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The paper presents types of ferroresonance as well as a part of the electrical power network in which the ferroresonance could occur. The experimental investigation of the ferroresonant parts of the electrical power network is not practically possible. Therefore, an experimental ferroresonant circuit is realized in the laboratory as a physical model of a ferroresonant part of the electrical power network, based on the 230-kV Converter Station Dorsey (Manitoba, Canada). Per-unit parameter values of the experimental ferroresonant circuit and 230-kV Converter Station Dorsey are compared as well as the results obtained from the measurements.

The drive by the government of Tanzania to electrify every village has resulted into expansion of the electrical secondary distribution networks (ESDNs). Therefore, maintenance management is of the highest priority for the smooth operation of the ESDNs to reduce unscheduled downtime and unexpected mechanical failures. Studies show that condition-based predictive maintenance (CBPdM) method allows the utility company to monitor, analyze and process the information obtained from ESDNs transformers. Thus, this study adopts the CBPdM method to develop a maintenance scheduling algorithm that can predict the transformer state, forecast maintenance time based on transformer load profile and schedule its maintenance using a knowledge-based system (KBS). Applying the challenge driven education approach, the requirements for developing an algorithm were established through an extensive literature survey and engagement of the key stakeholders from the Tanzania utility company. Our study uses the Dissolved Gas Analysis tool to collect the transformer parameters used in algorithm design. The parameter analysis was performed using Statistical Package for Social Sciences software. Results show that the designed KBS algorithm minimizes human-related maintenance errors and lowers labour costs as the system makes all the maintenance decisions. Specifically, the proposed maintenance scheduling algorithm reduces downtime maintenance costs by 1.45 times relative to the classical inspection-based maintenance model while significantly saving the maintenance costs. Keywords: Electrical power network, Forecasted load consumption, Knowledge-Based System, Maintenance Scheduling, Predictive Maintenance, Secondary Distribution

Приводится краткий обзор тенденций развития расчётов, анализа и нормирования потерь электроэнергии за последние 40 лет в электрических сетях бывшего СССР и постсоветских России и Казахстана. Показано, что наиболее объективным способом нормирования потерь, анализа их структуры, обоснования и выбора мероприятий по снижению потерь являются расчёты технических потерь и их структуры по уровням напряжения, основанные на классических законах электротехники. Представлены методика нормирования и прогнозирования потерь и примеры расчётов структуры балансов электроэнергии в электрических сетях Казахстана. Обоснована необходимость технико-экономического, а не административного управления потерями электроэнергии., The article briefly reviews trends in the development of electricity losses calculations, analysis and rationing over the past 40 years in the electrical networks of the former USSR, post-Soviet Russia and Kazakhstan. It demonstrates that technical losses calculation and losses structure by voltage levels based on electrical engineering classical laws is the most objective method of rationing losses, analyzing their structure, justification and selection of losses mitigation measures. It also presents rationing and forecasting losses methods and representative calculations of the electricity balances structure in Kazakhstan electrical networks. Then it substantiates the necessity of techno-economical electricity losses management instead of the administration., №11(1060) (2019)

Zadnje 10 letno obdobje je obdobje obnov in rekonstrukcij elektroenergetskega omrežja. Razdelilna transformatorska postaja Podlog je eden izmed pomembnejših elektroenergetskih objektov v Sloveniji. Z vgradnjo novih proizvodnih zmogljivosti v Termoelektrarni Šoštanj je potreba po zanesljivem obratovanju še večja. Z rekonstrukcijo stikališča in vgradnjo nove transformacije 400/110 kV se bo zanesljivost napajanja na območju RTP Podlog močno povečala. Zaradi nenehnega večanja porabe električne energije so rekonstrukcije in obnove nujno potrebne. Po končani vgradnji transformacije 400/110 kV bo RTP Podlog pripravljena na nove izzive. v Sloveniji bo RTP Podlog eden izmed najsodobnejših objektov. V celoti z elektroenergetskim omrežjem bo sposobna zagotavljati zanesljivo oskrbo z električno energijo. The last 10 year period is the period of renewals and extensions of the electricity grid. The Podlog substation is one of the most inportant electricity facilities in Slovenia. with the installation of new production capacity in the Šoštanj Thermo power plant is the need for fail-safe operation is even greater. With the reconstruction the Podlog substation and installation a new transformation 400/110 kV will be the reliability of power supply in the range of Podlog substation greatly increased. Due to the continuous increase in the consumption of electricity the extensions and renewals are necessary. After finishing the installation of transformation 400/110 kV, Podlog substation will be ready for new challenges. In Slovenia will be one of the most modern facilities. Fully with the electricity network will be able to provide a reliable supply of electricity.

Icing on power lines may lead to compromise safety and reliability of electric supply network. Prolong icing can lead to power breakdown and collapse of towers. Since power transmission lines are mostly overhead and could face the direct impact of icing, and it is one of the main challenges faced by power distribution companies in cold regions. When the ice accretion crosses the safety limit then deicing action can be carried out. We can find number of deicing methods that are used in different parts of the world. However, all of these deicing techniques have their own advantages and disadvantages on implementation. It is one of the most difficult as well as dangerous process to perform deicing on power lines. If a fault is detected and that has been occurred due to icing or during routine maintenance, extra care must be taken in order to ensure safety of the personals when performing de-icing of lines. However, as technology evolved, new ways and techniques are adopted with the help of sensors that give quick feedback to control room in the national grid via wireless communication network for real time action. In the thesis we have discussed atmospheric icing impacts on power lines in the cold regions across the world. A literature review has been done for anti-icing and deicing methods that are currently adopted in the power distribution network. Methods that are used against ice buildups have also been analyzed. This work also shows the impacts of icing and deicing techniques presently adopted, and also throws light on their pros and cons during maintenance operations. It provides an overview of the evolving technology trends that are practiced to ensure the availability of existing power transmission system in cold climate regions.

Zadnja obnova stikališča 110kV v RTP Selce, je bila v letih 1979 do 1987, Naprave so tehnološko že precej zastarele, celotno stikališče pa je bilo zasnovano v petdesetih letih prejšnjega stoletja glede na takratne potrebe. Dandanes pa obratovalno težko izpolnjuje zahteve v elektroenergetskem sistemu Slovenije. V diplomskem delu je predstavljeno sedanje stanje stikališča 110kV RTP Selce, opisane so naprave ki trenutno obratujejo (zbiralke, odklopniki, ločilniki). Opisani so vzroki za prenovo stikališča in cilji rekonstrukcije, opisano je potrebno dimenzioniranje naprav in izbira samih naprav GIS postroja ter predstavitev le-teh. The last reconstruction of 110 kV substation Selce was carried out in the period from 1979 to 1987. Entire substation was designed in the fifties of last century according to the needs of that time and is today consequently faced with difficulties in meeting operational requirements in the electricity system of Slovenia. The thesis presents the current condition of 110 kV substation Selce, describes currently operating devices (busbars, circuit breakers, disconnectors). It also describes and explains the reasons for and the goals of its planned reconstruction and contains a description of dimensioning of the neccessary devices and selection of GIS unit devices and their introduction.

Razdelilna transformatorska postaja Podlog sodi med večje in pomembnejše prenosne objekte v Sloveniji, saj ne skrbi le za nemoteno napajanje celjskega in zasavskega bazena, temveč je tudi ključno vozlišče za daljnovodne povezave 400 in 220 kV. Zaradi pomena in vloge RTP Podlog v Slovenskem elektroenergetskem sistemu je ELES v zadnjih letih v prenovo tega stikališča tudi drugače vlagal precejšnja sredstva. Vgrajene so bile najsodobnejše naprave, kar omogoča večjo zanesljivost naprav za nemoteno delovanje trga z električno energijo. Prav tako je bila zamenjana sekundarna oprema, pri čemer je bil uporabljen tudi nov koncept opremljenosti zveznih polj, ki omogoča, da lahko prenovljeno zvezno in merilno polje prevzame funkcije rezervnega polja ob popravilu morebitnih okvar, s čimer so bili že doseženi precejšnji prihranki. The Podlog Substation is one of the largest and most important transmission facilities in Slovenia. It is not only rensposible for the undisturbed supply of electric power to the Celje and Zasavje region, but is also a key node for transmission connections 400 kV. Because of the role and significance of the Podlog Substation in the Slovene electric power system, ELES invested substantial funds in past years in the renewal of this switch yard. The most up-to-date devices were instaled, ensuring greater reliability of facilities for the undisturbed operation of the electric power market. The secondary equipment was entirely replaced and a new concept of equipping parallel bays was introduced. This concept allows the coupling and measuring bay to assume the function of a spare bay in the event of eventual breakdowns, and has already brought considerable savings.

Zadnja obnova primarne in sekundarne opreme 110 kV stikališča v RTP Laško je bila med leti 1979 in 1981. Zaradi tehnološko zastarelih naprav je upravljanje in nadziranje le-teh že vprašljivo. Prav tako RTP Laško ni mogoče vključiti v nadzorne centre, ki omogočajo hitrejše vpoglede in zajem podatkov za analize. V diplomskemu delu je predstavljeno sedanje stanje 110 kV stikališča RTP Laško z opisom primarne opreme (odklopnik in ločilnik) in sekundarne opreme (zaščita, vodenje in sistem lastne rabe). Podani so vzroki za prenovo ter zahteve in cilji rekonstrukcije. Izvedeno je dimenzioniranje stikalnih aparatov in naprav novega stikališča. Za izbiro visokonapetostne opreme (odklopnik in ločilnik) 110 kV stikališča so podani različni tipi posamezne VN opreme z ustreznimi podatki in z opisom delovanja. Predstavljena je še sekundarna oprema novega 110 kV stikališča za vodenje, zaščito in sistem lastne rabe. The last renovation of the primary and secondary equipment in 110 kV switching substation in transformer substation Laško was held between 1979 and 1981. Because of the technologically obsolete equipment the running and controlling of switching substation already became uncertain. Transformer substation Laško cannot also be included in the control centres enabling faster data analysis. The thesis presents the present state of the 110 kV switching substation in transformer substation Laško with the description of the primary equipment (circuit breaker and disconnector) and secondary equipment (protection, control and the self-use system). There are given some reasons for the renovation and reconstruction requirements and objectives. Moreover, the dimensioning of switchgears and a new equipment of the switching substation is implemented. Furthermore, different types of individual high-voltage equipment with the relevant information and a description of the operation are given for the selection of high-voltage equipment (circuit breaker and disconnector) of 110 kV switching substation. And lastly, there is also presented the secondary equipment of the new 110 kV switching substation for the control, protection and self-use system.

V doktorski disertaciji je predstavljen pristop k reševanju različnih optimizacijskih problemov v domeni elektroenergetskega omrežja. Pri tem so predstavljeni rezultati in podrobnosti aplikacij optimizacijskih algoritmov pri reševanju optimizacijskih problemov elementov kot so transformator, podporni kompozitni izolator, plinski odvodnik ter skoznjik, kot tudi primer določanja optimalne konfiguracije srednjenapetostnega omrežja. Kot primarna optimizacijska tehnika je bil uporabljen evolucijski algoritem imenovan diferenčna evolucija. Njegova slabost, ki je sorodna vsem evolucijskim algoritmom, je veliko število cenitev kriterijske funkcije, potrebnih za doseganje konvergence optimizacijskega postopka. Izboljšanje omenjene slabosti je bilo v okviru disertacije realizirano z razširitvijo izvirnega algoritma oz. z njegovo dopolnitvijo s Kriging interpolacijsko metodo. Preskusi na različnih standardnih testnih funkcijah kot tudi na realnem inženirskem problemu so pokazali, da potrebuje novi algoritem v primerjavi z izvirnim povprečno pol manj cenitev dejanske kriterijske funkcije. In this thesis an approach for solving various optimization problems in area of electrical power network elements is presented. Results and details of optimization algorithm applications for solving various elements, such as transformer, post composite insulator, gas discharge arrester, bushing and network configuration problem are also given. Well known evolutionary algorithm, Differential evolution, has been selected as a fundamental optimization technique. Its downside, which is common to all Evolutionary algorithms, is the required large number of iterations, respectively the number of function evaluations in order to achieve the convergence. To improve this property of Differential evolution algorithm, one has been extended to use Kriging interpolation method. Newly developed Kriging-assisted differential evolution algorithm enables the reduction of required function calls. Experiments, which had been conducted on several standard test functions, and also on a real engineering problem, have shown that new algorithm, compared to original Differential evolution algorithm, generally reduces a number of actual function calls by half.

V magistrskem delu je prikazana izvedba in praktični primer sodobnega visokonapetostnega 400 kV zračno in s plinom SF6 izoliranega stikališča. Predstavljene so naprave novega bloka 6 Termoelektrarne Šoštanj. V nadaljevanju je prikazana in argumentirana idejna zasnova stikališča za blok 6 s primerjavo med zračno izolirano in plinsko izolirano izvedbo. Glede na karakteristike energetske opreme bloka 6 in analize sosednjih stikališč so bili opravljeni ustrezni izračuni kratkostičnih razmer. Na osnovi teh izračunov je bila izbrana ustrezna oprema zračno in s plinom SF6 izoliranega stikališča. Za takšni izvedbi stikališč so bili izvedeni izračuni vplivov na okolje. Analizirana je bila tudi vključitev omenjenih stikališč v elektroenergetski sistem na osnovi analize z zanesljivostnim kriterijem "n-1" in izračunom obremenljivosti za več variant vključitve bloka 6 v elektroenergetski sistem. Implementation and a practical example of high-voltage 400 kV air and gas SF6 insulated substation are shown in this master’s thesis. Different devices of the new block 6 of the thermal power plant Šoštanj are presented. The switching substation for block 6 in comparison with air insulated and gas insulated performance is argumentatively presented in the continuation. According to the block 6 energy equipment characteristics and adjoining switching substation analysis suitable calculations are made for short-circuit circumstances. On the basis of these calculations suitable equipment for air and gas SF6 insulated substation is chosen. For this kind of performances environmental effect calculations are made as well. Inclusion of the above mentioned switching substation in electrical power system is analysed in the thesis. Analysis of different varieties for block 6 inclusions in the electrical power system is made with reliable criteria “n-1” and the calculation of load in a system.

In overall expansion of power distribution and sub-transmission (10 kV - 110 kV) networks, conditioned with growing consumption of electrical power, there is an increasing of possibility for crossing underground power cables with home electrical installation cables, telecommunication equipment cables and other equipment. Furthermore, surge arresters on middle-voltage levels usually are not applied along overhead lines. Above mentioned can affect on equipment or even human life safety. It is known that interference of the different electrical installations and equipment is the main theme of researching in Electromagnetic Compatibility (EMC). In this article, a possibility of using the Finite Element Method (FEM) for EMC calculations in practice, is explored and presented. For that purpose, a real problem from distribution power network will be used for an illustrative example. It is worth of mentioning that FEM technique is quite a new tool in power networks calculations area.

V diplomski nalogi je predstavljen potek dimenzioniranja ter izbira opreme in aparatov nove transformatorske postaje TP Formalin 2 in vključitev le te v elektroenergetsko omrežje Nafte Lendava. Opisano je tudi elektroenergetsko omrežje Nafte Lendava in lastna industrijska elektrarna.V nalogi so izvedeni izračuni kratkih stikov na srednjenapetostni in nizkonapetostni strani, ki so bili nato uporabljeni za nadaljnje dimenzioniranje aparatov in naprav. Izvedena je tudi kontrola zbiralk ter odvodnih stikal The thesis represents the dimensioning course and the selection of the equipment and devices of the new transformer station TP Formalin 2 and it's inclusion into the electrical power network of Nafta Lendava. It also gives a short insight into the electrical power network of Nafta Lendava and it's own industrial power plant. In the thesis, the short circuit calculations on the middle- and low-voltage side are performed which were then used for further dimensioning of the equipment and devices. In addition

Electrical Power Network in recent time requires an intelligent, virtual environment based decision process for the coordination of all its individual elements and the interrelated tasks. Its ultimate goal is to achieve maximum productivity and efficiency through the efficient and effective application of generation, transmission, distribution, pricing and regulatory systems. However, the complexity of electrical power network and the presence of conflicting multiple goals and objectives postulated by various groups emphasized the need of an intelligent group decision support system approach in this field. In this paper, an Integrated Multimedia based Intelligent Group Decision Support System (IM1GDSS) is presented, and its main components are analyzed and discussed. In particular attention is focused on the Data Base, Model Base, Central Black Board (CBB) and Multicriteria Futuristic Decision Process (MFDP) module. The model base interacts with Electrical Power Network Load Forecasting and Planning (EPNLFP) Module; Resource Optimization, Modeling and Simulation (ROMAS) Module; Electrical Power Network Control and Evaluation Process (EPNCAEP) Module, and MFDP Module through CBB for strategic planning, management control, operational planning and transaction processing. The richness of multimedia channels adds a totally new dimension in a group decision making for Electrical Power Network. The proposed IMIGDSS is a user friendly, highly interactive group decision making system, based on efficient intelligent and multimedia communication support for group discussions, retrieval of content and multi criteria decision analysis.