THE INFLUENCE OF CONDUCTIVE PASSIVE PARTS ON THE MAGNETIC FLUX DENSITY PRODUCED BY OVERHEAD POWER LINES

There has been apprehension about the possible adverse health effects resulting from exposure to power frequency magnetic field, especially in the overhead power lines vicinity. Research work on the biological effects of magnetic field has been substantial in recent decades. Various international regulations and safety guidelines, aimed at the protection of human beings, have been issued. Numerous measurements are performed and different numerical algorithms for computation of the magnetic field, based on the Biot-Savart law, are developed. In this paper, a previously developed 3D quasistatic numerical algorithm for computation of the magnetic field (i.e. magnetic flux density) produced by overhead power lines has been improved in such a way that cylindrical segments of passive conductors are also taken into account. These segments of passive conductors form the conductive passive contours, which can be natural or equivalent, and they substitute conductive passive parts of the overhead power lines and towers. Although, their influence on the magnetic flux density distribution and on the total effective values of magnetic flux density is small, it is quantified in a numerical example, based on a theoretical background that was developed and presented in this paper

2D BEM analysis of power cables thermal field

This paper describes a novel 2D BEM numerical model for analyzing buried power cables thermal field. The total number of power cables and homogeneous subdomains inside the cable trench are completely arbitrary. A novelty in this paper is that a part of unbounded external boundary (earth surface) has been modelled using a new type of boundary elements named infinite boundary elements. Besides, the efficiency of the numerical method developed is based on successful application of analytical integration along linear boundary elements and infinite boundary elements. Using double and multiple global node technique, the correct numerical approximation of the normal flux density at the points with its physical discontinuity has been made possible. Illustrative numerical examples with known analytical solutions are solved

Computation of Carson formulas using piecewise approximation of kernel function

Novel approach for the high-accurate computation of Carson formulas is presented. Carson formulas are used for computation of per-unit length (pul) self and mutual impedances of infinitely long parallel conductors. Numerical algorithm described in this paper uses a piecewise approximation of the kernel function which appears in the Carson formula corrections. Approximated kernel function is multiplied by the rest of the integrands in the impedance correction expressions and analytically integrated. By using the proposed algorithm, highaccurate results with the desired computed n-digit accuracy can easily be obtained. Results computed by the proposed algorithm are compared with the two most commonly used approximation methods for large frequency range

COMPUTATION OF PER-UNIT-LENGTH INTERNAL IMPEDANCE OF A MULTILAYER CYLINDRICAL CONDUCTOR WITH POSSIBLE DIELECTRIC LAYERS

In this manuscript, a novel method for computation of per-unit-length internal impedance of a cylindrical multilayer conductor with conductive and dielectric layers is presented in detail. In addition to this, formulas for computation of electric and magnetic field distribution throughout the entire multilayer conductor (including dielectric layers) have been derived. The presented formulas for electric and magnetic field in conductive layers have been directly derived from Maxwell equations using modified Bessel functions. However, electric and magnetic field in dielectric layers has been computed indirectly from the electric and magnetic fields in contiguous conductive layers which reduces the total number of unknowns in the system of equations. Displacement currents have been disregarded in both conductive and dielectric layers. This is justifiable if the conductive layers are good conductors. The validity of introducing these approximations is tested in the paper versus a model that takes into account displacement currents in all types of layers

Dangerous Voltages due to Direct Lightning Strike into the Communication Tower

This paper presents a novel technique for computing dangerous voltages due to direct lightning strike into the communication tower and associated earthing system, which is based on the use of the well-known ATP-EMTP software package. The earthing grid and the communication tower structure are approximated by the circular cross section conductors. In numerical model, conductors are subdivided into segments (1D finite elements) and Clark's model with distributed constant parameters is then applied. Because of the limitations of ATP-EMTP software package, the leakage resistance of buried segments is modelled as additional lumped parameter. Analytical expressions for distributed and lumped segment parameters are derived using the average potential method. Mutual electromagnetic coupling between segments is neglected due to the limitations imposed by the ATP-EMTP software package, which is based on transmission line approach. Separate computer program is developed for obtaining the earth surface transient potential distribution, from which step and touch voltages are then computed

A hybrid algorithm for computation of rectangular conductor internal impedance

U radu je razvijen hibridni algoritam za proračun unutarnje impedancije po jedinici duljine pravokutnog vodiča. Do izabrane granične frekvencije vrijednost unutarnje impedancije računa se primjenom dvodimenzionalne analitičke Giacolettove formule. Za te frekvencije, Giacolettova beskonačna suma može se dovoljno dobro aproksimirati sa prvih 150 članova. Pokazano je da se za veće vrijednosti frekvencije pravokutni vodič može dovoljno točno aproksimirati pomoću cilindričnog vodiča. Predloženi hibridni algoritam, za više frekvencije, daje točnije rezultate u kratkom računskom vremenu u odnosu na Giacollettovu formulu aproksimiranu s manjim brojem članova beskonačne sume.A hybrid algorithm for the computation of rectangular conductor per unit length internal impedance is developed. Up to a switching frequency, the internal impedance is computed using a two-dimensional analytical formula developed by Giacoletto. For these frequencies, 150 terms of Giacoletto infinite sum give a sufficiently good approximation. For higher frequencies, it is shown that the rectangular conductor can be quite accurately approximated by a cylindrical conductor. The proposed hybrid algorithm, for higher frequencies, features improved accuracy and speed when compared to the Giacoletto formula truncated after a small number of terms

A hybrid algorithm for computation of rectangular conductor internal impedance

U radu je razvijen hibridni algoritam za proračun unutarnje impedancije po jedinici duljine pravokutnog vodiča. Do izabrane granične frekvencije vrijednost unutarnje impedancije računa se primjenom dvodimenzionalne analitičke Giacolettove formule. Za te frekvencije, Giacolettova beskonačna suma može se dovoljno dobro aproksimirati sa prvih 150 članova. Pokazano je da se za veće vrijednosti frekvencije pravokutni vodič može dovoljno točno aproksimirati pomoću cilindričnog vodiča. Predloženi hibridni algoritam, za više frekvencije, daje točnije rezultate u kratkom računskom vremenu u odnosu na Giacollettovu formulu aproksimiranu s manjim brojem članova beskonačne sume.A hybrid algorithm for the computation of rectangular conductor per unit length internal impedance is developed. Up to a switching frequency, the internal impedance is computed using a two-dimensional analytical formula developed by Giacoletto. For these frequencies, 150 terms of Giacoletto infinite sum give a sufficiently good approximation. For higher frequencies, it is shown that the rectangular conductor can be quite accurately approximated by a cylindrical conductor. The proposed hybrid algorithm, for higher frequencies, features improved accuracy and speed when compared to the Giacoletto formula truncated after a small number of terms

2D BEM analysis of power cables thermal field

This paper describes a novel 2D BEM numerical model for analyzing buried power cables thermal field. The total number of power cables and homogeneous subdomains inside the cable trench are completely arbitrary. A novelty in this paper is that a part of unbounded external boundary (earth surface) has been modelled using a new type of boundary elements named infinite boundary elements. Besides, the efficiency of the numerical method developed is based on successful application of analytical integration along linear boundary elements and infinite boundary elements. Using double and multiple global node technique, the correct numerical approximation of the normal flux density at the points with its physical discontinuity has been made possible. Illustrative numerical examples with known analytical solutions are solved