Instrument transformers are a crucial component of power system protection. They supply the protection system with scaled-down replicas of current and voltage signals present in a power network to the levels which are safe and practical to op- erate with. The conventional instrument transformers are based on electromagnetic coupling between the power network on the primary side and protective devices on the secondary. Due to such a design, instrument transformers insert distortions in the mentioned signal replicas. Protective devices may be sensitive to these distortions. The inuence of distortions may lead to disastrous misoperations of protective devices. To overcome this problem, a new instrument transformer design has been devised: optical sensing of currents and voltages. In the theory, novel instrument transform- ers promise a distortion-free replication of the primary signals. Since the mentioned novel design has not been widely used in practice so far, its superior performance needs to be evaluated. This poses a question: how can the new technology (design) be evaluated, and compared to the existing instrument transformer technology? The importance of this question lies in its consequence: is there a necessity to upgrade the protection system, i.e. to replace the conventional instrument transformers with the novel ones, which would be quite expensive and time-consuming? The posed question can be answered by comparing inuences of both the novel and the conventional instrument transformers on the protection system. At present, there is no systematic approach to this evaluation. Since the evaluation could lead to an improvement of the overall protection system, this thesis proposes a comprehensive and systematic methodology for the evaluation. The thesis also proposes a complete solution for the evaluation, in the form of a simulation environment. Finally, the thesis presents results of evaluation, along with their interpretation.

A dissertation submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering. / The sudden failure of oil paper-insulated current transformers has become a problem of considerable concern due to the cost of the resulting destruction, and danger to personnel. The aim of the dissertation is. to determine the most suitable method of detecting lncipient faults in current transformers, test this method on an experimental current transformer, and finally implement this technique in a low cost on-line monitor. A literature survey indicated that hydrogen gas-in-oil on-line monitoring would be the most suitable technique.(Abbreviation abstract) / Andrew Chakane 2019

A dissertation submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering / The sudden failure of oil paper-insulated current transformers has become a problem of considerable concern due to the cost of the resulting destruction, and danger to personnel. The aim of the dissertation is to determine the most suitable method of detecting incipient faults in current transformers, test this method on an experimental current transformer, and finally implement this technique in a low cost on-line monitor. A literature survey indicated that hydrogen gas-in-oil on-line monitoring would be the most suitable technique.(Abbreviation abstract) / Andrew Chakane 2019

Master's thesis deals with use of electronic instrument transformers (sensors) in the protection system in medium-voltage substation. Substation consists of 2 incoming feeders, 2 outgoing feeders for motors, 2 outgoing feeders for power transformers, measuring, bus coupler and bus riser feeder. Incoming feeders are connected to distribution system E.ON by cable lines which were proposed. Protected machines (power transformers and motors with rated power) are connected to switchgear panels of UniGear ZS1 type by cable lines too. Proposed protection system is based on the short-circuit conditions, standard CSN 33 3051 recommendations as well as theoretical backgrounds acquired from technical papers and other publicated literature according to the bibliography. For selected protection functions are defined their parameters. Control, monitoring and protection functions provides REF 542plus relay. Consequently, secondary tests which are part of the commissioning, are given in the practical part of thesis. Secondary tests were performed by relay test system FREJA 300 by Megger. Results of tests are displayed in tripping characteristics.

Detta examensarbete är utfört på uppdrag av Rejlers Ingenjörer i Göteborg. Syftet med arbetet är att genom en projektering övergripande presentera utförandet, komponenter, funktioner, ekonomi och situationsplaner för två förslag på stationsutformningar i samband med en ombyggnation och utvidgning av en transformatorstation. Transformatorstationen har i nuläget två spänningsnivåer på 40 kV och 10 kV. I samband med ombyggnationen skall stationen kompletteras med ytterligare en spänningsnivå på 20 kV, för anslutning av ett antal vindkraftverk. För att anläggningen skall uppfylla grundläggande krav, utförs projekteringen genom att sortera och sammanställa relevant information från gällande föreskrifter, standarder och tekniska riktlinjer. Vidare inhämtas ytterligare information från litteratur, kataloger, produktblad och muntlig kontakt med uppdragsgivaren. I arbetet presenteras två förslag på stationsutformningar i enlighet med syftet. Stationens högspänningsapparater dimensioneras och presenteras, och dess reläskyddsfunktioner identifieras. I båda alternativen är transformatorerna placerade utomhus med en stationsbyggnad som rymmer 10 kV-, 20 kV-ställverket, ett batterirum och ett kontrollrum. Skillnaden mellan alternativen ligger främst i att ett av alternativen har ett utomhusbyggt luftisolerat 40 kV-ställverk medan det andra alternativet har ett kompaktare inomhusbyggt luftisolerat 40 kV-ställverk. Den totalt beräknade kostnaden, inklusive drift- och underhållskostnader, under en 25-årsperiod beräknas uppgå till 22,7 Mkr för utomhusalternativet och 22,4 Mkr för inomhusalternativet. Skillnaden mellan alternativen förväntas stiga till inomhusalternativets fördel, om även samhällskostnader vid avbrott vägs in i kalkylen. Rekommendationen är att transformatorstationen uppförs enligt inomhusalternativet, eftersom detta torde anses ge bäst totalekonomi, driftsäkerhet och skydd mot obehörigt tillträde. / This bachelor´s thesis is carried out on behalf of Rejlers Ingenjörer in Gothenburg. The work aims to overall present the realization of two station design proposals, including components, functions, financial aspects and plans, in connection with a reconstruction and expansion of a substation. The substation currently has two voltage levels of 40 kV and 10 kV. In connection with the reconstruction, the station is supplemented by a further voltage level of 20 kV, for connection of a number of wind turbines. For the installation to meet basic requirements, the work is performed by sorting and putting together relevant information from applicable regulations, standards and technical guidelines. Further information is obtained through additional information from literature, catalogues, product sheets and verbal contact with the job requestor. In the thesis the two station design proposals are presented in compliance with the aim. The high voltage equipment is dimensioned and presented, and the relay protection functions are identified. In both options, the transformers are located outdoors with a station building that houses 10 kV, 20 kV switchgear, a battery room and a control room. The main difference between the alternatives is that one of the options has an outdoor air insulated 40 kV switchgear, while the second one has a more compact indoor air insulated switchgear. The total estimated cost, including operation and maintenance costs, over a 25-year period is estimated at 22.7 million Swedish kronor for the outdoor option and 22.4 million Swedish kronor for the indoor alternative. The difference in costs is expected to rise to the advantage of the indoor option if social costs during a power failure also are taken into account in the calculation. It is recommended that the substation be built according to the indoor option, since this is considered to provide the best overall economy, safety of operation and protection against unauthorized access.

Thesis (MScEng)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: The bandwidth of standard HV measurement devices such as capacitive voltage transformers is too limited in order to measure wideband phenomena. This thesis is concerned with the investigation into a non- intrusive HV transient voltage measurement facility using standard substation HV current transformers (CI's) configured in a transconductance topology. The sensing, summation and integration of the CT capacitive earth currents are investigated. This thesis also reports on the development of a optically isolated link using optical fibre for signal transfer and a computer based data acquisition system. / AFRIKAANSE OPSOMMING: Standaard hoogspannings (HS) meettoerusting soos kapasitiewe spannmgs transformators het beperkte bandwydte vir die meet van wyeband verskynsels. Hierdie tesis handel oor die implementering van 'n HS meetstelsel wat op meinbrekende wyse oorgangsverskynsels meet deur middel van HS stroomtransformators wat in 'n transkonduktansie topologie gekonfigureer is. Die meet, sommasie en integrasie van kapasitoewe grondstrome word ondersoek. Hierdie tesis doen ook verslag aangaande die ontwikkeling van 'n optiese geisoleerde koppelvlak wat gebruik word vir seinoordrag en 'n rekenaar gebasseerde data versamelaar. / pdv201406

The introduction of synchrophasor technology to the realm of power systems has presented a myriad of novel approaches to age-old problems. In this thesis, the questions of instrument transformer calibration and transmission line parameter estimation have been examined. With synchrophasors offering real-time data for analysis, a solution to each individual problem seems feasible. A quandary however arises due to the fact that calibration methods depend on accurate knowledge of line parameters, and estimation of these parameters depend on calibrated measurements. Traditional methods of determining the parameters may not be the most accurate due to a variety of fluctuations possible on the system, which is why real-time estimation could prove beneficial. This work analyzes each problem and a feasible solution and proposes a method to achieve transducer calibration as well as parameter estimation together, while employing synchronized phasor measurements. / Master of Science / Synchrophasor Measurement Units (PMUs) provide the magnitude and angle of the quantity being measured, along with GPS time synchronization. Voltage, current and frequency data can be sent to a central control centre at the rate of 30 or 60 times per second. With a sufficient number of PMUs deployed on the electric grid, system operators now have available essentially a ‘snapshot’ of the system, which aids to monitor the grid, predict abnormal conditions as well as quickly identify troubled areas and accordingly take remedial actions. In order to facilitate the safe and reliable operation of the electric power grid, there are numerous devices that monitor quantities such as voltage, current, frequency etc. Most of these devices however are incapable of handling high levels of voltage and currents that are common to the power network. Instrument transformers (IT) are used to step down the measured quantities to much lower magnitudes that can then be analyzed by downstream devices. Each instrument transformer has a specified transformation ratio. For example, a voltage transformer with a transformation ratio of 100:1 would step down 500V to 5V. With time, these ITs may experience wear which might lead to degradation of its ratio, which would in turn be detrimental for applications relying on accurate measurements. Therefore routine calibration of ITs is desired. Traditional methods of calibration however involve taking the device out of service temporarily. As one can imagine, this is cost, labour and time intensive. With the availability of PMU data, it is now possible to perform calibration of these devices without having to take the device offline, provided we have accurate knowledge of the transmission line parameters. The parameters of a transmission line include the resistance, reactance and susceptance of the line and depend on the type of conductor used, the length and ambient temperature. Therefore seasonal and daily temperature variations can cause changes in the line parameters. With PMU data, we now have the capability to estimate these parameters, so that we have the most accurate idea of the present parameters. However for this, calibrated voltages and currents are required. Herein we face a quandary: we need to calibrate the ITs, which require accurate line parameters, but to estimate the current line parameters we need calibrated voltages and currents. This is the problem this thesis addresses. First, methods to perform both tasks, i.e. instrument transformer calibration as well as line parameter estimation using PMU measurements are analyzed. Finally an iterative method is proposed that can be applied to solve both problems together.

As elevadas perdas existentes no setor elétrico tem causado preocupação nas empresas de distribuição, aliadas ainda a necessidade crescente de um desenvolvimento econômico sustentável. Neste cenário a calibração periódica dos instrumentos destinados a medição (entre eles os transformadores de instrumentos) tornam-se essenciais e tais procedimentos encontram-se previstos no novo modelo de operação do setor elétrico. Porém, as dificuldades logísticas e operacionais de transporte a laboratórios metrológicos credenciados dificultam a execução de tais serviços. As técnicas e métodos desenvolvidos nesse trabalho visam a implementação de uma unidade eletrônica capaz de aquisitar e processar dados provenientes de transformadores de instrumentos, de natureza indutiva (denominado de convencional) e ópticos, bem como seus subsistemas de apoio, como ferramentas de medição e calibração portátil, móvel, para execução dos serviços metrológicos in situ nos ambientes das subestações e cabines primárias. Estes serviços, apesar de estarem em estágio incipiente, são de extremo interesse para empresas de energia elétrica. Este projeto está baseado no estado da arte de componentes da eletrônica analógica e digital, onde destacam-se conversores analógico/digital (A/D), microprocessadores, osciladores, FPGA e técnicas computacionais para processamento digital de sinais. São apresentadas as formas de implementação tanto em hardware como em software para esta unidade eletrônica de forma a atender aos requisitos funcionais especificados e às normas do INMETRO e normas internacionais equivalentes para aplicações metrológicas. A validação é baseada em testes comparativos dos fasores na frequência fundamental dos sinais obtidos, analisando os valores de amplitude (para cálculo de erro de relação) e de fase ( para cálculo de erro de fase) entre transformadores ópticos e convencionais, sendo que estes últimos podem ser de referência ou não. / The high losses in the electricity sector have caused concern in distribution companies, together with the growing need for sustainable economic development. In this scenario the periodic calibration of instruments intended for measurement (including instrument transformers) become essential and such procedures are provided for in the new model of operation of the electric sector. However, the logistical and operational difficulties of transportation to accredited metrological laboratories make it difficult to perform such services. The techniques and methods developed in this work are aimed at the implementation of an electronic unit capable of acquiring and processing data from instrument transformers of an inductive (conventional) and optical nature, as well as its supporting subsystems, such as portable and mobile measuring and calibration tools for the execution of on-site metrological services in the substations and primary cabins. These services, although in an incipient stage, are of extreme interest to electric energy companies. This project is based on the state-of-the-art components of analog and digital electronics, including analog/digital (A/D) converters, microprocessors, oscillators, FPGA and computational techniques for digital signal processing. The forms of implementation in both hardware and software for this electronic unit are presented in order to meet the functional requirements specified and the standards of the Instituto Nacional de Metrologia (INMETRO) and equivalent international standards for metrological applications. The validation is based on comparative tests of the phasors at the fundamental frequency of the obtained signals, analyzing the amplitude (for ratio error calculation) and phase (for phase error calculation) between optical and conventional transformers, the last one can be reference or not.

As elevadas perdas existentes no setor elétrico tem causado preocupação nas empresas de distribuição, aliadas ainda a necessidade crescente de um desenvolvimento econômico sustentável. Neste cenário a calibração periódica dos instrumentos destinados a medição (entre eles os transformadores de instrumentos) tornam-se essenciais e tais procedimentos encontram-se previstos no novo modelo de operação do setor elétrico. Porém, as dificuldades logísticas e operacionais de transporte a laboratórios metrológicos credenciados dificultam a execução de tais serviços. As técnicas e métodos desenvolvidos nesse trabalho visam a implementação de uma unidade eletrônica capaz de aquisitar e processar dados provenientes de transformadores de instrumentos, de natureza indutiva (denominado de convencional) e ópticos, bem como seus subsistemas de apoio, como ferramentas de medição e calibração portátil, móvel, para execução dos serviços metrológicos in situ nos ambientes das subestações e cabines primárias. Estes serviços, apesar de estarem em estágio incipiente, são de extremo interesse para empresas de energia elétrica. Este projeto está baseado no estado da arte de componentes da eletrônica analógica e digital, onde destacam-se conversores analógico/digital (A/D), microprocessadores, osciladores, FPGA e técnicas computacionais para processamento digital de sinais. São apresentadas as formas de implementação tanto em hardware como em software para esta unidade eletrônica de forma a atender aos requisitos funcionais especificados e às normas do INMETRO e normas internacionais equivalentes para aplicações metrológicas. A validação é baseada em testes comparativos dos fasores na frequência fundamental dos sinais obtidos, analisando os valores de amplitude (para cálculo de erro de relação) e de fase ( para cálculo de erro de fase) entre transformadores ópticos e convencionais, sendo que estes últimos podem ser de referência ou não. / The high losses in the electricity sector have caused concern in distribution companies, together with the growing need for sustainable economic development. In this scenario the periodic calibration of instruments intended for measurement (including instrument transformers) become essential and such procedures are provided for in the new model of operation of the electric sector. However, the logistical and operational difficulties of transportation to accredited metrological laboratories make it difficult to perform such services. The techniques and methods developed in this work are aimed at the implementation of an electronic unit capable of acquiring and processing data from instrument transformers of an inductive (conventional) and optical nature, as well as its supporting subsystems, such as portable and mobile measuring and calibration tools for the execution of on-site metrological services in the substations and primary cabins. These services, although in an incipient stage, are of extreme interest to electric energy companies. This project is based on the state-of-the-art components of analog and digital electronics, including analog/digital (A/D) converters, microprocessors, oscillators, FPGA and computational techniques for digital signal processing. The forms of implementation in both hardware and software for this electronic unit are presented in order to meet the functional requirements specified and the standards of the Instituto Nacional de Metrologia (INMETRO) and equivalent international standards for metrological applications. The validation is based on comparative tests of the phasors at the fundamental frequency of the obtained signals, analyzing the amplitude (for ratio error calculation) and phase (for phase error calculation) between optical and conventional transformers, the last one can be reference or not.

Desde seu lançamento, em 2002, a Norma IEC 61850 vem evoluindo para se tornar o padrão adotado nos Sistemas de Automação de Subestações. Dentre seus vários aspectos, destacam- se os serviços de tempo real, que permitem a implementação de funções de automação e de proteção dentro da subestação através da troca de mensagens específicas entre Dispositivos Eletrônicos Inteligentes através de um barramento digital de rede de dados. O objetivo central deste trabalho é explorar algumas das questões que envolvem a implementação de uma classe de serviços de tempo real: a transmissão de valores amostrados através de Serviços SMV, definidos pela Norma IEC 61850-9. Primeiramente, apresenta-se um breve resumo das principais características da Norma IEC 61850 que possibilitam o atendimento dos três requisitos por ela estabelecidos como base: a interoperabilidade entre dispositivos de diferentes fabricantes, a versatilidade na configuração e reconfiguração do Sistema de Automação da Subestação, e a possibilidade de implementação de novas tecnologias. Em seguida, explora-se com maior profundidade todos os aspectos relevantes à implementação dos Serviços SMV. Devido à complexidade deste assunto, o autor propõe abordá-lo sob a ótica de cinco tópicos interdependentes: variações da Norma IEC 61850-9, confiabilidade do barramento de processo, sincronismo de tempo, análise da qualidade da medição e segurança cibernética. Com base nos resultados apresentados neste estudo, propõem-se duas plataformas, um protótipo de Transformador de Potencial Óptico e um protótipo de Relé de Proteção Diferencial para transformadores de potência, com o objetivo de explorar alguns dos aspectos pertinentes à implementação de um barramento de processo de acordo com a Norma IEC 61850-9. Também foram realizados testes de geração e transmissão de mensagens contendo valores de amostras de tensão/corrente do sistema elétrico (denominadas de SV Messages) com a finalidade de implementá-las de fato e avaliar as ferramentas de mercado disponíveis. Por fim foi proposto um modelo para a simulação do sistema de potência em conjunto com a rede de comunicação utilizando o programa Matlab/Simulink. O autor espera que este trabalho contribua para esclarecer os vários conceitos envolvidos na implementação do barramento de processo definido pela Norma IEC 61850-9, auxiliando na pesquisa e no desenvolvimento de novas ferramentas e dispositivos, e no aprimoramento da Norma IEC 61850. / Since its introduction, in 2002, the IEC 61850 Standard has been evolved to become the standard adopted in Substation Automation Systems. Among its various aspects it can be highlighted the real-time services, which allows the implementation of automation and protection functions within the substation by exchanging specific messages between Intelligent Electronic Devices via a digital data bus network. The main objective of this text is to explore some issues about the implementation of one class of real-time services: the transmission of sampled values through SMV Services, defined by IEC 61850-9 Standard. First, it is presented a brief summary of the main features of IEC 61850 Standard which allows it to meet the three main requirements on this standard: interoperability between devices from different manufacturers, versatility in configuration and reconfiguration of Substation Automation System, and possibility of implementation of new technologies. Next, it is explored, with more details, all aspects involved in the implementation of SMV Services. Due to the complexity of this subject, the author proposes approaches it from the perspective of five interdependent topics: variations of IEC 61850-9 Standard, process bus reliability, time synchronism, analysis of measurement quality, and cyber security. Based on results presented two platforms are proposed, an Optical Voltage Transformer prototype and a Differential Protection Relay prototype for power transformers, in order to explore some of aspects related to the implementation of a process bus according to IEC 61850-9 Standard. It was executed also some tests of generation and transmission of messages containing samples values of voltage/current from power system (referred as SV Messages) in order to implement them in fact, and to evaluate available market tools. At the end it is propoused a model for simulation of power system and network communication using Matlab/Simulink software. The author hopes this work may contribute to clarify the various concepts involved in the implementation of a process bus according to IEC 61850-9 Standard, aiding in research and development of new tools and devices, and improvement of IEC 61850 Standard.