Prenaponske pojave atmosferskog porijekla predstavljaju značajan izvor kvarova na nadzemnim vodovima. U ovom radu analizirani su atmosferski prenaponi na nadzemnim srednjenaponskim vodovima s izoliranim vodičima i nadzemnim srednjenaponskim kabelskim vodovima. Te dvije tehnologije predstavljaju alternativu klasičnim nadzemnim vodovima s golim vodičima. Iako se SN vodovi s izoliranim vodičima u svijetu koriste više desetljeća, u našim razdjelnim mrežama su još uvijek slabo rasprostranjeni. Nadzemni SN kabelski vodovi i u svjetskim okvirima predstavljaju novost i o iskustvima s njihovom uporabom ima vrlo malo podataka. U radu su načinjene analize prenapona izazvanih direktnim udarom munje kao i induciranih prenapona izazvanih udarom munje u blizini nadzemnog voda. Za izračune je korišten program ATP-EMTP. Iako inducirani prenaponi imaju znatno manje iznose od prenapona koji nastaju direktnim udarom munje, oni još uvijek mogu biti dovoljno visoki da izazovu kvarove na srednjenaponskim vodovima. Njihovo računanje je posebno složen problem. Za tu svrhu je u radu upotrijebljen model autora H. K. Høidalena. Taj model za izračun induciranih prenapona koristi tzv. Agrawalov model elektromagnetske sprege. Proračuni su provedeni za odabrane slučajeve vodova s različitim primijenjenim mjerama zaštite od prenapona. Dobiveni rezultati pokazuju utjecaj zaštitnih mjera na iznose atmosferskih prenapona te omogućuju usporedbu učinkovitosti različitih načina prenaponske zaštite. Ključne riječi srednjenaponski vodovi s izoliranim vodičima, nadzemni srednjenaponski kabelski vodovi, udar munje, atmosferski prenaponi, inducirani prenaponi, prenaponska zaštita

Overvoltages of atmospheric origin represent a significant cause of faults on overhead lines. In this thesis lightning overvoltages on medium-voltage overhead lines with covered conductors and on overhead medium-voltage cables are analysed. These two technologies represent an alternative to standard overhead lines with bare conductors. Although MV lines with covered conductors have been used throughout the world for several decades, their application in Croatian distribution networks is still limited. Overhead MV cables represent a new solution for overhead networks and there is still very little data on experiences with their application. Overvoltages caused by direct lightning strikes as well as induced overvoltages created by lightning strikes in the vicinity of overhead line are analysed in this thesis. ATP-EMTP program was used for overvoltage calculations. Although induced overvoltages have much smaller values than overvoltages caused by direct lightning strikes, they can still be high enough to create faults on MV lines. Calculation of induced overvoltages represents a very complex task. Model created by H. K. Høidalen was used in this work for that purpose. Model calculates induced overvoltages using the so-called Agrawal electromagnetic coupling model. Calculations were performed for selected cases of lines with applied different measures for protection against overvoltages. Obtained results show influence of protective measures on lightning overvoltages and allow comparison of efficiency of different means of overvoltage protection. Keywords medium-voltage overhead lines with covered conducotors, medium-voltage overhead cables, lightning strike, lightning overvoltages, induced overvoltages, overvoltage protection