculated in the bands of interest; finally a time–frequency representation has been used to observe the evolution of the power spectrum over time and determine the location of the main contributions. Measurement of the channel power has also been carried out to investigate on the relevance of the disturbance power for some bands of interest for telecommunication services.

A detachable mobile and adjustable telemetry system

Many traditional mobile telemetry systems require permanently mounting a rod through the cabin of a vehicle to serve as the mast for a directional antenna. In this article we present an alternative to this configuration by providing a platform that can be placed atop the vehicle in which the antenna mast can be mounted and controlled from the cabin of the vehicle. Thereby making this design a viable option for researchers who share vehicles with others that may not approve of permanent vehicle modifications such as placing a hole in the roof of the vehicle as required by traditional mobile configurations. We tested the precision and accuracy of detachable mobile and adjustable telemetry system (DMATS) in an urban park with varying terrain, tree stands, overhead wires, and other structures that can contribute to signal deflection. We placed three radiocollars 50 m apart and 1.2 m above the ground then established three testing stations ∼280 m from the location of the radiocollars. The DMATS platform required 12 h for completion and cost $1059 USD. Four technicians were randomly assigned radio collars to triangulate using DMATS and a handheld telemetry system. We used a one-way analysis of variance (ANOVA) with a Scheffe post hoc test to compare error ellipses between azimuths taken using DMATS and the hand held system. Average error ellipses for all testers was 1.96 ± 1.22 ha. No significant differences were found between error ellipses of testers (P = 0.292). Our design, the DMATS, does not require any vehicle modification; thereby, making this a viable option for researchers sharing vehicles with others that may not approve of permanent vehicle alterations.

Application of the TLM Method to Transient Simulations of a Conductor System With a Lossy Ground: Grounding Electrodes and an Overhead Wire

In this paper, we have applied the transmission-line modeling (TLM) method to analyzing transient responses of grounding electrodes and lightning-induced voltages on an overhead wire. In either analysis, a lossy ground was considered. TLM-computed responses agree reasonably well with the corresponding measured and finite-difference-time-domain-computed responses. This fact shows that the TLM method is effective and useful in analyzing lightning electromagnetic pulses and lightning-associated transient phenomena.

721 ちょう架式電車線のトロリ線の伝達マトリクス法による波動伝播解析(GS-10 振動(2))

721 ちょう架式電車線のトロリ線の伝達マトリクス法による波動伝播解析(GS-10 振動(2))

FDTD Simulation of Lightning Surges on Overhead Wires in the Presence of Corona Discharge

A simplified model of corona discharge for finite-difference time-domain (FDTD) computations has been applied to analyzing lightning surges propagating along overhead wires with corona discharge. The FDTD computations simulate the experiments of Inoue and Wagner . In Inoue's experiment, a 12.65-mm radius, 1.4-km-long overhead wire was employed, and in Wagner 's experiment, a 21- or 25-mm radius, 2.2-km-long overhead horizontal wire was employed. The critical electric field on the surface of the 12.65-mm-radius wire for corona initiation is set to E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> = 1.4, 2.4, or 2.9 MV/m, and those for 21- and 25-mm-radius wires are set to E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> = 2.2 and 2.1 MV/m, respectively. The critical background electric field for streamer propagation is set to E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cp</sub> = 0.5 MV/m for positive voltage application and E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cn</sub> = 1.5 MV/m for negative voltage application. The FDTD-computed waveforms (including wavefront distortion and attenuation at later times) of surge voltages at three different distances from the energized end of the wire agree reasonably well with the corresponding measured waveforms. Also, the FDTD-computed waveforms of surge voltages induced on a nearby parallel bundled conductor agree fairly well with the corresponding measured waveforms.

3-D FDTD Computation of Lightning-Induced Voltages on an Overhead Two-Wire Distribution Line

Lightning-induced voltages on a 738-m long overhead two-wire line have been computed using the 3-D finite-difference time-domain (3-D FDTD) method for solving Maxwell's equations. The 3-D FDTD method employed here uses a subgrid model, in which spatial discretization is fine (cell side length is 0.9 m) in the vicinity of overhead wires and coarse (cell side length is 4.5 m) in the rest of the computational domain. The overhead wires having radii of some millimeters are simulated by placing a wire having an equivalent radius of about 0.2 m (≈0.23 × 0.9 m) in the center of an artificial rectangular prism having a cross-sectional area of (2 × 0.9 m) × (2 × 0.9 m) and the modified (relative to air) constitutive parameters: lower electric permittivity and higher magnetic permeability. Induced-voltage peaks computed at different points along the line for the return-stroke speed of 130 m/μs and ground conductivity of 3.5 mS/m agree reasonably well with the corresponding voltage peaks measured in the rocket-triggered lightning experiment of Baker et al., in 1996.

Conservation insights from changing associations between habitat, territory distribution and mating system of Corn Buntings Emberiza calandra over a 20‐year population decline

Associations between habitat and animal distributions are widely used to make conservation recommendations. However, short‐term studies do not allow investigation of temporal variation in associations as habitats change or populations decline. Here we quantify changes in the habitat attributes and distribution of breeding territories in a multiple‐brooded, crop‐nesting farmland bird, the Corn Bunting Emberiza calandra, over a 20‐year period during which the study population declined by 91%. Corn Buntings were positively associated with weedy fields, overhead wires, spring cereals and, in early summer, with winter barley and forage grass. Territory associations with wires (positive) and fallow (positive in early summer, negative in late summer) were stronger in later years when the population was smaller. Trends in the proportions of males holding territories into late summer (decline), and mated polygynously or not at all (increases), suggested that habitat quality declined and became more spatially variable in later years. Field size increased and weed abundance within fields declined, reducing the availability of field‐boundary song‐posts, invertebrate‐rich foraging habitats and physical cover for nests within crops. Conservation recommendations are for weed‐rich or under‐sown spring cereals and winter barley combined with late‐cut hay and fallow, especially when offered close to song‐posts such as overhead wires. We also demonstrate the value of long‐term studies by comparing our 20‐year analysis with 3‐year periods at the start, middle and end of this period, and expose some risks of conservation recommendations derived from short studies.

A Simplified Model of Corona Discharge on Overhead Wire for FDTD Computations

A simplified model of corona discharge on overhead wire has been proposed for propagating surge computations using the finite-difference time-domain method. The radial progression of corona streamers from the wire is represented as the radial expansion of cylindrical conducting region whose conductivity is several tens of microsiemens per meter. Two wire radii are considered: 5 and 2 mm, in order to simulate two experimental con- figurations by Noda. The critical electric field on the surface of a 5-mm radius wire for corona initiation is set to E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> = 1.8 or 2.9 MV/m. For a 2-mm radius wire, it is set to E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> = 2.2 MV/m. The critical background electric field necessary for streamer propagation is set to E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cp</sub> = 0.5 MV/m for positive voltage application, and E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cn</sub> = 1.5 MV/m for negative voltage application. The computed waveform of radial current (including both conduction and displacement currents) agrees well with the corresponding measured waveform. Also, the computed relation between the total charge (charge residing on the wire and emanated corona charge) and applied voltage (qV curve) agrees well with the corresponding measured one, except for relatively low applied voltages. Additionally, the increase of coupling between the energized wire and another one nearby due to corona discharge is well reproduced.

Electromagnetic Field Coupling to Overhead Wire Configurations: Antenna Model versus Transmission Line Approach

The paper deals with two different approaches for the analysis of electromagnetic field coupling to finite length overhead wire: the wire antenna theory (AT) and the transmission line (TL) method. The analysis is carried out in the frequency and time domain, respectively. Within the frequency domain analysis the wire antenna formulation deals with the corresponding set of Pocklington integrodifferential equation, while the transmission line model uses the telegrapher's equations. The set of Pocklington equations is solved via the Galerkin-Bubnov scheme of the Indirect Boundary Element Method (GB-IBEM), while the telegrapher’s equations are treated using the chain matrix method and the modal equation to derive per-unit-length parameters. For the case of the time domain analysis AT model uses the space-time Hallen integral equation set, while TL approach deals with the time domain version of the telegrapher’s equations. Hallen equations are handled via time domain version of GB-IBEM, while time domain telegrapher’s equations are solved by using Finite Difference Time Domain (FDTD) method. Many illustrative computational examples for the frequency and time domain response, respectively, for several configurations of overhead wires, obtained via different approaches, are given in this paper.

Simulation of future global warming scenarios in rice paddies with an open-field warming facility

To simulate expected future global warming, hexagonal arrays of infrared heaters have previously been used to warm open-field canopies of upland crops such as wheat. Through the use of concrete-anchored posts, improved software, overhead wires, extensive grounding, and monitoring with a thermal camera, the technology was safely and reliably extended to paddy rice fields. The system maintained canopy temperature increases within 0.5°C of daytime and nighttime set-point differences of 1.3 and 2.7°C 67% of the time.

Modelling the magnetic field caused by a dc-electrified railway with linearly changing leakage currents

Magnetic fields produced by dc railways can disturb operations at geomagnetic observatories. These magnetic fields consist of two parts: the ideal “full-loop” field due to the traction current in an overhead wire and in the rails, and the “leakage” field due to currents leaking from the track into the ground. Pirjola et al. (2007) present formulas with numerical examples for the magnetic field assuming a constant leakage current density between the train and the feeding substation. Lowes (2009) considers this assumption questionable. In this paper, we derive exact formulas for the magnetic field assuming that the leakage current density changes linearly being largest at the train and decreasing to zero at the substation. The Earth is considered layered. Computer codes enable calculations of the magnetic fields due to any number and configuration of the train-substation pairs at any points of observation. Numerical examples show that the value of 10 pT can easily be exceeded. An important conclusion is that the magnetic fields in the cases of a linearly changing and a constant leakage current density do not differ much. Particular attention is paid to the temporal behaviour of the magnetic field when one or two trains travel along a railway.