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

abstract: Optical Instrument Transformers (OIT) have been developed as an alternative to traditional instrument transformers (IT). The question "Can optical instrument transformers substitute for the traditional transformers?" is the main motivation of this study. Finding the answer for this question and developing complete models are the contributions of this work. Dedicated test facilities are developed so that the steady state and transient performances of analog outputs of a magnetic current transformer (CT) and a magnetic voltage transformer (VT) are compared with that of an optical current transformer (OCT) and an optical voltage transformer (OVT) respectively. Frequency response characteristics of OIT outputs are obtained. Comparison results show that OITs have a specified accuracy of 0.3% in all cases. They are linear, and DC offset does not saturate the systems. The OIT output signal has a 40~60 μs time delay, but this is typically less than the equivalent phase difference permitted by the IEEE and IEC standards for protection applications. Analog outputs have significantly higher bandwidths (adjustable to 20 to 40 kHz) than the IT. The digital output signal bandwidth (2.4 kHz) of an OCT is significantly lower than the analog signal bandwidth (20 kHz) due to the sampling rates involved. The OIT analog outputs may have significant white noise of 6%, but the white noise does not affect accuracy or protection performance. Temperatures up to 50oC do not adversely affect the performance of the OITs. Three types of models are developed for analog outputs: analog, digital, and complete models. Well-known mathematical methods, such as network synthesis and Jones calculus methods are applied. The developed models are compared with experiment results and are verified with simulation programs. Results show less than 1.5% for OCT and 2% for OVT difference and that the developed models can be used for power system simulations and the method used for the development can be used to develop models for all other brands of optical systems. The communication and data transfer between the all-digital protection systems is investigated by developing a test facility for all digital protection systems. Test results show that different manufacturers' relays and transformers based on the IEC standard can serve the power system successfully. / Dissertation/Thesis / Ph.D. Electrical Engineering 2010

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

The ability of typical utility meters and advanced meters including sub-circuit metering to disaggregate residential electric loads and determine what appliances a homeowner is using at a given time in investigated. The basics of residential electricity systems, instrumentation options, and characteristics of selected residential loads are presented. This information informs a discussion on present and future disaggregation algorithms. The conclusions highlight the importance of reactive power and current harmonics in determining power consumed and identifying modern electrical devices, and raise concerns related to the ability of typical 15 minute interval utility smart meters to disaggregate loads. / text

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

This thesis presents and describes new global trends among build and operation of datacenters. Further it contains practical application of particular examples, and the theory is supplemented by new findings from given field.

The world of power systems is ever changing; ever evolving. One such evolution was the advent of Phasor Measurement Units (PMUs). With the introduction of PMUs in the field, power system monitoring and control changed for the better. Innovative and efficient algorithms that used synchrophasors came to be written. To make these algorithms robust, it became necessary to remove errors that crept into the power system with time and usage. Thus the process of calibration became essential when practical decisions started being made based on PMU measurements. In the context of this thesis ‘calibration’ is the method used to estimate a correction factor which, when multiplied with the respective measurement, negates the effect of any errors that might have crept into them due to the instrument transformers located at the inputs of a PMU or the PMU device itself. Though this thesis mainly deals with the calibration of instrument transformers, work has been done previously for calibrating other components of a power system. A brief description of those methods have been provided along with a history on instrument transformer calibration. Three new methodologies for instrument transformer calibration have been discussed in details in this thesis. The first method describes how only voltage transformers can be calibrated by placing optimal number of good quality voltage measurements at strategic locations in the grid, in presence of ratio errors in the instrument transformers and Gaussian errors in the PMUs. The second method provides a way to calibrate all instrument transformers (both current and voltage) in presence of only one good quality voltage measurement located at the end of a tie-line. This method assumes that all the instrument transformers have ratio errors and the PMUs have quantization errors. The third method attains the same objective as the second one, with the additional constraint that the data obtained from the field may be contaminated. Thus, the third method shows how calibration of all the instrument transformers can be done with data that is intermittent and is therefore, the most practical approach (of the three) for instrument transformer calibration. / Master of Science

[pt] Esta Dissertação de Mestrado apresenta uma metodologia para analisar transformadores para instrumentos (TI) em geral, e vários tipos de transformadores de corrente (TC-s) para medição. O funcionamento e as características dos transformadores de potencial (TP-s) e dos TC-s estão sendo analisados, usando-se as ferramentas tradicionais (circuito equivalente e representação fasorial). O tratamento generalizado facilita a comparação entre TP-s e TC-s e a análise qualitativa dos parâmetros que influenciam os erros de relação e de ângulo de fase.Após verificação geral, quatro tipos de TC-s estão sendo estudados detalhadamente. Para analisar construções eletromagnéticas mais complexas, um método não tradicional está sendo aplicado. Usando-se as representações fasoriais,realiza-se o cálculo baseando-se nas equações elétricas e nas equações magnéticas. O erro complexo do TC é o resultado das soluções destas equações, e vem expresso em função dos parâmetros de construção. Os resultados facilitam comparar o desempenho de vários tipos de TC-s existentes e/ou a serem projetados. Um programa de simulação, utilizando a linguagem C no ambiente LabWindows/CVI - C for Virtual Instrumentation (National Instruments), foi desenvolvido com base nas equações para o cálculo do erro. O programa analisa o comportamento de 4 tipos de TC-s, existentes e/ou a serem projetados, quanto ao erro de relação e ao ângulo de fase. A partir do tipo de material, da dimensão do núcleo e do tipo de enrolamentos, em modo interativo, pode-se escolher várias combinações dos parâmetros em etapas repetidas. A eficiência do método aplicado foi verificada e comprovada. Os resultados são coerentes e quando usados no programa de simulação, resultam em um novo método para analisar, projetar ou escolher um TC para uma finalidade específica. / [en] This dissertation for a master degree presents a methodology to analyse Instrument Transformers in general terms and several types of Current Transformers (CT`s) for measurements, in details.At first, operation and characteristics of Potential Transformers (PT` s) and that of CT` s are analysed, using traditional tools (as equivalent circuits and fasorial representation). The generalised treatment facilitates the comparison between PT` s and CT` s as well as a qualitative analysis of the parameters influencing the ratio and phase errors. After giving a general view, four types of CT` s are studied in details. To analyse complex electromagnetic constructions, a non-traditional method is applied. By using fasorial representations, calculus is based on defining separate groups of electrical and magnetic equations to describe a device. The result of the solution of this set of equations is the complex error of the CT, which is being expressed exclusively in terms of parameters of the construction. The results facilitate the comparison of the performance of various types of CT` s, that exist or are to be designed. A simulation program, using language C, in the ambient of LabWindows/CVI - C for Virtual Instrumentation (National Instruments), was developed, in order to calculate the errors, based upon the equations obtained. The program is capable of specifying the parameters and analysing the characteristics of four types of CT` s, representing finally the ratio and phase errors, in terms of the variation of the current or that of the load. Characteristics of various magnet ic materials, dimensions ofstandardized toroidal cores and that of wires can be specified, stored and selected thereafter. The program facilitates experimenting with various combinations of parameters in an interactive mode and to approximate optimised constructions in iterative steps. Efficiency of the method was verified and proved. The results are coherent and when are used in the simulation program, represent a new method to analyse an existing CT or to design a new one, or to select the most adequate model for a specific purpose.

The main focus of the dissertation thesis is determine the size of the fastening screw connection and fastening torque of the connection, which will be applied during assembly of the instrument current transformers and sensors. The large part of thesis is an experimental measurement of the proposed configurations of connections and modelling (simulating) certain model of connections in Ansys and SolidWorks analysis programs. The result of the dissertation will be design of tightening of the connection according to transient resistance and thermal losses.

The diploma thesis deals with conventional transformers and current and voltage sensors. The first half of thesis describes mainly the basic concepts and accuracy classes of these converters used in electrical substations. The emphasis is given primarily on the differences. In the second half of thesis is presented an exact type of converters, which are installed in the substation Medlánky. There is an analysis of measured data from long – term monitoring from this substation and comparing the results from conventional transformers compared to the results from more modern sensors.