Academic literature on the topic 'Medium Voltage measurement'

Measurements of medium and high voltages in a power grid are normally performed with large and bulky voltage transformers or capacitive dividers. Besides installation problems, these devices operate in a relatively narrow frequency band, which limits their usability in modern systems that are saturated with power electronic devices. A sensor that can be installed directly on a wire and can operate without a galvanic connection to the ground may be used as an alternative voltage measurement device. This type of voltage sensor can complement current sensors installed on a wire, forming a complete power acquisition system. This paper presents such a sensor. Our sensor is built using two dielectric elements with different permeability coefficients. A finite element method simulation is used to estimate the parameters of a constructed sensor. Besides simulations, a laboratory model of a sensor was built and tested in a medium-voltage substation. Our results provide a proof of concept for the presented sensor. Some errors in voltage reconstruction have been traced to an oversimplified data acquisition and transmission system, which has to be improved during the further development of the sensor.

The features of a Power Quality measurement system which includes both voltage and current transducers and a self-developed measuring instrument are described. The system is intended for measurements in substations at medium voltage level. A Rogowski coil and a voltage divider are the used transducers, whereas the measuring instrument is based on a Reconfigurable I/O-FPGA system with embedded software. Attention is focused on the procedures adopted for the characterization of the voltage and current sensors, which are carried out taking into account the expected on-site measurement conditions. An example of use of the systems for measurement of some PQ parameters in a private substation which connects an industrial load and two photo-voltaic generation plants to the public MV voltage network is presented, together with the associated voltage and current uncertainty budget. By making use of the results obtained in the characterization phase, the current and voltage measurement uncertainty can be reduced.

The evolution of modern power distribution systems into smart grids requires the development of dedicated state estimation (SE) algorithms for real-time identification of the overall system state variables. This paper proposes a strategy to evaluate the minimum number and best position of power injection meters in radial distribution systems for SE purposes. Measurement points are identified with the aim of reducing uncertainty in branch power flow estimations. An incremental heuristic meter placement (IHMP) approach is proposed to select the locations and total number of power measurements. The meter placement procedure was implemented for a backward/forward load flow algorithm proposed by the authors, which allows the evaluation of medium-voltage power flows starting from low-voltage load measurements. This allows the reduction of the overall costs of measurement equipment and setup. The IHMP method was tested in the real 25-bus medium-voltage (MV) radial distribution network of the Island of Ustica (Mediterranean Sea). The proposed method is useful both for finding the best measurement configuration in a new distribution network and also for implementing an incremental enhancement of an existing measurement configuration, reaching a good tradeoff between instrumentation costs and measurement uncertainty.

Recent trends in power system design such as an increasing share of renewable energy sources and smart grids are creating different subsystem interactions that require proper investigation, understanding, describing and estimating global system stability through impedance-admittance measurement and identification. This paper proposes and presents the cascaded H-bridge multilevel inverter topology for perturbation injection converter and impedance-admittance measurement. The methodology of impedance-admittance measurement is explained together with different measurements requirements. Performance and suitability of this topology for impedance-admittance measurement is evaluated through simulations. Preliminary design principles are given for the converter. System level feasibility of the solution is proposed as a main result of the work.

The distribution network is experiencing a massive deployment of intelligent electronic devices (IEDs) such as energy meters, protective devices, and phasor measurement units (PMUs). This phenomenon resulted, on the one hand, in (i) the availability of distributed measurement systems capable of monitoring and collecting measurements from the distribution network, and (ii) increasing awareness of the system operator about the status of the network. On the other hand, such a significant number of devices require to be characterized, over the years, and assessed in both sinusoidal and distorted conditions. However, the characterization process may require a huge investment of money and time considering the low availability of reference instruments and accredited laboratories. To this purpose, this paper presents a simple and fast test procedure, performed with cheap and low-voltage instrumentation, to characterize two off-the-shelf low-power medium-voltage sensors in the power quality frequency range. In detail, the paper describes the measurement setup developed for the characterization and the performed tests. In addition, the method was also reproduced with reference equipment for validation purposes. Lastly, for both tests, an uncertainty evaluation was performed to quantify the goodness of the proposed method. From the results, it is possible to appreciate that the designed cheap and simple test can achieve as accurate results as those of a sophisticated and expensive equipment.

Nickel (Ni) is a highly toxic heavy metal because nickel can accumulate and poison aquatic biotic components, therefore it’s levels must be determined with certainty. In this study, nickel metal measurements were made using the cyclic voltammetry method. Several measurement parameters, including voltage range, scan rate, and pH, were tested in this study to improve sensitivity and accuracy. This is done to achieve the best possible measurement conditions. The results show that the best conditions for detecting Ni ions are a voltage range of -0.75 V to -1.00 V, a scan rate of 250 mV/s, and a pH of 3. The validation test produced results in the range of 15 to 40 mM with a correlation coefficient of 0.99, detection and quantitation limits of 274.99 ppm and 916.66 ppm, respectively, and an RSD of 1.10%. As a comparison, Ni content was tested using AAS, and the Ni contents obtained by cyclic voltammetry and AAS methods were 1666.47 and 1676 ppm, respectively.

Elmont d.o.o. Krško – We have spread our main scope of the services from electrical maintenance, modifications implementations and quality control to cable testing area. The main reason for expanding our scope was to support Nuclear Power Plant Krško Cable Aging Management program and the world trend of LTE (Life Time Extension) in power plants. Scope of work – We are identifying potential downgraded conditions for safety and operational important cables in special areas (heat, water, radiation). Our main scope is visual control, and testing with analysis. For low voltage cables the main testing method is Line Resonance Analysis (LIRA). LIRA technology is based on the transmission line theory, through the estimation and analysis of the complex line impedance as a function of the applied signal frequency. We can monitor the global, progressive degradation of the cable insulation due to harsh environment conditions (high temperature, humidity, radiation) and detect local degradation of the insulation material due to mechanical impacts or local abnormal environmental conditions. For medium voltage cables we are using new methods with a power generator that uses Very Low Frequency – 0,1Hz (VLF). The main reason for this is that the measurement unit needs 500 times less energy than the unit which uses 50Hz frequency (50/0,1=500). With this power source we are performing dielectric loss measurements – Tan delta (TD) and Partial discharge measurements (PD). TD measurements show the severity of Water treeing in the measured cable. Water trees mainly come from moisture and are therefore present in cables that lie in manholes filled with water or they submerged in any other way. PD measurements show the severity of voids or other types of defects in cable insulation. These defects can arise during the manufacturing of the cable or they can arise during the installation of the cable or from an accident with the cable during the operational time.

The aim of this project is the design and the realization of a 30 kV reference voltage divider (VD) for smart grid monitoring, which will be mainly used in laboratories to characterize and calibrate the voltage transducers. The scale factor ratio error introduced by a normal voltage transducer (VT), according to technical report IEC/TR 61869-103 must be limited to a maximum of 1% up to 2nd harmonics and to a maximum of 5% up to the 50th harmonics. The maximum acceptable phase error should be no more than 18 mrad up to the 2nd harmonics and 90 mrad up to the 50th harmonics. Of course, the target for a reference voltage transducer should be much more accurate than the requirement of the standards for a normal VT. A reference voltage transducer is expected to show high accuracy also at higher frequencies, since this feature is needed in smart grids, due to the considerable amount of harmonics after the 50th harmonics even up to 10 kHz, although this peculiarity is not required by the standards for transducers in normal electrical networks. Then, in the bandwidth up to 10 kHz, the maximum target deviation from the rated scale factor for the reference VD has been selected equal to 0.05 % and the maximum phase error equal to 9 mrad. To reach such a high accuracy, there is a need for a design tool, which can model and simulate the divider with a very good accuracy. Then, this tool could be used for the design procedure of the structure and of the definition of the geometrical parameters of the reference VD, in order to realize an extremely accurate measurement device satisfying the demanding constraints mentioned above. To begin with, two methods, the Finite Element Method (FEM) and the Boundary Element Method (BEM), were examined in calculating the stray capacitance between two (physically infinite) planes. The comparison of BEM and FEM results with the analytical ones shows a better accuracy and a lower CPU simulation time in FEM rather than in BEM approach. Thus, the physical model of the reference VD has been simulated by FEM. The output of the FEM software is a matrix defining the stray capacitance network between different nodes (equipotential surfaces) of a voltage divider. This matrix is used as an input of a MATLAB program, which solves the electrical circuit of the VD. Furthermore, a small voltage divider was realized to prove the capability of this modeling approach. The measurement results of the test VD shows a good agreement with the results obtained from the theoretical method. An innovative approach was presented in the modeling of resistors, which have been divided into two parts, instead of being modeled as a single component. The important role of the resistor body modeling in calculating the stray capacitances in the VD has been highlighted. The validation procedure was repeated for a real 20 kV VD that was already available. The comparison between measurement and theoretical results confirms the validity and high accuracy of the proposed modelling approach. The research carried out up to here has been published in “IEEE Transaction on power delivery”. The realization of the numerical tool has allowed the design of the reference 30 kV VD. The first issue was to find the best configuration for the VD. It is not clear in literature what kind of configuration could be the best or what should be considered in the design and realization course. Such a lack of guidelines is the main reason that impeded the application of an optimization method in this project. In fact, the optimization process could be used for a device, which has a known and fixed configuration with a limited number of geometrical and electrical variables that can be selected in order to find the best value for the best objective function. The design realized in this project aimed also at configuring shape and structure of the divider for future optimization process. In other words, some different VD configurations and effect of different parameters variation have been deeply investigated. At the start of assessment, different kind of stray capacitances and their effect on the frequency behavior of a VD have been discussed. This subject has been investigated by introducing the equivalent circuit of a simple VD. Then the effect of modifying different kind of stray capacitances on the VD frequency behavior has been shown. Besides, the best condition for the stray capacitances that can lead to a good frequency behavior has been discussed. The initial VD design procedure was done in order to mainly understand the effect of geometrical parameters like the distances between the HV resistors and between HV and LV sections. The goal was to lower (and also balance) the stray capacitances. Then, a grounded plate has been introduced and discussed in the resistive VD with horizontally placed resistors, in the attempt of reducing and better balancing the stray capacitances. The effect of the presence and also the size of the plate has been discussed and the effect of the distances between the resistors were also studied (Section 3.3). At this stage, new circuital components have been introduced in the divider. The compensation of the low voltage (LV) side with an extra LV capacitor (CBT) is explained (this subject is explained in detail in section 3.3.7). As the next step, a Reference Voltage Divider (RVD) considering the voltage requirements (30kV) and high voltage (HV) resistors (with rated voltage of 10 kV) has been designed. The first design has been dedicated to the simplest configuration with vertically placed HV resistors. Then the geometrical parameters (distances) has been changed and the effect was studied. At the end of this part, a VD configuration with vertically placed HV resistors has been modelled and simulated. The simulation has been carried out with an accurate model including all the details of the components available for the VD realization like, for instance, insulation supports, resistors and pillars. Design simulations show very good results that comply the uncertainty limitations of a reference VD. However, there was a drawback in that first design configuration. Its size was quite large compared to the similar measurement devices in this voltage range. Despite this fact, the finalized RVD was realized and its frequency behavior was measured using two digitizers at the low voltage side. Although the measurement results were following the frequency behavior of the simulation results, a significant discrepancy between the measured and simulated frequency responses has been found. Section 3.6.1 show the analysis of the discrepancies between the model and measurements. The reason was due to the ground below the VD that was disregarded in the simulations. The agreement between computed and measured response of the VD with vertically placed resistors significantly improves when the ground is correctly modeled. However, the ground presence worsens the frequency behavior of the VD, which becomes undesirable for a RVD, even if acceptable with respect to the requirement of the standards for a normal voltage transducer. The analysis of the VD with vertically placed HV resistors has been published in the journal of “International review on electrical engineering”. In a next step, the general behavior of the 30 kV VD with horizontally placed HV resistors has been investigated since this configuration results to be more compact and should be less sensitive to proximity objects. In the previous configuration (the vertical one), the distances between high voltage nodes were large enough that small changes in the resistor placement or in the shield dimensions do not modify significantly the electric field. However, in this new configuration (the horizontal one), the electric field must be calculated by FEM for any modification of the parameters. Two different way of connections between HV resistors were modeled (section 3.7) with long and short connections. The comparison between the two configurations shows that the VD with shorter copper tube connection have a better behavior and so has been further investigated in the following. The RVD with horizontally placed resistors could give a good frequency behavior. However, the maximum electrical field strength could not be further lowered due to the nature of this configuration (section 3.7). In order to get an improved frequency behavior a zig-zag configuration has been introduced a topological variation of the horizontal configuration. The zig-zag VD lowers the maximum electrical field strength compared to the horizontal resistor VD (section 3.8). More than 50 cases of zig-zag VD with different parameters were simulated to reach the goal of the project design. A main part of the focus was on the shielding of the RVD in a way to control and manipulate the stray capacitances in order to make the VD error compliant with the design specification. The main drawback of this zig-zag RVD is the sensitivity towards the proximity effect. In section 3.8.8, a shielding with three different screen parts has been proposed. Such a shield could give a good frequency behavior with small proximity sensitivity. However, the model with three screens could not be realized at the moment as it requires special workshop tools, not available at the moment. A different approach has been achieved providing a reduction of the proximity effect (section 3.10). The zig-zag RVD has been fitted with an LV shield. The measurement results show an accuracy of ±980 ppm for the scale factor, up to 50 kHz, and less than 9 mrad for the phase error up to 32 kHz (2.1 mrad up to 10 kHz). This zig-zag RVD could be used in any laboratory environment after calibration for the specified perimeter. To further reduce the proximity sensitivity, HV capacitors have been added to the zig-zag RVD, which significantly reduces the effect of the stray parameters and the VD is much less affected by the proximity changes (stray capacitance changes). The result of zig-zag RCVD with LV connected shield shows a promising frequency behavior which could be considered as a reference voltage transducer. By connecting the LV shield to the ground one can obtain a further reduction of the proximity effect (section 3.10.3). The zig-zag reference RCVD with ground connected shield shows a maximum 244 ppm of scale factor uncertainty and less than 345 µrad of the phase error uncertainty from DC up to 10 kHz. The proximity effect investigation done in Sect 3.10.3 has highlighted that this divider (with ground-connected shield) exhibits very small proximity sensitivity. For example, if a grounded (or floating) object having size similar to the one of the divider approaches the VD up to 30 cm, the scale factor changes less than 91 ppm and the phase error is modified about 82 µrad.

The aim of this thesis is to propose a new method to detect High impedance Faults, which relies on measuring the phase currents on electrical transmission and distribution grids using a common time source for synchronization. The goal is to measure the residual currents both at the transformer side and at the load side of the network. The time synchronization allows synchronized real-time measurements of the two residual currents at the two ends of the grid. In normal operating conditions and in all load conditions (balanced or unbalanced), the residual currents will result almost equal at the two ends. When a High Impedance Fault occurs, the residual currents at the two ends will differ. The difference in magnitude of the residual currents are monitored in real time and used as a pick-up criteria.

Vzduchem izolované vysokonapěťové rozváděče jsou nedílnou součástí energetického distribučního řetězce a to jak v průmyslovém, tak ve veřejném sektoru. Hlavní funkcí rozváděče je ochrana pracovního personálu, rozpojování/odpojování a spínání, izolování, měření proudů a napětí, chránění a ovládání zatížení a komunikace dat do řídících systémů. V každé z výše zmíněných funkcí probíhal technologický vývoj v průběhu posledních 40 let. Dnešní rozváděče jsou spolehlivé a elektrickému oblouku odolné zařízení, zoptimalizované téměř k fyzikálním limitům dielektrických, elektromagnetických a termodynamických polí. Vakuové vypínače zajišťují stálou a spolehlivou vypínací funkci. Taktéž v oblasti chránění, řízení a komunikace došlo k mnoha technologickým proměnám. Od elektromechanických relé přes zařízení založená na tranzistorech, později na jednoúčelových mikroprocesorech, až po dnešní multifunkční vysoce výkonná mikroprocesorová inteligentní elektronická zařízení. Pouze oblast měření proudů a napětí setrvala z technologického hlediska posledních 40 let beze změny. K dominujícím měřícím technologiím dneška stále ještě patří indukčně založené transformátory proudu a napětí. Byly sice provedeny některé pokusy k obměně technologie měření jako takové, nicméně bez dosažení úspěchu. Tato dizertační práce je zaměřena na poskytnutí nového náhledu na alternativní technologii měření v elektrických sítích a ve vzduchem izolovaných vysokonapěťových rozváděčích, kterou lze využít jak pro měření proudu, tak i napětí. Tato práce vysvětluje, proč Rogowského cívky, odporové a kapacitní děliče jsou tou správnou volbou a měly by být použity ve vysokonapěťových rozváděčích a podrobně analyzuje přesnost měření a jejich příslušné meze. Dále tato práce popisuje, že pro nasazování nových měřících technologií musí být postupováno systematicky. Senzory připojené k inteligentním elektronickým přístrojům a schopností komunikace založené na IEC 61850 spolu s vysokorychlostní komunikační sběrnicí Ethernetu vytvoří systém, který zjednoduší a sjednotí konstrukci rozváděčů a umožní oddělit aspekty projektování měření od studie zkratových selektivit. V práci je také uveden příklad, jak tento nový systém může přinést změny a zjednodušení do oblastí projektování a řízení. V této práci jsou popsány výsledky několikaletého úsilí při stanovení nových měřících a digitalizovaných přístupů ve vysokonapěťových rozváděčích pod autorovým vedením. Toto úsilí také vedlo k uvedení nového produktu – UniGear Digital - konceptu od ABB. Závěrečná část práce demonstruje praktické nasazení všech výsledků v této práci při skutečných aplikacích.

This thesis concerns monitoring in Middle- and Low-Voltage distribution systems penetrated by distributed generation. Monitoring itself means measuring voltages and power flows and sending relevant data to the supervisory system. The first part of the thesis describes distribution systems with differences between individual voltage levels. The following chapter is focused on consequences of high share of renewable energy sources in distribution systems. Most of the problems are partially resolved by technical conditions for connection of the new power sources. However, difficulties with voltage regulation and uncontrolled power flows to higher voltage levels remain. These are the reasons for measuring voltages and currents in medium voltage networks. Second to last subhead of this chapter is dedicated to possible benefits of monitoring. The fourth part of the thesis deals with voltage and current sensors with their advantages and disadvantages. The best suitable devices are chosen in the end of the chapter. It is crucial to mention that sensors are only part of measuring system. Analog outputs from current or voltage transformers need to be converted to digital signal and further processed. After that required quantities are finally sent. Properties of these circuit cards are described in the sixth chapter. Following part aims to define a certain key that will determine the suitable locations for installation of the measurement. The final part of the thesis compares measured voltages and power flows from real 22 kV network with calculated values from computer program PAS DAISY Bizon.

Orientador: José Antonio Siqueira Dias
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
Made available in DSpace on 2018-08-26T13:53:46Z (GMT). No. of bitstreams: 1 Tercariol_WalterLuis_D.pdf: 1322557 bytes, checksum: 4f45518a1a62907cd9a61afa627408c3 (MD5) Previous issue date: 2014
Resumo: Este trabalho visa compilar três contribuições na melhoria dos projetos de reguladores de tensão com unidades de bombeamento de carga embutidos (células elevadoras de tensão Dickson - BC). A primeira aborda uma técnica inovadora de arranque na partida deste módulo elevador quando habilitado. Este projeto se refere à aceleração da inicialização do modulo BC, tendo como objetivo a diminuição do intervalo de tempo da rampa ascendente da tensão de saída Vo até atingir o nível alvo de regulação. A técnica consiste em gerenciar o aumento da freqüência do relógio de bombeamento entregue as unidades de bombeamento durante a fase de subida, quando a regulação estiver estabelecida o sistema se regenera voltando ao estado original de freqüência de bombeamento natural. Uma segunda proposta inovadora de projeto é referente à homogeneização e redução da aleatoriedade da ondulação da tensão de saída Vo, referente ao regulador com o modulo BC embutido, baseado em comparadores com trava, com proposta de redução do erro de comparação devido ao efeito aleatório durante o estagio de comparação comumente encontrado neste tipo de abordagem, a técnica consiste em suprimir o acoplamento capacitivo nocivo durante a fase de isolamento elétrico no processo de comparação mantendo o espelho de corrente do comparador na região de saturação. Esta técnica visa proporcionar uma redução significativa da capacitância de desacoplamento utilizada para filtragem da tensão Vo. Uma terceira e última contribuição é referente a uma inovadora técnica de medição indireta da tensão de saída Vo do regulador com módulo BC baseada em uma medida simples e precisa dos pares tensão da porta e fonte (VPS) e corrente elétrica do dreno (Idreno) de um dispositivo NMOS de alta tensão adicionado de modo que duas tensões conhecidas (preestabelecidas) são aplicadas na porta do dispositivo e as respectivas correntes de dreno são mensuradas e uma terceira desconhecida (oriunda do regulador elevador BC) desconhecida pode ser extrapolada de forma simples. Esta técnica visa ser útil para medição de reguladores de baixa potencia pois o carregamento do regulador (Vo) é quase nulo.Todas as inovações e melhorias propostas foram analisadas em veículos de teste (silício) e com as provas de conceito, feitas em simulações elétricas
Abstract: This work aims to compile contributions in improving designs based on voltage regulators with voltage elevator with built-in charge pump CP. The first deals with an innovative technique rump-up this module when enabled. This project refers to the acceleration of startup the CP module, aiming at the reduction of the period of stabilization of the ramp output voltage Vo to the level of regulation target. The technique is to manage increasing the frequency of pumping clock during the phase of rump up and when the setting established the system regenerates back to the original state pumping frequency. A second innovative project proposal was made on the homogenization and reduction of the ripple of the output voltage Vo, referring to the regulator with the |CP module, based on latch comparators , alignment error reduction proposal because of the random effect during the stage comparison commonly found in this type of approach, the technique is to remove the harmful capacitive coupling during electrical isolation phase on the comparison keeping the comparator current mirror in saturation region. This technique aims to provide a significant reduction in the decoupling capacitance used for filtering the voltage Vo. A third and final contribution is related to an innovative technique of indirect measurement of the output voltage Vo of the regulator module CP, based on a simple and accurate measure of the gate voltage and couples the drain electric current of a high voltage NMOS device
Doutorado
Eletrônica, Microeletrônica e Optoeletrônica
Doutor em Engenharia Elétrica

El món de les comunicacions per la xarxa elèctrica (CXE) pot ser dividit en tres grans tipus: CXE en baix voltatge (CXE-BV), en mig voltatge (CXE-MV) i en alt voltatge (CXE-AV). En aquests últims anys, les CXE-BV han atret una gran expectació, ja que les seves capacitats han fet d'aquesta tecnologia una bona opció com alternativa pel bucle local d'accés i pel desplegament de xarxes d'àrea local, focalitzades aquestes últimes en l'entorn domèstic. A més, les CXE-BV inclouen un conjunt d'aplicacions de baixa velocitat orientades a l'operador, com la lectura automàtica de comptadors (LAC), distribució de càrrega, facturació dinàmica, etc. Per altra banda, les CXE-MV i CXE-AV, històricament lligades a tasques de telecontrol i teleprotecció, s'estan començant a considerar com un canal de comunicacions eficient i fiable. El desenvolupament de sistemes digitals i els esforços d'estandardització estan fent d'aquests canals un medi atractiu per a que els operadors elèctrics ofereixin serveis de comunicacions, ja que no necessiten invertir en infraestructura perquè la xarxa elèctrica ja està desplegada.
En aquesta Tesi s'introduiran i es comentaran les particularitats de les tres xarxes elèctriques, després, es mostraran al lector les solucions tecnològiques existents pels canals de BV basats en la norma Europea CENELEC així com pels canals d'AV, mostrant que els sistemes actuals de LAC ofereixen una diversitat freqüencial molt baixa i que els mòdems CXE-AV estan ancorats en estendards antiquats.
Aquest treball es mou per les tres topologies de la xarxa, particularment, en aplicacions orientades a la banda CENELEC, en mesura i modelat de canal, i en mesura i disseny del nivell físic per sistemes CXE-BV, CXE-MV i CXE-AV respectivament. Els sistemes actuals que exploten la banda CENELEC ofereixen mecanismes d'explotació de la diversitat freqüencial del canal molt limitats o nuls, donant lloc a una baixa robustesa en front a interferències i soroll de fons acolorit. Aquest treball proposa un esquema de modulació multiportadora que, mantenint una complexitat baixa, ofereix unes altes prestacions permetent un bon nivell d'explotació de la selectivitat freqüencial. Per al que a CXE-MV respecta, aquesta Tesi desenvolupa un model de canal determinístic-estadístic pels anells urbans de distribució de potència i, finalment, en sistemes CXE-AV, aquest treball proposa, basat en mesures de canal i proves de camp, un nivell físic de banda ampla capaç de incrementar la velocitat de comunicació mentre manté una baixa densitat espectral de potència limitant així la interferència a altres sistemes.
PARAULES CLAU: Power line communications (PLC), low voltage (LV), medium voltage (MV), high voltage (HV), automatic meter reading (AMR), orthogonal frequency division multiplexing (OFDM), multicarrier spread spectrum (MC-SS), communication system design, channel measurements, channel modeling, scattering parameters.
El mundo de las comunicaciones por la red eléctrica (CRE) puede ser dividido en tres grandes tipos: CRE en bajo voltaje (CRE-BV), en medio voltaje (CRE-MV) y en alto voltaje (CRE-AV). En estos últimos años, las CRE-BV han atraído una gran expectación, ya que sus capacidades han hecho de esta tecnología una buena opción como alternativa para el bucle local de acceso y para el despliegue de redes de área local, focalizadas estas últimas en el entorno doméstico. Además, las CRE-BV incluyen un conjunto de aplicaciones de baja velocidad orientadas al operador como la lectura automática de contadores (LAC), distribución de carga, facturación dinámica, etc. Por otro lado, las CRE-MV y CRE-AV, históricamente ligadas a tareas de telecontrol y teleprotección, se están empezando a considerar como un canal de comunicaciones eficiente y fiable. El desarrollo de sistemas digitales y los esfuerzos de estandarización están haciendo de estos canales un medio atractivo para que los operadores eléctricos ofrezcan servicios de comunicaciones, ya que no necesitan invertir en infraestructura porque la red eléctrica ya está desplegada.
En esta Tesis se introducirán y se comentarán las particularidades de las tres redes eléctricas, luego, se mostrarán al lector las soluciones tecnológicas existentes para los canales de BV basados en la norma Europea CENELEC así como para los canales de AV, mostrando que los sistemas actuales de LAC ofrecen una diversidad frecuencial muy baja y que los módems CRE-AV están anclados en estándares anticuados.
Este trabajo se mueve por las tres topologías de red, particularmente, en aplicaciones orientadas a la banda CENELEC, en medida y modelado de canal, y en medida y diseño del nivel físico para sistemas CRE-BV, CRE-MV y CRE-AV respectivamente. Los sistemas actuales que explotan la banda CENELEC ofrecen mecanismos de explotación de la diversidad frecuencial del canal muy limitados o nulos, dando lugar a una escasa robustez frente a interferencias y ruido de fondo coloreado. Este trabajo propone un esquema de modulación multiportadora que, manteniendo una complejidad baja, ofrece unas altas prestaciones permitiendo un buen nivel de explotación de la selectividad frecuencial. Por lo que a CRE-MV respecta, esta Tesis desarrolla un modelo de canal determinístico-estadístico para los anillos urbanos de distribución de potencia y, finalmente, en sistemas de CRE-AV, este trabajo propone, basado en medidas de canal y pruebas de campo, un nivel físico de banda ancha capaz de incrementar la velocidad de comunicación mientras mantiene una baja densidad espectral de potencia limitando así la interferencia a otros sistemas.
PALABRAS CLAVE: Power line communications (PLC), low voltage (LV), medium voltage (MV), high voltage (HV), automatic meter reading (AMR), orthogonal frequency division multiplexing (OFDM), multicarrier spread spectrum (MC-SS), communication system design, channel measurements, channel modeling, scattering parameters.
The world of Power line communications (PLC) can be divided into three main types: low voltage PLC (LV-PLC), medium voltage PLC (MV-PLC) and high voltage PLC (HV-PLC). These last years, LV-PLC has attracted a great expectation since its wideband capabilities has made this technology a suitable choice for last-mile access and in-home communications. Moreover, LV-PLC also includes a utility oriented low frequency and low speed applications, such as automatic meter reading (AMR), load distribution, dynamic billing and so on. On the other hand, MV-PLC and HV-PLC, historically oriented to teleprotection and telecontrol tasks, are being considered as a reliable communication channel. The development of digital equipment and the standardization efforts are making those channels an attractive medium for electrical utilities telecommunications services, since the network, as well as in LV-PLC, is already deployed.
In this PhD dissertation, the three different PLC topologies are reviewed and the different communications techniques in such channels exposed. Then, a deep technological review of existing AMR solutions for the European CENELEC band, as well as HV-PLC systems is given, showing that existing AMR systems deliver low frequency diversity and HV-PLC systems are anchored in old fashioned standards.
This work walks around the three topologies, specifically, CENELEC band utility oriented applications, channel measurement and modeling and channel measurement and physical layer design, regarding LV-PLC, MV-PLC and HV-PLC respectively. Existing CENELEC compliant systems deliver low or none frequency diversity mechanisms, yielding in a low robustness against colored noise and interference. This work propose a multicarrier based physical layer approach that, while keeping the complexity low, delivers high performance allowing a great level of frequency diversity. Focusing on MV-PLC, a hybrid deterministic-statistical channel model for urban underground rings is developed and, finally, in HV-PLC systems, this work proposes, based on measurements and field tests, a wideband physical layer in order to increase data rate while keeping low both the power spectral density and possible interference to other systems.
KEYWORDS: Power line communications (PLC), low voltage (LV), medium voltage (MV), high voltage (HV), automatic meter reading (AMR), orthogonal frequency division multiplexing (OFDM), multicarrier spread spectrum (MC-SS), communication system design, channel measurements, channel modeling, scattering parameters.

O trabalho tem por objetivo o estudo e o desenvolvimento de interferômetros recuperadores com baixa tensão de meia onda utilizando moduladores eletro-ópticos para serem aplicados em sistemas Interferométricos de luz branca. Ele dá continuidade às pesquisas do autor em seu mestrado, em que foi desenvolvido e testado um sistema de sensoriamento eletro-óptico capaz de medir diretamente tensões de até 69,4 kVRMS. Desta forma aperfeiçoa-se o sistema de processamento de sinais ópticos desenvolvendo um novo interferômetro recuperador, baseado em óptica integrada. Para o desenvolvimento do tema proposto, inicialmente foi feito uma revisão da literatura/bibliografia, baseada em livros, artigos e teses, visando identificar o \"estado da arte\" relacionado aos moduladores eletro-ópticos para definir o tipo de modulador mais adequado à aplicação em vista. O estudo resultou na escolha de um componente em óptica integrada que foi aplicado numa configuração inédita em um protótipo de transformador de potencial óptico para medição de elevados níveis de tensão elétrica. As características de desempenho deste protótipo foram comparadas com as do protótipo previamente construído. Como resultado deste trabalho, amplia-se o conhecimento e fixa-se em âmbito nacional o domínio sobre as técnicas de construção de interferômetros recuperadores baseados em óptica integrada aplicáveis à recuperação de sinais ópticos em sistemas interferométricos para medição de altas tensões.
This work has as objective the study and development of low half-wave voltage recovery interferometers using electro-optical modulators to be applied to white light interferometric systems. This work is a continuation in the research carried out by the author to obtain his master degree, in which it was developed and tested an electro- optic sensing system capable to measure direct voltage to 69.4 kVrms. In the present work the optical signals processing system is improved by developing a new recovery interferometer based on integrated optics. To develop the proposed subject, initially a review of the literature, based on books, articles and thesis, has been done aiming to identify the State of the Art related to electro-optic modulators and helping to define the most suitable type of modulator for the desired application. The study resulted in the selection of an integrated optical device arranged in an unpublished configuration that was applied to a prototype of optical voltage transformer, intended to measure high voltage levels. The performance of this prototype was compared with a previous version. The results of this work increase the knowledge of the construction techniques of recovery interferometers based on integrated optic devices applicable to the recovering of optical signals in interferometric systems for high voltage measurement.

Student Number : 9811492X - MSc dissertation - School of Electrical and Information Engineering - Faculty of Engineering and the Built Environment
This dissertation discusses the development of an ATP model of a network to aid measurement techniques in a harmonic evaluation. A theoretical back- ground discussion of various pieces of equipment and their signi#12;cance to har- monics is included. National Electricity Regulator (NRS 048) standards are discussed with refer- ence to performing a basic investigation and short comings. A test study was performed on the Brandspruit Mine in Secunda. ATP models are developed for equipment relevant to the test case, these in- clude AC{AC converters, AC{DC converters, three phase transformers and cables. Finally the measured test case is compared to simulation results and conclusions drawn.

Sensor performance characteristics are generally divided into at least two categories: static and dynamic. Additional categories sometimes used include drift and exposure errors. The performance of sensors in conditions where the measurand is constant or very slowly changing can be characterized by static parameters. Dynamic performance modeling requires the use of differential equations to account for the relation between sensor input and output when the input is rapidly varying. Static characteristics due to friction or other nonlinear effects would vastly complicate the differential equations so, even when the input is not steady, static and dynamic characteristics are considered separately. Static characteristics are determined by carefully excluding dynamic effects. Dynamic characteristics are assessed by assuming that all static effects have been excluded or compensated. Many of these terms have been encountered in chaps. 1 and 2, although without formal definitions. Analog signal. A signal whose information content is continuously proportional to the measurand. If an electrical temperature sensor has a voltage output, that voltage signal fluctuates with the sensor temperature. Voltage output would be continuously proportional to the measurand (temperature) and is analogous to it, hence we refer to the sensor output as an analog signal. Data display. Any mechanism for displaying data to the user. The stem of a mercury-in-glass thermometer with attached scale is a data display. Data storage. A memory element or mechanism for holding data and later recovering them such as a disk or magnetic tape. Again, this could be as simple as a piece of paper. Data transmission. The process of sending a signal from one place to another. The data transmission medium could be a piece of paper, a magnetic tape, radio or light waves, or telephone wires. Digital signal. A signal whose information content varies in discrete steps. The step size can be made arbitrarily small such that a plot of a digitized signal could also resemble the analog signal. However, the granularity of a digital signal will be revealed if it is examined in sufficient detail.

Ultrasound has many uses in areas of medicine associated with anaesthesia. It is used for imaging, visualisation of needle and catheter positioning, therapy and, together with the Doppler effect, for measurement of flow velocity. Real-time information can be obtained with ease, and with the low energies used, diagnostic equipment exposures are not thought to be a safety issue, either for the operator or the patient. Ultrasound is a form of mechanical energy that consists of high frequency vibrations at frequencies above human hearing range (> 20 kHz) and up to frequencies in the tens of MHz range. The frequencies used are dependent on issues such as the penetration and resolution required. It is thought that low intensity ultrasound passes through living tissue without altering tissue function. Higher energy can produce heating and cavitation, both of which can alter cell function. Ultrasound is generated by electrically inducing a deformation in a piezoelectric crystal, which compresses and decompresses the medium to which it is coupled at a rate equal to the frequency of the driving voltage. The pressure changes travel through the medium in a longitudinal direction and the distance between the points of maximum pressure, or compression, is known as the wavelength. Figure 10.2 shows the relationship between the period of the wave and the wavelength. The length of this distance is dependent on the elasticity (compressibility) and the density of the medium, and the delay between the movement of adjacent particles in the medium. As shown in the figure, the wavelength (λ) and the transmission frequency (f) are related to the propagation velocity c by c = f λ. The magnitude of the wave is the difference between the maximum and minimum pressure values. The wave propagates by movement of particles: it cannot travel in a vacuum and it does not ionise the medium through which it travels. The propagation of an ultrasound wave is not constant throughout the body. Various parts allow the passage of the wave at different velocities. Also the wave is attenuated differently by the various tissue types. For example, in soft tissues the ultrasound wave has a velocity of between 1460 and 1630 m s−1 whereas in bone it is 2700–4100 m s−1.

This chapter presents a new method for loss of excitation (LOE) faults detection in hydro-generators using adaptive neuro fuzzy inference system (ANFIS). The investigations were done under a complete loss of excitation conditions, and a partial loss of excitation conditions in different generator loading conditions. In this chapter, four different techniques are discussed according to the type of inputs to the proposed ANFIS unit, the generator terminal impedance measurements (R and X) and the generator terminal voltage and phase current (Vtrms and Ia), the positive sequence components of the generator terminal voltage magnitude, phase current magnitude and angle (│V+ve│, │I+ve│ and ∟I+ve) in addition to the stator current 3rd harmonics components (magnitudes and angles). The proposed techniques' results are compared with each other and are compared with the conventional distance relay response in addition to other techniques. The promising obtained results show that the proposed technique is efficient.