This thesis deals with the issue of reconstruction 110/22kV distribution substation in economic point of view, where we will assess the benefits of a combination of their involvement using the discounted cost. It’s necessary to reconstruct distribution substation due to the increasing demand for electricity, upgrading equipment in the distribution systems, improve the reliability of electricity supply to customers, etc.. Distribution substation layout must meet conditions resulting from a law on energetics and operation of primary distribution networks.

The aim of this diploma work has been to work up a first study dealing with possibilities of enlargement of Slavětice substation with the new sources of Dukovany power-plant (EDU). In this work I am mentioning the linking of 400 kV Slavětice substation into the electricity system in Czech Republic and its coupling into the west-European UCTE system and I am also itemizing the basic data of neighbouring substations. Further I am describing the current state of 400 kV and 110 kV substations in Slavětice, their parameters and scheme. In this work I am mentioning basic information of nuclear reactor piles, coming into consideration for the prospective new pile construction in the premises of Dukovany substation and also reflections about possibilities of bringing out power of this new pile. In the following part of my diploma work there are stated proposals of different versions for enlarging the Slavětice 400 kV substation by a new outlet of new EDU source and the eventual overhead-line construction. I am mentioning the necessary substation arrangements for each proposed version, the scheme, eventually the proposal how to lay-out the new lines. Further there is stated here a proposal of outgoing feeder switchgear accessories for the new EDU pile and also the proposal for an entirely new substation, its description and scheme. An evaluation of all proposed versions of Slavětice substation enlargement for connecting new nuclear piles is stated in the outcome of the work.

The diploma thesis is dedicated to modern kiosk-type transformer substations PET, that are used when modernizing distribution network. Since such substations are placed on publicly accessible places it is really important that they are safe for service staff as well as for the public. Apart from the highest characteristic values stress is put upon the safety. Right construction, functionality and safety is verified using the type-tests as stated in ČSN EN 62271-202. In the last part of the thesis there are the methods and procedures of type-testing described.

The thesis titled Individual stand-by of incoming feeder of Energetika Třinec 6 kV substantion is theoreticaly and practically concived work that offers comprehensive information on automatic standby focused on the selected operation of Energetika Třinec. At present, the standby is in authention mode and thesis solves shutdown of transformer T5. The extract of automatic device indicates trouble-free operation and thesis focus on the power take-off for transformer T5. The theoretical part provides information about problems of own comsumption of power plants, automatic device of standby and protection of electrical equipment. Thesis also sloves the protection settings, which is supported by calculations of short-circuit currents. The practical part is formed from the suggestion of solution in accordance to current criteria and the evaluation of possible settings of protective automatic devices together with an assessment of implementation option of standby. The aim of the thesis is to perform analysis of standby and evaluate effects which causes shutdown of own comsumption part. The final part assesses current settings of protection based on calculated values. Existing protections are unsuitable and it is recomennded to deploy digital multi-stage protections as a replacement for present relay protections.

With the increasing demand for clean and renewable energy, new distribution network concepts, such as DC microgrids and distributed power generation networks, are being developed. One key component of such networks is the grid-interfacing DC-DC power converter that can transfer power bi-directionally while having a wide range of voltage step-up and step-down capabilities. Also, with the proliferated demand for electric vehicle chargers, battery energy storage systems, and solid-state transformers (SST), the bi-directional high-power DC-DC converter plays a more significant role in the renewable energy industry. To satisfy the requirements of the high-power bi-directional wide-range DC-DC converter, different topologies have been compared in this thesis, and the four-switch buck-boost (FSBB) converter topology has been selected as the candidate. This work investigates the operation principle of the FSBB converter, and a digital real-time low-loss quadrangle current mode(QCM) control implementation, which satisfies the zero-voltage-switching (ZVS) requirements, is proposed. With the QCM control method, the FSBB converter efficiency can be further increased by reducing the inductor RMS current and device switching loss compared to traditional continuous current mode(CCM) control and discontinuous current mode(DCM) control. Although the small signal model has been derived for FSBB under CCM control, the small ripple approximation that was previously used in the CCM model no longer applies in the QCM model and causing the model to be different. To aid the control system compensator design, QCM small signal model is desired. In this thesis, a small signal model for FSBB under QCM control is proposed. A 50 kW silicon carbide (SiC) based grid-interfacing converter prototype was constructed to verify the QCM control implementation and small signal model of the FSBB converter. For driving the 1.2kV SiC modules, an enhanced gate driver with fiber optic (FO) based digital communication capability was designed. Digital on-state and off-state drain-source voltage sensors and Rogowski coil-based current sensors are embedded in the gate driver to minimize the requirement for external sensors, thus increasing the power density of the converter unit. Also, Rogowski-coil-based current protection and drain-source voltage-based current protection is embedded in the gate driver to prevent SiC switching device from damage. / Master of Science / The renewable energy sector is driving the development of new distribution networks, such as DC microgrids and distributed power generation networks. One crucial component of these networks is the grid-interfacing DC-DC power converter, which can transfer power in both directions while maintaining a wide voltage range. This study evaluates various topologies and selects the four-switch buck-boost (FSBB) converter topology to meet the demands of high-power, bi-directional, and wide-range DC-DC converters. This work analyzed the operation of the FSBB converter and proposed a novel simplified quadrangle current mode (QCM) control implementation. With the QCM control method, the FSBB converter efficiency can be further improved by reducing losses compared to conventional control methods. This study also provides a small signal model, which can be used to aid the control loop compensator design where application of FSBB converter is required. A 50 kW silicon carbide (SiC) based grid-interfacing converter prototype, which was constructed to validate the proposed QCM control implementation and small signal model of the FSBB converter. As part of the converter unit,the enhanced gate driver design and implementation is presented in this thesis. This gate driver is designed with fiber optic-based digital communication, drives the wide bandgap SiC modules. The gate driver also features embedded digital on-state and off-state drain-source voltage sensors and non-intrusive current sensors to minimize external sensor requirements, thereby increasing the power density of the converter unit. The gate driver also incorporates high bandwidth current protection and drain-source voltage-based current protection to protect the SiC switching device from damage.

Substation apparatus failure plays a major role in reliability of power delivery systems. Traditionally, most utilities perform regular maintenance in order to prevent equipment breakdown. Condition-based maintenance strategy monitors the condition of the equipment by measuring and analyzing key parameters and recommends optimum maintenance actions. Equipment such as transformers and standby batteries which are valuable and critical assets in substations has attracted increased attentions in recently years. An automated monitoring and diagnosis tool for power transformers based on dissolved gas analysis, ANNEPS v4.0, was developed. The new tool extended the existing expert system and artificial neural network diagnostic engine with automated data acquisition, display, archiving, and alarm notification functions. This thesis also studied substation batteries types and failure mode and surveyed the market of current on-line battery monitors. A practical battery monitoring system architecture was proposed. Analysis rules of measured parameters were developed. The above study and results can provide basics for further designing of a simple battery monitoring system in industry applications. / Master of Science

This master’s thesis is divided into two logical parts. The first part contains theory of calculation of steady state and short-circuits conditions within 110 kV distribution network. Newton’s method and short-circuit current calculation is also explained here. It also deals with classification and aftereffects of transient performance occurring in power networks. The second part contains practical calculation of steady flow and short-circuit conditions at parallel operation of transformers T403 and T402 in 400/110 kV transformer stations Sokolnice and Otrokovice. This calculation is done with program used by system operators called SINAUT Spectrum and consequently analyzed. This part also contains brief description of substations from this region.

I en fördelarstation i Ellevios elnät i Stockholm har en viktig konfigurationsfil försvunnit. Filen används för att beskriva styr- och kommunikationssystemet för övervakning och fjärrmanövrering av stationen från en driftcentral. Dessutom behöver operativsystemet på en enhet i kommunikationssystemet uppdateras. Det misstänks att konfigurationsfilen som har försvunnit behövs för att genomföra uppdateringen. Det visar sig att konfigurationsfilen inte behövs för att genomföra uppdateringen av operativsystemet. Två metoder utvecklas därför, en för att genomföra uppdateringen av kommunikationsenheten, och en för att återskapa konfigurationsfilen. Den första metoden beskriver hur operativsystemet på en Remote Terminal Unit i ABB:s RTU500-serie kan uppdateras från firmwareversion 11 till version 12. Den andra metoden beskriver hur en fullständig konfigurationsfil, i form av en Substation Configuration Description (SCD) kan återskapas för stationen. Den senare metoden utvecklas specifikt för den enskilda stationen, men skulle kunna vidareutvecklas för att återskapa SCD-filen i fler stationer där samma problem idag finns. Metoden för att genomföra uppdatering av operativsystemet används framgångsrikt för att genomföra själva uppdateringen. Metoden för att återskapa konfigurationsfilen testas genom att en konfiguration för en ny kommunikationsenhet genereras baserat på den återskapade konfigurationen.  Genom att tillämpa dessa metoder kan tillförlitligheten för styr- och kommunikationssystem med IEC 61850-teknologi förbättras. Detta kan leda till ökad tillförlitlighet vid elleverans, eftersom kommunikationssystemet används för att övervaka elnätet och hantera fel genom fjärrstyrning. Detta minskar behovet av fysiska besök till stationen. Rapporten är ett examensarbete för programmet Högskoleingenjör i elektroteknik. Examensarbetet utfördes under våren 2023 på företaget Omexom Sweden. / In a distribution substation in Ellevio's power grid in Stockholm, an important configuration file has gone missing. The file is used to describe the control and communication system for monitoring and remote operation of the substation from a control centre. Additionally, the operating system on a device within the communication system needs to be updated. It is suspected that the missing configuration file is required to perform the update. It turns out that the configuration file is not needed to carry out the operating system update. As a result, two methods are developed: one for performing the update of the communication unit and another for recreating the configuration file. The first method describes how the operating system on a Remote Terminal Unit in ABB’s RTU500 series can be updated from firmware version 11 to version 12. The second method explains how a complete configuration file, in the form of a Substation Configuration Description (SCD) can be recreated for the substation. Although the latter method is specifically tailored for the individual substation, it could be further refined to recreate the SCD file in several other stations with the same issue. The method for performing the operating system update is successfully utilized to carry out the update itself. The method for recreating the configuration file is tested by generating a configuration for a new communication unit based on the reconstructed configuration. By implementing these methods, the reliability of the IEC 61850-based control and communication system can be enhanced. This can lead to improved reliability of power delivery since the communication system is used to monitor the power grid and manage faults through remote control. Thereby, the need for physical visits to the substation is reduced. The report is a thesis for the Bachelor program in Electrical Engineering. The thesis was carried out during the spring of 2023 at the company Omexom Sweden.

[pt] Em geral, as subestações são projetadas com transformadores em paralelo, operando a meia carga, para assegurar continuidade no fornecimento de energia mesmo que um transformador do grupo falhe. Contudo, essa prática implica em custos elevados, especialmente no que diz respeito ao arranjo de subestações. Uma solução alternativa é a utilização de estoques compartilhados de transformadores reservas e unidades de subestações móveis, que devem atender a um grupo de subestações com as mesmas características elétricas. Neste contexto, esta tese propõe a utilização temporária de unidades de subestações móveis, que devem atuar para atender à demanda de energia enquanto o transformador reserva é instalado. Essa estratégia aumenta a confiabilidade do sistema e reduz os custos operacionais e de investimento para as concessionárias de energia. No entanto, o sucesso dessa abordagem está intrinsecamente ligado ao dimensionamento e localização adequada dos estoques. Para que bons resultados sejam alcançados, é preciso dimensionar os estoques de forma que não haja investimento desnecessário ou um número insuficiente de equipamentos, e considerar pontos estratégicos de armazenamento, de forma que o tempo de deslocamento dos equipamentos sobressalentes até o ponto de falha garanta a minimização dos custos associados. Posto isso, esta tese apresenta duas metodologias de otimização baseadas em simulação Monte Carlo e Algoritmo Genético: uma para dimensionar o número de transformadores reservas e unidades de subestações móveis por ano; e outra para posicionar de forma adequada tais equipamentos em subestações com capacidade de armazenamento. Ambos os métodos foram aplicados a um grupo de transformadores de duas concessionárias reais, visando demonstrar a capacidade da metodologia de encontrar um conjunto de soluções factíveis do ponto de vista técnico e econômico. / [en] In general, substations are designed with transformers in parallel, operating at half load, to ensure continuity of power supply even if a transformer in the group fails. However, this practice involves high costs, especially with regard to the arrangement of substations. An alternative solution is the use of shared stocks of reserve transformers and mobile substation units, which must serve a group of substations with the same electrical characteristics. In this context, this thesis proposes the temporary use of mobile substation units, which must act to meet the energy demand while the reserve transformer is installed. This strategy increases system reliability and reduces operational and investment costs for electric utilities. However, the success of this approach is intrinsically linked to the proper sizing and location of stocks. For good results to be achieved, it is necessary to size stocks so that there is no unnecessary investment or an insufficient number of equipment, and consider strategic storage points, so that the time taken to move the spare equipment to the point of failure minimizes the associated costs. Thus, this thesis presents two optimization methodologies based on Monte Carlo simulation and Genetic Algorithm: one to size the number of spare transformers and mobile substation units per year; and another to properly locate such equipment in substations with storage capacity. Both methods were applied to a group of transformers from two real utilities, aiming at proving the method s ability to find a set of feasible solutions from a technical and economic point of view.

O projeto de malhas de aterramento requer o cálculo da resistência de aterramento e dos potenciais na superfície do solo. Quando o método das imagens é utilizado para este cálculo o modelo típico do solo é uma estratificação horizontal em 2 camadas. A extensão do método das imagens para solos com múltiplas camadas horizontais apresenta problemas numéricos importantes, de forma que a técnica de imagens complexas foi utilizada para permitir este cálculo, porém restringindo a posição dos eletrodos à primeira camada. Este trabalho objetiva a aplicação do método de imagens complexas a eletrodos situados em qualquer camada de solos com estratificação horizontal, deduzindo as funções kernel para posições arbitrárias da fonte e do objeto e determinando os resíduos e pólos das imagens utilizando a decomposição em autovalores e autovetores. Foi desenvolvido um programa que calcula a resistência de aterramento e os potenciais na superfície do solo para solos com até 4 camadas. Foram realizadas comparações com outros trabalhos publicados e os resultados obtidos permitem validar o uso do programa para esta aplicação. / Grounding grid design requires both ground resistance and surface potential. Traditional method of images restricts this calculation to two layer soils. Complex image method allows calculation of both resistance values and potentials at the soil surface, in multilayer soils with horizontal stratification, without grounding grid position limitation. This work presents a complete methodology for calculation of safety aspects of grounding grid design, validating results by comparison with published previous work.