Overhead line

Summary

An overhead line or overhead wire is an electrical cable that is used to transmit electrical energy to electric locomotives, trolleybuses or trams. The generic term used by the International Union of Railways for the technology is overhead line. It is known variously as overhead catenary, overhead contact line (OCL), overhead contact system (OCS), overhead equipment (OHE), overhead line equipment (OLE or OHLE), overhead lines (OHL), overhead wiring (OHW), traction wire, and trolley wire. An overhead line consists of one or more wires (or rails, particularly in tunnels) situated over rail tracks, raised to a high electrical potential by connection to feeder stations at regular intervals. The feeder stations are usually fed from a high-voltage electrical grid. Overview Electric trains that collect their current from overhead lines use a device such as a pantograph, bow collector or trolley pole. It presses against the underside of the lowest overhead wire, the contact wire.

Official source

https://en.wikipedia.org/wiki/Overhead_line

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On the contribution of the electromagnetic field components in field-to-transmission line interaction

Carlo Alberto Nucci

Based on the transmission line approximation, three different equivalent formulations have been proposed for evaluating the interaction between an external electromagnetic field and a transmission line. The difference among these 'coupling' formulations, which are summarized for the case of a lossless line, lies essentially in the representation of the source terms as a function of the external electromagnetic field components. In the paper we show that the contribution of a given electromagnetic field component is different depending on the particular adopted formulation. To show that, the three formulations are employed to calculate the voltages induced on an overhead line by a nearby lightning strike, and the contribution to the induced voltage of the various electromagnetic field components explicitly appearing in each formulation is emphasized. We conclude that it is misleading to speak about the contribution of a given electromagnetic field component to the total induced voltages without first specifying the coupling formulation one is using.

1995

Use of the full-wave finite element method for the numerical electromagnetic analysis of LEMP and its coupling with overhead lines

Carlo Alberto Nucci, Mario Paolone

The computation of lightning-originated surges on overhead power lines due to nearby lightning return strokes requires accurate models for the calculation of both the incident lightning electromagnetic pulse (LEMP) and the coupling of this field with the line conductors. The availability of numerical algorithms for the resolution of full-wave Maxwell's equations (also called numerical electromagnetic analysis - NEA) could provide benchmark results useful to assess the uncertainties introduced by approximate models and solution methods. Within this context, the paper presents and discusses the results of LEMP and lightning-induced voltages calculations obtained using a time-domain full-wave Finite Element Method (FEM) model. The results obtained by the FEM model are then compared with those provided by traditional approaches based, for the LEMP calculation, on the combined use of the dipole technique and the Cooray-Rubinstein formula and, for the LEMP-to-line coupling, on the Agrawal et al. model. © 2011 IEEE.

IEEE2011

The aim of this paper is to present the results of the performance study of medium voltage overhead distribution lines against lightning discharges, in the way to define methodologies to reduce the system failures. The results are obtained within the partnership among the High Voltage Laboratory of the Federal University of Itajubá, AES Sul Utility Company and the University of Bologna. The resultant performance is presented in terms of expected faults for 100 km of line for a density of discharges to the ground (GDF) of 1 discharge/km2/year. Commentaries on the relative performance and comparisons of different construction configurations of overhead lines are presented. ©2007 IEEE.

2007