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U ovom radu opisani su modeli svih elemenata elektroenergetske mreže pri čemu je ponajviše opisan model energetskih transformatora te u zasebnom poglavlju i model četveronamotnog transformatora. Zatim je matematički opisana Newton-Raphson metoda proračuna tokova snaga te su navedeni koraci metode proračuna za elektroenergetsku mrežu. U posljednjem poglavlju dodan je jedan četveronamotni transformator koji spaja jednu realnu prijenosnu mrežu s distribucijskom mrežom na kojem su dodani jedna solarna elektrana, dva tereta te dva kabela i u ovakvoj mreži su izvršeni proračuni tokova snaga po Newton-Raphson metodi. Proračuni tokova snaga su izvršeni pri promjeni proizvodnje solarne elektrane te pri promjeni potrošnje tereta u distribucijskoj mreži na kojem je četveronamotni transformator priključen. Za svaku promjenu stanja mreže su uspoređeni rezultati u odnosu na prethodna stanja mreže te su opisani tokovi snaga unutar četveronamotnog transformatora. In this thesis the model of all elements of power grid were described, mostly the model on power transformers and in separate chapter the model of four-winding transformer. Then, the Newton-Raphson method of power flow calculation were mathematically described and the steps of this calculation method for the power grid are given. In the final chapter, a four-winding transformer was added that connects one real transmission grid with a distribution grid to which one solar power plant, two loads and two cables were added, and in that grid the Newton-Raphson power flow calculations were performed. Power flow calculations were performed when changing the production of the solar power plant and when changing the load consumption in the distribution network to which the four-winding transformer is connected. For each change in the state of the grid, the results are compared in relation to the previous states of the grid, and power flows within the four-winding transformer are described.

Tema ovog rada je upoznavanje problematike prijenosa električne energije na dugom prijenosnom vodu. Uz opisane karakteristične veličine voda te koristeći model diferencijalnog dijela prijenosnog voda duž duljine izvedena su sva tri oblika prijenosnih jednadžbi. Zatim je prikazan izgled π-modela i T-modela prijenosnog voda pomoću kojih su izvedene naponske i strujne prilike na početku voda. Također su izvedene karakteristične veličine voda koristeći približne i točne modele voda. Izveden je drugi oblik prijenosne jednadžbe za idealni vod te su za pojedina karakteristična pogonska stanja (prazni hod, kratki spoj, opterećenje prirodnom snagom) opisane strujne i naponske prilike na tom istom vodu. Na primjeru jednog realnog voda izračunate su strujne i naponske prilike korištenjem prijenosnih jednadžbi te π-modela i T-modela voda. The topic of this thesis is to get familiar with problems of transmission of electric energy on long transmission line. Along with described characteristic parameters of line and using differential model of line through the length, the transmission equations were derived. Next, by introducing π-model and T-model the voltage and current condition in the beginning of line were derived, alongside with characteristic parameters on medium line model and long line model. For the ideal transmission line the transmission equation were derived, and for the specific operating condition (open circuit, short circuit and natural power) the voltage and current condition on ideal transmission line were described. On one real transmission line, the voltage and current condition were calculated using transmission equations, π-model and T-model of line.

Rotenone in stripes is considered (among some beekeepers in Croatia) as an effective drug against Varroa destructor. It is usually sold in the form of carton paper stripes previously dipped in 5% liquid rotenone (in further text “originally packed rotenone”). In this work, a rotenone solution was prepared by dilution of 50g of the powdered product „Cube Powder Fish Toxicant, ( TIFA International LLC, USA, with a rotenone content 6.8%) in 100 ml BAS 220 (Solvent naphtha heavy aromatic, Banner Chemicals Ltd., UK). After extraction period of 30 min, solution was filtered and used for dipping carton paper stripes, equal to those used for „originally“ packed rotenone. Obtained concentration of rotenone solution was 3, 4%. At the same apiary 5 colonies were treated with 3, 4% rotenone, 5 colonies were treated by Bayer drug „Check Mite+“ and 5 colonies with „originally“ packed rotenone in stripes, i.e. 5% rotenone solution. In colonies treated by Check mite + the Varroa infestation fell from initial 5, 76% to 0, 61%, in those treated by „original“ rotenone it fell from initial 3, 87% to 0, 16%, and in colonies treated by prepared rotenone it fell from 2, 18% to 1, 82%. Not even one colony from the group treated by Check mite+, or the group treated by Rotenone in stripes, according to the method described by Büchler et.al., ADIZ 2005., did not have infestation level higher than 2%, which would require additional treatment, but 2 out of 5 colonies treated by obtained rotenone solution had Varroa infestation level higher than 2%.