Knjiga Napajanje elektricne vuce obrađuje osnovnu problematiku sustava napajanja elektrificiranih... more Knjiga Napajanje elektricne vuce obrađuje osnovnu problematiku sustava napajanja elektrificiranih pruga. Namijenjena je studentima na diplomskom i poslijediplomskom sveucilisnom studiju koji izucavaju građu vezanu uz elektricne željeznice. Može biti korisna i mnogim strucnjacima koji se na bilo koji nacin bave tim problemima u praksi.
Studija je provjerila mogucnosti prikljucka 6 novih EVP-a za napajanje nove željeznicke pruge na ... more Studija je provjerila mogucnosti prikljucka 6 novih EVP-a za napajanje nove željeznicke pruge na prijenosnu elektroenergetsku mrežu s razlicitih aspekata. U predmetnoj studiji pokusalo se sto realnije sagledati stvarne mogucnosti razvoja prijenosne mreže, te definirati minimalne zahtjeve za izgradnjom novih prijenosnih objekata neophodnih za sigurno napajanje novih EVP-a, vodeci pri tom racuna da se postojecim potrosacima ne narusi pouzdano napajanje kvalitetnom elektricnom energijom. Buduci da je rijec o prikljucku nesimetricnih potrosaca na prijenosnu mrežu, svi proracuni tokova snaga i analize sigurnosti N-1 provedeni su programskim paketom za trofazni proracun tokova snaga. Proracuni su provedeni uz uvažavanje stvarnog nacina prikljucka postojecih EVP-a na prijenosnu mrežu i njihovog planiranog porasta opterecenja u promatranom periodu do nazivne 2016., odnosno 2020. godine. Na taj je nacin omoguceno cjelovito sagledavanje problematike naponskih i strujnih nesimetrija, sto je u skladu s Mrežnim pravilima HOPS-a. Osim navedenih proracuna tokova snaga i analiza sigurnosti N-1, provedeni su i proracuni maksimalnih i minimalnih struja trofaznog, jednofaznog i dvofaznog kratkog spoja. Proracuni su provedeni prema međunarodnom standardu IEC 60909. Rezultati proracuna maksimalnih struja kratkog spoja koristeni su za provjeru dimenzioniranja postojece i nove rasklopne opreme u prijenosnoj mreži, dok su rezultati proracuna minimalnih struja kratkog spoja koristeni za procjenu varijacija napona i razine emisije flikera, te visih harmonika uslijed prikljucka novih EVP-a.
The paper discusses the issue of skin effect impact on the current distribution or on the current... more The paper discusses the issue of skin effect impact on the current distribution or on the current density over the conductor cross-section The consequence of the skin effect, which drives the current towards the conductor surface, is an uneven current distribution over the conductor cross-section. A mathematical algorithm is presented enebling the determination of the current density distribution over the tube conductor cross-section. The algorithm is computed with the Maxwell's equation from the theory of electromagnetic fields and by using Bessel's functions of the first and second order. With thus implemented model the authors developed an algorithm for the current density determination with consideration of the skin effect impact on the multi-layer bare conductor for overhead power transmission lines of the ACSR 490/65 type. Results are given for the current density distribution over individual layers of the observed conductor (the steel core and three conductive aluminum layers) and for variation of the inner inductance as well as for the equivalent radius coeficient as a function of the relative permeability of the steel core.
The paper describes an analytical approach to the issue of skin effect on current or current dens... more The paper describes an analytical approach to the issue of skin effect on current or current density distribution over the cross-section of the tube type conductors. The same cross-section can analogical be taken for any multi-layer conductor of different construction designs. Due to the skin effect, the current flows towards the conductor surface, the result being an uneven current distribution over the conductor cross-section. A mathematical algorithm is given enebling determination of the current density distribution over the tube type cross-section. It is computed with the Maxwell's equation from the theory of electromagnetic fields and by using Bessel's functions of the first order. With thus implemented model the authors developed an algorithm for the current determination with consideration of the skin effect in the multi-layer ACSR 490/65 conductor and optic cable of the type OPGW. The result show the current density distribution in individual layers of ACSR 490/65 conductors with adiabatic heating at 1000 Aeff in the stady state. The same applies to the OPGW cable at the short-circuit current of 15.4 kAeff at the duration of 1s.
Pracenje grmljavine u realnom vremenu može biti ucinkovito sredstvo u voĎenju prostorno distribui... more Pracenje grmljavine u realnom vremenu može biti ucinkovito sredstvo u voĎenju prostorno distribuiranih sustava izloženih atmosferskim uvjetima. Danas takvi sustavi predstavljaju snažno oruĎe u projektiranju, zastiti i voĎenju elektroenergetskih mreža, a njihova je primjena i u drugim sustavima i mrežama kao sto su TK mreže, RTV odasiljaci, naftovodi, plinovodi, sustavi osiguranja, meteoroloski servisi, agencije za zastitu od požara i dr. Podaci pristigli iz raznih izvora obraĎuju se i pohranjuju u Oracle 11g instanci baze podataka. GIS podaci promatranih objekata na tlu prostorno se koreliraju s podacima o udarima munja u realnom vremenu koristenjem Oracle Spatial funkcionalnosti te se prezentiraju pomocu Autodesk MapGuide webGIS rjesenja.
The paper presents the methodology for calculation and measurement of induced voltage caused by r... more The paper presents the methodology for calculation and measurement of induced voltage caused by railway system operation on the sensitive metallic structures. The arrangement and characteristics of railway system 25 kV, 50 Hz are provided. The procedures of short-circuit current calculation and supply current measurement in the railway system are described. The basic theoretic background of inductive interference is explained. The reduction factors of the communication cable, railway system and environment are mentioned and clarified. On a case study, the results of the induced voltage calculation and measurement is compared. It is proved that induced voltage directly depends of supply current or shortcircuit value.
The study of the overvoltages generated by faults in the transmission distribution electrical net... more The study of the overvoltages generated by faults in the transmission distribution electrical network comprised over 500 live tests of a single phase-to-earth fault in a 10 kV network. The influence of the neutral point grounding resistance on overvoltages in the network is researched. Different values of the resistor were used. Moreover the networks with an insulated neutral point were tested. A computer model of the cable network and the supply station was additionally developed. Overvoltages are reduced to relatively low values, mostly below the value of a double phase peak voltage, if the neutral point of the network 10(20) kV is grounded through the resistor. This is under a condition that the nominal resistor current is three times greater than the earth fault capacity current.
International Journal of Electrical Power & Energy Systems, Mar 1, 2020
The paper demonstrates the importance of taking the frequency-dependence of the tower grounding i... more The paper demonstrates the importance of taking the frequency-dependence of the tower grounding impedance into account when studying the lightning performance of an overhead line located in an area with high soil resistivity. Towers' impulse grounding impedance measurements and their rational approximations are used to construct a wideband model of the towers' grounding electrodes in an EMTP-type software program. In order to examine the impact of tower grounding impedances, simulations of lightning strokes to the overhead line tower were performed using an EMTP-type tool in the following three different cases: constant grounding impedance of the tower hit by a lightning stroke, frequency-dependent tower grounding impedance and frequency-dependent tower grounding impedance for the tower equipped with a Line Surge Arrester (LSA) installed at the lowest phase. The simulations have shown the influence of the frequency-dependence of the tower grounding impedance on the level of the build-up voltage across the tower's insulator string and consequently on the flashover occurrence in the observed configuration with a high soil resistivity.
The method and models are developed in the study of power supply for 2x25 kV Hungarian railway tr... more The method and models are developed in the study of power supply for 2x25 kV Hungarian railway track, which is supplied from the Croatian conventional 25 kV system. Mathematical formulas and procedures are given in order to describe behaviour and performance of the electrical railway system, from utility feeding point to train contact point. Computer program based on the described method is used in the analysis. Typical results are shown.
Knjiga Napajanje elektricne vuce obrađuje osnovnu problematiku sustava napajanja elektrificiranih... more Knjiga Napajanje elektricne vuce obrađuje osnovnu problematiku sustava napajanja elektrificiranih pruga. Namijenjena je studentima na diplomskom i poslijediplomskom sveucilisnom studiju koji izucavaju građu vezanu uz elektricne željeznice. Može biti korisna i mnogim strucnjacima koji se na bilo koji nacin bave tim problemima u praksi.
Studija je provjerila mogucnosti prikljucka 6 novih EVP-a za napajanje nove željeznicke pruge na ... more Studija je provjerila mogucnosti prikljucka 6 novih EVP-a za napajanje nove željeznicke pruge na prijenosnu elektroenergetsku mrežu s razlicitih aspekata. U predmetnoj studiji pokusalo se sto realnije sagledati stvarne mogucnosti razvoja prijenosne mreže, te definirati minimalne zahtjeve za izgradnjom novih prijenosnih objekata neophodnih za sigurno napajanje novih EVP-a, vodeci pri tom racuna da se postojecim potrosacima ne narusi pouzdano napajanje kvalitetnom elektricnom energijom. Buduci da je rijec o prikljucku nesimetricnih potrosaca na prijenosnu mrežu, svi proracuni tokova snaga i analize sigurnosti N-1 provedeni su programskim paketom za trofazni proracun tokova snaga. Proracuni su provedeni uz uvažavanje stvarnog nacina prikljucka postojecih EVP-a na prijenosnu mrežu i njihovog planiranog porasta opterecenja u promatranom periodu do nazivne 2016., odnosno 2020. godine. Na taj je nacin omoguceno cjelovito sagledavanje problematike naponskih i strujnih nesimetrija, sto je u skladu s Mrežnim pravilima HOPS-a. Osim navedenih proracuna tokova snaga i analiza sigurnosti N-1, provedeni su i proracuni maksimalnih i minimalnih struja trofaznog, jednofaznog i dvofaznog kratkog spoja. Proracuni su provedeni prema međunarodnom standardu IEC 60909. Rezultati proracuna maksimalnih struja kratkog spoja koristeni su za provjeru dimenzioniranja postojece i nove rasklopne opreme u prijenosnoj mreži, dok su rezultati proracuna minimalnih struja kratkog spoja koristeni za procjenu varijacija napona i razine emisije flikera, te visih harmonika uslijed prikljucka novih EVP-a.
The paper discusses the issue of skin effect impact on the current distribution or on the current... more The paper discusses the issue of skin effect impact on the current distribution or on the current density over the conductor cross-section The consequence of the skin effect, which drives the current towards the conductor surface, is an uneven current distribution over the conductor cross-section. A mathematical algorithm is presented enebling the determination of the current density distribution over the tube conductor cross-section. The algorithm is computed with the Maxwell's equation from the theory of electromagnetic fields and by using Bessel's functions of the first and second order. With thus implemented model the authors developed an algorithm for the current density determination with consideration of the skin effect impact on the multi-layer bare conductor for overhead power transmission lines of the ACSR 490/65 type. Results are given for the current density distribution over individual layers of the observed conductor (the steel core and three conductive aluminum layers) and for variation of the inner inductance as well as for the equivalent radius coeficient as a function of the relative permeability of the steel core.
The paper describes an analytical approach to the issue of skin effect on current or current dens... more The paper describes an analytical approach to the issue of skin effect on current or current density distribution over the cross-section of the tube type conductors. The same cross-section can analogical be taken for any multi-layer conductor of different construction designs. Due to the skin effect, the current flows towards the conductor surface, the result being an uneven current distribution over the conductor cross-section. A mathematical algorithm is given enebling determination of the current density distribution over the tube type cross-section. It is computed with the Maxwell's equation from the theory of electromagnetic fields and by using Bessel's functions of the first order. With thus implemented model the authors developed an algorithm for the current determination with consideration of the skin effect in the multi-layer ACSR 490/65 conductor and optic cable of the type OPGW. The result show the current density distribution in individual layers of ACSR 490/65 conductors with adiabatic heating at 1000 Aeff in the stady state. The same applies to the OPGW cable at the short-circuit current of 15.4 kAeff at the duration of 1s.
Pracenje grmljavine u realnom vremenu može biti ucinkovito sredstvo u voĎenju prostorno distribui... more Pracenje grmljavine u realnom vremenu može biti ucinkovito sredstvo u voĎenju prostorno distribuiranih sustava izloženih atmosferskim uvjetima. Danas takvi sustavi predstavljaju snažno oruĎe u projektiranju, zastiti i voĎenju elektroenergetskih mreža, a njihova je primjena i u drugim sustavima i mrežama kao sto su TK mreže, RTV odasiljaci, naftovodi, plinovodi, sustavi osiguranja, meteoroloski servisi, agencije za zastitu od požara i dr. Podaci pristigli iz raznih izvora obraĎuju se i pohranjuju u Oracle 11g instanci baze podataka. GIS podaci promatranih objekata na tlu prostorno se koreliraju s podacima o udarima munja u realnom vremenu koristenjem Oracle Spatial funkcionalnosti te se prezentiraju pomocu Autodesk MapGuide webGIS rjesenja.
The paper presents the methodology for calculation and measurement of induced voltage caused by r... more The paper presents the methodology for calculation and measurement of induced voltage caused by railway system operation on the sensitive metallic structures. The arrangement and characteristics of railway system 25 kV, 50 Hz are provided. The procedures of short-circuit current calculation and supply current measurement in the railway system are described. The basic theoretic background of inductive interference is explained. The reduction factors of the communication cable, railway system and environment are mentioned and clarified. On a case study, the results of the induced voltage calculation and measurement is compared. It is proved that induced voltage directly depends of supply current or shortcircuit value.
The study of the overvoltages generated by faults in the transmission distribution electrical net... more The study of the overvoltages generated by faults in the transmission distribution electrical network comprised over 500 live tests of a single phase-to-earth fault in a 10 kV network. The influence of the neutral point grounding resistance on overvoltages in the network is researched. Different values of the resistor were used. Moreover the networks with an insulated neutral point were tested. A computer model of the cable network and the supply station was additionally developed. Overvoltages are reduced to relatively low values, mostly below the value of a double phase peak voltage, if the neutral point of the network 10(20) kV is grounded through the resistor. This is under a condition that the nominal resistor current is three times greater than the earth fault capacity current.
International Journal of Electrical Power & Energy Systems, Mar 1, 2020
The paper demonstrates the importance of taking the frequency-dependence of the tower grounding i... more The paper demonstrates the importance of taking the frequency-dependence of the tower grounding impedance into account when studying the lightning performance of an overhead line located in an area with high soil resistivity. Towers' impulse grounding impedance measurements and their rational approximations are used to construct a wideband model of the towers' grounding electrodes in an EMTP-type software program. In order to examine the impact of tower grounding impedances, simulations of lightning strokes to the overhead line tower were performed using an EMTP-type tool in the following three different cases: constant grounding impedance of the tower hit by a lightning stroke, frequency-dependent tower grounding impedance and frequency-dependent tower grounding impedance for the tower equipped with a Line Surge Arrester (LSA) installed at the lowest phase. The simulations have shown the influence of the frequency-dependence of the tower grounding impedance on the level of the build-up voltage across the tower's insulator string and consequently on the flashover occurrence in the observed configuration with a high soil resistivity.
The method and models are developed in the study of power supply for 2x25 kV Hungarian railway tr... more The method and models are developed in the study of power supply for 2x25 kV Hungarian railway track, which is supplied from the Croatian conventional 25 kV system. Mathematical formulas and procedures are given in order to describe behaviour and performance of the electrical railway system, from utility feeding point to train contact point. Computer program based on the described method is used in the analysis. Typical results are shown.
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Papers by Ivo Uglešić