Model trifaznega transformatorja za izračun vklopnega toka

FAŠALEK, JERNEJ (author), Miljavec, Damijan (mentor)

Energetski transformator je ključen element elektroenergetskega sistema, saj omogoča spremembo napetostnega nivoja. Z dvigom napetosti se znatno zmanjšajo izgube pri prenosu električne energije. Za zanesljivo obratovanje elektroenergetskega sistema morajo zanesljivo obratovati vsi njegovi elementi. Zato je ključnega pomena dobro poznavanje njihovih obratovalnih stanj. Stanje transformatorja, ki bi lahko imelo vpliv na zanesljivost elektroenergetskega omrežja, je zagotovo tudi stanje ob vklopu transformatorja v omrežje. Gre za pojav, ko skozi primarno navitje transformatorja steče razmeroma velik tok prehodne narave, ki se sčasoma zmanjša na vrednost magnetilnega toka. Ta prehodni pojav imenujemo vklopni tok transformatorja. Proizvajalcem transformatorjev in upravljavcem elektroenergetskih omrežij je v interesu, da dobro poznajo velikost in obliko toka ob vklopu za določeni transformator. Analitične formule za izračun vklopnega toka nam ne dajo zadovoljivih rezultatov, zato je potrebno izdelati model transformatorja za simulacijo vklopnega toka. Cilj te diplomske naloge je predstaviti fizikalno ozadje fenomena vklopnega toka in izdelati uporaben model trifaznega energetskega transformatorja za izračun poteka vklopnega toka. Model transformatorja izpeljemo tako, da iz zgradbe transformatorja določimo magnetno vezje. To magnetno vezje transformiramo v električno vezje, ki ga nato simuliramo v programskem okolju Matlab Simulink. Predstavljeni so rezultati simulacije vklopnega toka za 31,5 MVA tristebrni energetski transformator. Predstavljena je tudi analiza harmonskih komponent v vklopnem toku. Naredili pa smo tudi analizo vpliva določenih parametrov modela na velikost vklopnega toka.

• Language: Slovenian
• Keywords: transformator, vklopni tok, Simulink
• Work type: Undergraduate thesis
• Organization: FE - Faculty of Electrical Engineering
• Year: 2015
• PID: 20.500.12556/RUL-30625
• Publication date in RUL: 06.03.2015

Secondary language

• Language: English
• Title: Three Phase Transformer Modeling for Inrush Current Calculation

Abstract

A power transformer is one of the most important elements of the power network because it can change the voltage level. Increasing the voltage level means decreasing of losses in transmission lines. To have a reliable power network, all the network elements must work flawlessly. That is why it is crucial to investigate all possible operation states of network elements. A state of the transformer that could harm other network elements is its enenergization. During the energization a transformer pulls relatively high transient current from the system which eventually reduces to a magnetizing current. This transient phenomenon is called an inrush current. It is in the best interest of manufacturers and network operators to know the amplitude and shape of inrush current. There are some analytical formulas to calculate the inrush current but the results aren't totally accurate. That is why we need to build a transformer model to calculate the inrush current. This thesis presents the physical background of the inrush current phenomenon and a useful model of a three-phase power transformer for calculating the inrush current. The model is derived from a transformers magnetic circuit which is then transformed to electrical circuit using duality principal. The magnetic circuit is derived from transformer topology. The transformers electric circuit is simulated in Matlab Simulink environment. Results are presented for a three-legged 31,5 MVA power transformer. A harmonic analysis of the inrush current and a sensitivity analysis of models parameters are also presented.

• Keywords: transformer, inrush current, Simulink