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dc electrified traction systems are a potential source of stray currents. The purpose of this paper is to evaluate the harmful effects (electrolytic corrosion) that an electrified railway has on nearby earth return circuits (e.g. pipelines).

The electric circuit approach, based on the earth return circuit theory, to model stray currents interference on extended structures is presented. An exact method of calculation is applicable to any dc railway system in which tracks can be represented by a single earth-return circuit (equivalent rail) with current energization. In the approximate method, the equivalent rail with current energization is modeled as a large multinode electrical equivalent circuit with lumped parameters. The circuit is a chain of basic circuits, which are equivalents of homogenous sections of the rail. The electrode kinetics (polarization phenomenon) is taken into account in the model developed.

Formulas in partially closed forms are derived applicable to the analysis of currents and potentials along a pipeline laid in the proximity with railway tracks. The attempt is undertaken, to incorporate the electrode kinetics into the simulation model in which the polarization phenomenon (Tafel equation) is modeled by a non-linear voltage source with source voltage being iteratively calculated. The polarization potential along the affected pipeline can be determined.

The pipeline electrochemical response (polarization behavior – non-linear phenomenon on the interface metal-soil electrolyte) to the dc stray currents interference is innovative incorporated into the simulation model with lumped parameters using the iterative process.

The per-unit-length earth return mutual impedance of the overhead conductors plays an important role for analyzing electromagnetic transients or couplings of multi-conductor systems. It is impossible to have a closed-form expression to evaluate this kind of impedance. The purpose of this paper is to propose an efficient numerical approach to evaluate the earth return mutual impedance of the overhead conductors above horizontally multi-layered soils.

The expression of the earth return mutual impedance, which contains a complex highly oscillatory semi-infinite integral, is divided into two parts intentionally, i.e. the definite and the tail integral, respectively. The definite integral is calculated using the proposed moment functions after fitting the integrand into the piecewise cubic spline functions, and the tail integral is replaced by exponential integrals with newly developed asymptotic integrands.

The numerical examples show the proposed approach has a satisfactory accuracy for different parameter combinations. Compared to the direct quadrature approach, the computational time of the proposed approach is very competitive, especially, for the large horizontal distance and the low height of the conductors.

The advantage of the proposed approach is that the calculation of the highly oscillatory integral is completely avoided due to the fact that the moment function can be evaluated analytically. The contribution of the tail integral is well included by means of the exponential integral, though in an asymptotic way. The proposed approach is completely general, and can be applied to calculate the earth return mutual impedance of overhead conductors above a soil structure with an arbitrary number of horizontal layers.

The purpose of this paper is to present a mathematical model for studying the effects of the interconnection through bare‐buried conductors (BBC) of the secondary substations' earthing system of an urban area.

The developed methodology is based on three main points: the solution of the transmission lines' equations for the formulation of a lumped parameters model of a BBC considering the conductive effect; the division of the distribution network into simpler sub‐systems; and the calculation of all the voltages and currents of the medium voltage (MV) network and of the earthing systems using a multiport approach.

The methodology has been applied to various situations giving precious information on the behaviour of the earthing systems interconnected by means of BBC in presence of conductive effect. The results of the simulation allow to quantify the reduction of the dangerous voltages appearing during an earth fault, in presence of interconnection between the secondary substations' earthing systems, realized by means of BBC.

Some factors can influence the precision of the methodology. Indeed, for a correct simulation of the system it is necessary to know several electrical and geometrical parameters, among all the resistivity of the soil that, often, is known with a large degree of uncertainty.

Utilities are quite interested in this topic. The study of interconnected earthing systems in MV networks with the purpose of identifying safe extended areas named global earthing systems (GES) has important management and economic consequences.

The paper presents an original lumped parameters model of the BBC, able to simulate these elements with a high accuracy, also in presence of the conductive effect, and that can be easily included in the more general model of a distribution line, in order to perform the analytical study of the GES in MV networks. The model proposed allows one to overcome the limits of the application to the MV networks of similar models present in the literature for the study of the same topic in the high‐voltage networks.

The purpose of this paper is to present a method to calculate the transient induced voltages along the underground pipelines and analyze the transient interference generated in the pipelines due to the inductive coupling in the fault‐to‐ground condition of power lines in close proximity.

Based on finite difference‐time domain method, an improved method is proposed to calculate transient inductive interference in underground metallic pipelines due to a fault in nearby power lines. The frequency‐dependent problem in the analysis of transient interference is solved in phase domain. Compared with the traditional method, the disposal of phase‐modal transformation matrices’ frequency‐dependent characteristic is avoided and the calculation is simplified by using vector fitting approach and recursive algorithm greatly in the proposed method.

A novel improved method is proposed to calculate transient induced voltage distribution along underground metallic pipelines due to a fault in nearby power lines. Results show that the peak value of transient induced voltage at the most critical point is about 1.15 times of the magnitude in the steady state without the fault removed and the analysis of transient inductive interference is necessary in the fault‐to‐ground case of power lines.

In order to mitigate the interference from power lines to nearby pipelines, pipelines should be good grounded and positioned as far away from the power line as possible. In high soil resistivity areas, the common corridor should be avoided.

The paper presents a method to calculate the transient induced voltages along the underground pipelines and analyze the transient interference generated in the pipelines due to the inductive coupling in the fault‐to‐ground condition of nearby power lines. The proposed method is general and can also be applied to other transient interference studies such as crosstalk problems of communication networks and interference between power lines and aboveground pipelines or communication cables. Effects of various parameters upon the inductive interference generated in underground pipelines due to a fault in nearby power lines are analyzed to be a guide for controlling the inductive interference.

The coating, printing and bonding of both single and multi‐layer paper, plastic, foil, and tin‐plate products can be a complex process. Creating an environment where adhesives, inks or substrate materials will adhere successfully to each other, demands that certain essential parameters are fulfilled. Two examples serve to highlight these; the printing of ink onto a metallised or foil surface, such as is commonly used in the food packaging industry, and the application of plastic materials onto coated paper substrates, as found in the manufacture of photographic printing papers. In the first example, ink must adhere and dry quickly and evenly to prevent lift‐off and scuffing. In the second example, the coated paper must be prepared so that it bonds immediately in accordance with pre‐determined process parameters, to prevent the future separation or delamination of individual layers. In both examples, the base material must be smooth and clean, exhibiting a neutral electrical status, in order to make effective product adhesion and ultimately product presentation possible,

A technique for studying the propagation of surges on lines in the presence of corona and a lossy earth is presented. Each line section is modelled by lumped circuit components representing corona and earth effects. The component values are readily obtained from theoretical and experimental investigations. The circuit is solved in the time domain using transmission line modelling (TLM). The results show good agreement with other experimental and theoretical investigations.

The purpose of this paper is to define a new methodology for studying interconnected earthing system inside unearthed medium voltage (MV) networks.

The developed methodology is based on the division of the MV network into simpler sub‐systems and its resolution using a multiport approach.

The methodology has been applied to various situations giving precious information on the behaviour of the interconnected earthing systems. The comparison between the results of the simulations and measurements done on a really existing network has shown that the methodology is able to provide accurate results.

Some factors can influence the precision of the methodology. Indeed, for a correct simulation of the system it is necessary to know several electrical and geometrical parameters, often obtainable with difficulty.

Utilities are quite interested in this topic. The study of interconnected earthing systems in MV networks with the purpose of identifying safe extended areas named Global Earthing Systems has important management and economic consequences.

The paper presents a new analysis methodology applicable to MV networks that surpasses the limits of the analysis methodology generally applied for the study of the same topic in high voltage networks.

To provide an efficient interconnection system, compromises must be made on materials and packing density within acceptable limits, and designers must understand electrical characteristics and the functioning of signal generating devices. High speed digital logic devices are analysed with special attention given to signal swings. Solutions to the problem of line reflection currents are suggested, and the decoupling process is explained. Board design is vitally important and the power and earth distribution contribute strongly towards its success or failure. Power distribution on double‐sided boards is examined, with a consideration of various arrangements of capacitors used for decoupling. After discussion of the effects of other tracks, it is evident that signal tracking lengths should be kept to a minimum, while line impedances are maximised. Guidelines for efficient tracking are provided and an explanation of the trackability factor of a PCB reveals power distribution past the ends of packages to be the most effective arrangement for achieving high packing densities. Double‐sided boards should be used where possible in preference to multilayers.

THE forbearance of readers is requested at the outset for a personal note, considered to be inseparable from the basic purpose of this paper. The author's professional duties for many years prior to this war were concentrated on the specialist work of the design of distribution and transmission networks of various electricity supply undertakings, covering the main development period of electricity supply in this country, and also including the change‐over of direct current consumers to alternating supply. The author was directed for the period of the war into the aircraft industry and again specialized on the electrical side, and the similarity of the technical problems which have arisen in both his experiences leave no doubt that aircraft electrical systems can benefit from the hard‐won success of the electricity undertakings, whose achievements and mistakes alike are given publicity and opportunity for discussion. The technical success of supply systems is generally admitted to be in a large measure due to the freely‐pooled contributions from the experience of engineers in the profession. The author airs very decided personal views, many of them contrary to present practice and forecasts, and in order that the criticism it is hoped to arouse should not be marred by any misunderstandings, it is made clear that his experience is limited to British aircraft; with no knowledge of American practice. The scope of electrical applications in aircraft is very great and it does seem that as each new application arises, those responsible endeavour to design suitable systems and apparatus de novo instead of ascertaining first whether or no there is a similar application in the electrical industry which has been tried out over the years, and which if applied with suitable modification to aircraft would cut out the inexcusable “teething” troubles. For example, the risk of fire being carried along by cables has been very thoroughly studied in switching stations; the deleterious effects of oil upon rubber insulation were appreciated years ago; and telephonic intercommunication has been utilized always in generating stations where the noise is quite equal to that which obtains in aircraft; also the practice of endeavouring to classify cables by their current carrying capacities was abandoned a very long time ago. These are only a few examples in which the author feels that aircraft electrical systems can be improved as a result of experience in the allied industry.

As commercial and military aircraft continue to be subject to direct lightning flashes, there is a great need to characterize correctly the electrical currents and electric potential fluctuations on an aircraft to determine alternative design approaches to minimizing the severity of the lightning-aircraft dynamics. Moreover, with the increased severity of thunderstorms due to global warming, the need arises even more to predict and quantify electrical characteristics of the lightning-aircraft electrodynamics, which is normally not measurable, using a reliable electric model of the aircraft. Such a model is advanced here. The paper aims to discuss these issues.

The case considered in this paper is that of an aircraft directly attached to an earth flash lightning channel. The paper develops a new approach to modelling the aircraft using electric dipoles. The model has the power to represent sharp edges such as wings, tail ends and radome for any aircraft with different dimensions by using a number of different sized dipoles. The distributed transmission line model (TLM) of the lightning return stroke incorporating the distributed aircraft model is used to determine aircraft electrical elements and finally the electric current induced on the aircraft body due to lightning's interaction with the aircraft. The model is validated by the waveform method and experimental results.

The dipole model proposed is a very powerful tool for minute representation of the different shapes of aircraft frame and to determine the best geometrical shape and fuselage material to reduce electric stress. This charge simulation method costs less computer storage and faster computing time.

The paper for the first time presents a computer-based simulation tool that allows scientists and engineers to study the dynamics of voltage and current along the aircraft surface when the aircraft is attached to a cloud to ground lightning channel.