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Izolatorji so vedno predstavljali pomemben element, ki se uporablja na vseh nivojih elektroenergetskega sistema, tako pri proizvodnji, prenosu in distribuciji električne energije. Njihova glavna vloga je izolacija delov pod napetostjo od ozemljenih delov, ki se odraža v njihovi dielektrični zdržnosti za različne napetostne nivoje. Prav tako so lahko značilno mehansko obremenjeni, odvisno od njihovega namena. Zgodovinsko so stekleni izolatorji v uporabi že več kot stoletje. S časom so prišli na drugo raven za zanesljivo in reprezentativno obratovanje, in sicer zaradi boljše odpornosti proti staranju in vplivom iz okolja. Glavne izboljšave so se pri tehnologiji obdelave steklenega dielektričnega materiala odražale v kaljenju, prilagajanju oblike stekla za boljše delovanje v zahtevnem okolju, doseganje hidrofobnih lastnosti s polimernim premazom steklenega dela itn. Skozi desetletja so bili zahtevani prehodi na višje napetostne nivoje in posledično so stekleni izolatorji morali biti daljši, da bi lahko nadzemni vodi prenašali več električne energije, zato se je njihova teža povečala. Posledično je teža in dolžina izolatorjev močno vplivala na obremenitev stebrov. Alternativna uporaba polimernih izolatorjev prinaša reševanje, ne samo problema teže, temveč tudi drugih dielektričnih lastnosti, ki steklenim izolatorjem primanjkujejo. Kompozitni polimerni izolatorji, ki so v uporabi že približno 50 let, v začetku niso predstavljali prve izbire uporabnikov, predvsem zaradi pomanjkanja izkušenj povezanih z njihovim nepredvidljivim staranjem in možno degradacijo. Z razvojem boljših materialov in novih proizvodnih postopkov je privedlo do izkazovanja njihove sposobnosti za izpolnitev strogih zahtev obratovanja tudi na onesnaženih območjih. Druga prednost uporabe kompozitnih polimernih izolatorjev je bila v možnosti drugačne konstrukcije, znane pod angleškim izrazom »cross-arm«, ki je odprla možnosti prehoda na višji napetostni nivo na že obstoječih stebrih, hkrati pa tudi omogoča povečanje razdalj med deli pod napetostjo do zemlje kot tudi medfaznih razdalj v glavi stebra. Obe vrsti izolatorjev imata določene prednosti in specifične lastnosti, s katerimi ob pravilnem dimenzioniranju in kvalitetni izdelavi lahko izpolnijo zahteve za dotično območje uporabe. Čeprav v tej analizi mehanski vidik ni bil upoštevan, je vpliv mehanske obremenitve izolatorjev zelo pomemben predvsem iz vidika dolgotrajne uporabe v danem okolju in ga morajo projektanti upoštevati skladno s standardom SIST EN 5041-1:2013. Ne glede na vrsto in material, so izolatorji med obratovanjem izpostavljeni električnim in mehanskim obremenitvam, ki so posledica neenakomerne porazdelitve potenciala med deli pod napetostjo in ozemljeni deli. Prav tako je bil pri tem upoštevan vpliv korone, ki ga je potrebno predhodno preučiti. Električni potencial in izračun električnega polja temeljita na teoriji elektromagnetizma in Maxwellovih enačb. Za analizo porazdelitev električnega potenciala in električnega polja na izolatorju se izračuni opravijo ob upoštevanju zakonov elektrostatike. Ko gre za modeliranje kompleksnih geometrij in oblik, je potrebno uporabiti zanesljive in natančne postopke, saj izračuni in rezultati odražajo natančnost teh metod. Ena izmed uveljavljenih metod je metoda končnih elementov (MKE). Reševanje fizikalnih problemov po tej metodi opisujemo predvsem s parcialnimi diferencialnimi enačbami in so težavni za analitične izračune. Osnovno načelo metode končnih elementov je diskretizacija geometrije in oblike v majhne dele, imenovane končni elementi. Ko je domena razdeljena na majhne elemente, omogoča aproksimacijo željene količine, na primer električnega potenciala, s preprostimi funkcijami (linearno, kvadratično ali kubično). Se pravi, čim je bolj natančno diskretizirana geometrija in posledično aproksimacija parcialna diferencialna enačba, bolj natančni so doseženi rezultati. Metoda končnih elementov je močna zaradi svoje sposobnosti ukvarjanja z nepravilnimi oblikami in nehomogenimi materiali. Za kompozitne in steklene izolatorje so bili ustvarjeni 3D modeli s programskim orodjem COMSOL Multiphysics, ki temelji na metodi končnih elementov in se uporablja za analizo na področjih, kot so elektromagnetika, strukturna mehanika, akustika, dinamika tekočin, toplote in mase. Kot najpomembnejši del modeliranja se predprocesiranje opravi na tak način, da se zagotovi natančnost mreže elementov in rezultatov. Analiza porazdelitve električnega polja, ko govorimo o električni obremenitvi, se opravi pri različnih dimenzijah in položajih koronskih obročev za obe vrsti izolatorjev. Ko je bila dosežena željena porazdelitev električnega potenciala, se je prilagodilo dolžino obeh izolatorjev z namenom ohranitve izkriščne razdalje skladno s standardiziranimi zahtevami. Insulators have always represented important equipment used for electric energy production, transmission, and distribution of electrical power system. In general, their main role is to isolate equipment or parts of it that are grounded from the ones that are energized. Also, they may often be mechanically loaded, depending on their purpose. Historically, glass insulators have been in service for more than a century and their prior use was as telegraph insulators, though improvements were necessary for exploitation in electrical power system. Through many generations, glass insulators have been taken to another level for reliable and representative service, namely due to their good resistance against aging under environmental influence. Main upgrades were in glass as dielectric material – toughening, adjusting shape of the glass shell for better performance in demanding environment, achieving hydrophobic properties by polymer coating of glass insulators, etc. Through decades, transitions to higher voltage levels were demanded and glass insulators had to be longer to withstand applied voltage, therefore their weight had increased, and they had loaded towers significantly. Alternatively, the idea of polymer insulators would not only solve the problem regarding weight but would also propose other dielectric properties that glass insulators are in lack of. Composite polymer insulators, which have been in service for around 50 years, in the beginning were not users’ preferable choice, due to lack of experience of their unpredictable ageing degradation. Yet, improvement of materials and outcome of manufacturing process led to highlighting their ability to meet strict demands of service in polluted areas. Other benefit of introducing composite polymer insulators was in possibility of different construction known as cross arm, which opened opportunities such as transition to higher voltage level on already existing towers, while simultaneously increasing all clearance distances: phase to cross arm, phase to shield wire, and phase to ground. Both types of insulators have specific advantages and valuable properties that, if designed and manufactured properly, will fulfill requirements for a certain area. Although mechanical aspect is not considered in this thesis, influence of mechanical loading of insulators is time dependent, and taking it into account according to standard SIST EN 5041-1:2013 and should not be negotiable for any designer and manufacturer. Regardless of type and material, insulators are exposed to electrical and mechanical stress during exploitation. Focusing on electrical stress, which is caused by unequal potential distribution from energized to grounded part of insulator and corona discharge, it must be studied in advance. Electric potential and electric field calculation is based on theory of electromagnetism and Maxwell’s field equations. For analysis of electric potential and electric field distributions on insulators, calculation of both is done in the manner of electrostatics. When it comes to modeling complex geometry and shapes, reliable and precise methods must be used, since calculations and results rely on method’s preciseness. One of popular methods with these benefits is Finite Element Method. Since laws of physics are mainly described with partial differential equations, making them demanding for analytical calculation, this method proposes discretization of geometry and shapes into small subdomains, called finite elements. Once the domain is divided into small elements, it allows to approximate desired quantity, for example electric potential, by simple functions (linear, quadratic, or cubic function). This means that the more precise discretization of geometry and, consequently, approximation of partial differential equation are, the more precise results of this method are achieved. Finite element method is powerful due to its ability to deal with arbitrary shapes and inhomogeneous media. For both composite and glass types of insulator 3D models have been created in COMSOL Multiphysics software, based on FEM, and used for analysis in areas such as electromagnetics, structural mechanics, acoustics, fluid flow, heat, and mass transport. As the most important part of modelling, preprocessing is done in such manner to provide mesh preciseness and accuracy of results. Analysis of electric field distribution, when talking about electrical stress, is done with varying corona rings dimensions and position for both insulators. After achieving desirable distribution, length of both insulators has been changed to keep the arcing distance according to standardized requirements.

V diplomskem delu je predstavljen razvoj, zgradba ter obratovanje kompozitnih izolatorjev. Podrobneje je predstavljena uporaba 110 kV kompozitnih izolatorjev. Za poznavanje celotne problematike obratovanja kompozitnih izolatorjev, je potrebno podrobneje preučiti standarde, ki opisujejo kompozitne izolatorje, predstaviti dosedanjo problematiko v slovenskem elektroenergetskem sistemu, preučiti analizo stanja izolatorjev, ki so bili več let v obratovanju, ter preučiti izkušnje z obratovanjem kompozitnih izolatorjev v elektroenergetskih sistemih tujih držav. The thesis presents the development, composition and operating of composite insulators. The use of 110 kV composite insulators is presented in detail. In order to understand the whole problem of composite insulator operations it is necessary to study standards, describing composite insulators, present the existing problems in the Slovenian power system, study the analysis of the state of insulators, that were in use for many years, and study the experiences with the use of composite insulators in power systems of foreign countries.

V diplomskem delu je predstavljen razvoj podpornega kompozitnega izolatorja s kapacitivnim delilnikom. Opisane so električne in mehanske lastnosti kompozitnih izolatorjev v primerjavi s klasičnimi izolatorji. Predstavljena je zamisel o vgradnji elektrode v notranjost izolatorja, s pomočjo katere bi ustvarili kapacitivni delilnik. S pomočjo simulacije, ki temelji na metodi končnih elementov, je v programskem okolju OPERA Vector Fields predstavljena analiza različnih elektrod in njihov vpliv na kapacitivnost spodnjega priključka izolatorja. Opisan je standard IEC 61243-5, v katerem so predstavljene zahteve, ki jih mora izpolnjevati izolator s kapacitivnim delilnikom. Izdelana je projektna struktura za razvoj podpornega kompozitnega izolatorja, ki med drugim vključuje vhodne strategije, taktike, namenske in objektne cilje, analizo rizikov in časovni plan. Poleg tega so zbrani tudi stroški projekta do začetka serijske proizvodnje. Na koncu diplomskega dela je predstavljeno, kako naj bi potekala nadaljnja eksploatacija projekta, tako da bi bili doseženi zadani cilji projekta. In this diploma thesis the development of a support composite insulator with capacitive divider is presented. Electrical and mechanical properties of the composite insulator in comparison with classical insulators are described. Te idea of electrode installation into the interior of the insulator is introduced, with the help of which a capacitive divider can be created. With the help of a simulation based on the finite element method in the software OPERA Vector Fields the analysis of various electrodes and their influence on the capacitance of the lower insulator connector is presented. IEC standard 61243-5 is described, where the requirements for an insulator with a capacitive divider are introduced. A project structure for the development of a support composite insulator is prepared, which among other things includes input strategies, tactics, purposive and objective goals, risk analysis and time plan. Project costs until the beginning of the serial production are also assembled. At the end of the diploma thesis a further project exploitation for the fulfilment of the set project goals is proposed.