doktorska disertacija
Anton Habjanič (Author), Mladen Trlep (Mentor), Jože Pihler (Co-mentor)

Abstract

Odziv ozemljitvenega sistema, v katerega se razelektri visok tokovni oziroma napetostni udarni val, kot je na primer udar strele, tok kratkega stika ali paprenapetost zaradi stikalne manipulacije, se znatno razlikuje od odziva v primeru nizkih frekvenc in enosmernih razmer, saj induktivni karakter postane glede na uporovnega vse bolj pomemben, razen tega pa veliki tokovi oziroma visoke napetosti lahko povzročijo tudi ionizacijo zemljišča. Zato je za pravilno načrtovanje ozemljitvenega sistema bistvenega pomena imeti na razpolago ustrezno programsko orodje za simulacijo oziroma napovedovanje lastnosti ozemljitvenega sistema v času prehodnega pojava. V ta namen je bila v preteklosti na podlagi praktičnih preskusov razvita cela množica izkustvenih enačb ter analitičnih in numeričnih metod, s katerimi je mogoče predvideti obnašanje ozemljitvenega sistema. Ob tem pa je potrebno poudariti, da povečini te študije prinašajo realne rezultate le v primeru zelo enostavnih geometrij ozemljil oziroma nizkih amplitud tokovnih in napetostnih udarnih valov, medtem ko v primeru analize kompleksnejših ozemljitvenih sistemov oziroma v primeru, ko je potrebno upoštevati tudi ionizacijo zemljišča okrog vodnikov ozemljitvenega sistema, večinoma ne držijo. Problem je lahko na učinkovit način rešljiv z numeričnim modeliranjem na osnovi metode končnih elementov (MKE), kar je opisano v doktorski disertaciji, kjer je vključena tudi analiza vplivov dodatne ozemljitvene substance in strukture zemlje na lastnosti ozemljitvenega sistema. Za verifikacijo novih programskih rešitev pa je v doktorski disertaciji opravljena še primerjava dobljenih numeričnih rezultatov z rezultati meritev in simulacij iz literature. Glavni namen doktorske disertacije je torej razviti ustrezno programsko rešitev za implementacijo novega principa numeričnega modeliranja časovno odvisnega odziva ozemljitvenega sistema, v katerem, za razliko od do sedaj uveljavljenega pristopa na osnovi MKE v frekvenčnem področju, poteka reševanje diferencialnih enačb elektromagnetnega polja z uporabo MKE direktno v časovnem področju.

Keywords

ozemljitveni sistemi;časovno odvisno elektromagnetno polje;numerični modeli;metoda končnih elementov;ionizacija zemljišča;

Data

Language: Slovenian
Year of publishing:
Source: Maribor
Typology: 2.08 - Doctoral Dissertation
Organization: UM FERI - Faculty of Electrical Engineering and Computer Science
Publisher: [A. Habjanič]
UDC: 621.316.99:519.61/.64(043.3)
COBISS: 12289046 Link will open in a new window
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Other data

Secondary language: English
Secondary title: Numerical model of transient electromagnetic field around the grounding system by the finite element method
Secondary abstract: The behaviour of a grounding system excited by high impulse current or voltage(such as lightning stroke, short circuit current or overvoltage due to the switching manipulation) considerably differs from that at low-frequency and at direct conditions. Namely, inductive character can become more and more important with respect to resistive character and, in addition, large currents or high voltages can also generate soil ionization. In order to obtain a correct design of a grounding system, it is fundamental to possess an appropriate software package (calculation code) which is able to simulate or to predict the impulse characteristics of a grounding system. For this reason, on the basis of practical experiments, many empirical formulas and analytical or numerical methods to predict the behaviour of a grounding system have been developed in the past. Furthermore, it has to be mentioned that most of these studies produce realistic results only for very simple electrodes or for impulse currents and voltages having small amplitudes but, in general, they fail when complex grounding systems have to be analysed or when soil ionisation surrounding the conductors of a grounding system occurs (i.e., when a grounding system is excited by high impulse currents or voltages). An efficient solution to this problem may be obtained by numerical modelling based on the finite elements method (FEM) as it has been described in the thesis where also the analysis of the additional substance's and the soil's structure influences on the characteristics of a grounding system has been included. For the verification of the new program solutions a comparison of the obtained numerical results both with experimental tests and with the simulations found in the literature has also been performed in the thesis. Accordingly, the main goal of the thesis has been to develop a proper program solution for the implementation of the new methodology of numerical modelling of the transient behaviour of a grounding system. In contrast to recently known procedure based on FEM in frequency domain, in this new methodology for the first time the differential equations of the electromagnetic field have been solved using the FEM directly in time domain.
Secondary keywords: grounding systems;transient electromagnetic field;numerical models;finite element method;soil ionization;Ozemljitveni sistemi;Disertacije;Elektromagnetno polje;
URN: URN:SI:UM:
Type (COBISS): Dissertation
Thesis comment: Univ. Maribor, Fak. za elektrotehniko, računalništvo in informatiko
Pages: 112 str.
Keywords (UDC): applied sciences;medicine;technology;uporabne znanosti;medicina;tehnika;engineering;technology in general;inženirstvo;tehnologija na splošno;mechanical engineering in general;nuclear technology;electrical engineering;machinery;strojništvo;electrical engineering;elektrotehnika;mathematics;natural sciences;naravoslovne vede;matematika;mathematics;matematika;computational mathematics;numerical analysis;računska matematika;numerična analiza;
ID: 13608