Performance Evaluation of Powerline Technology on Low Voltage Distribution Networks

Powerline technology (PLT) employs the electrical distribution network to transmit data in addition to supplying power. PLT is currently employed to provide data networking in many domestic environments, and is expected to play a major part in the development of the forthcoming Smart Grid. Given that the electrical distribution network was not designed with data transmission in mind, electromagnetic radiation from the network can give rise to interference. Regulators and researchers have considered the impact of such widespread radiation, and investigations of the various aspects of powerline have been conducted over the last decade. Despite this prolonged period, however, there remains a lack of agreement on the typical performance of such networks or the implications for regulation policy. An accurate model of the radio frequency (RF) properties of the typical electrical distribution network would be extremely valuable in developing standards and informing policy. The aim of this thesis is to provide a cohesive approach to determining the RF characteristics of a typical domestic property and applying such parameters to model the performance of PLT. The thesis reviews the recent development of broadband PLT, the progress made by the more prominent regulators, and the trials undertaken to define the key parameters affecting propagation. A detailed experimental programme carried out both in the laboratory and at typical sites is described. An empirical model of the RF performance of a UK domestic low voltage distribution network (LVDN) is developed from analysis of the experimental results. It is shown via this analysis that discrete measurements of the conducted and radiated parameters can be related and that the RF performance of the LVDN can be described by Conversion and Radiated Loss. The radiated field is shown to comprise the combined common mode current to the LVDN and common bonding network (CBN). The thesis concludes with consideration of the future development of powerline technology, particularly in support of the Smart Grid development

Interference analysis of high frequency power line communications

Abstract. In power line communications, the existing in-house or in-office power distribution network can be used as a communications channel. Current broadband power line communication systems in the market deploy frequency range up to 86 MHz with transmission speeds up to 1 Gb/s. To increase the capacity even further, an extension of the frequency range above 100 MHz has been proposed in the published literature. This thesis presents an empirical study of radiated interference of high frequency broadband power line communications. Utilization of high frequencies for power line communications will cause unwanted radio interference which needs to be treated with caution. The preliminary results obtained in this work show how the components and structures of a power grid segment will contribute to the overall interference radiation when frequencies above 100 MHz are used for power line communication. The results indicate that the peak levels of radiated interference from a typical cabling in in-house or in-office power line networks reach their maximum on frequencies near 300 MHz and remain on a relatively same level on above. The peak levels are approximately 13 dB above the EN 55022 limit in the 230–1000 MHz frequency range with an injected power spectral density of -80 dBm/Hz. The results will provide valuable information when designing and making more comprehensive measurement campaigns for deciding on the national transmission levels for power line communications in UHF and higher frequencies.Korkeataajuisen sähköverkkotiedonsiirron aiheuttama säteily. Tiivistelmä. Sähköverkkotiedonsiirrossa hyödynnetään olemassa olevaa sähköverkkoa tiedonsiirtokanavana. Tällä hetkellä käytössä olevat sähköverkkotiedonsiirron standardit käyttävät taajuuksia 86 MHz:iin asti. Saavutettavat tiedonsiirtonopeudet yltävät 1 Gb/s asti. Kapasiteetin kasvattamiseksi on julkaistussa kirjallisuudessa esitetty taajuusalueen laajentamista yli 100 MHz:n taajuuksille. Tässä diplomityössä esitetään empiirinen tutkimus korkeataajuisen sähköverkkotiedonsiirron aiheuttamasta säteilystä. Korkeiden taajuuksien käyttö sähköverkkotiedonsiirrossa aiheuttaa haitallista säteilyä, joka täytyy ottaa huomioon ennen kuin taajuusaluetta voidaan laajentaa. Työssä saavutetut tulokset osoittavat kuinka sähköverkon eri komponentit vaikuttavat kokonaissäteilyyn kun yli 100 MHz:n taajuuksia käytetään sähköverkkotiedonsiirrossa. Tulokset osoittavat että tyypillisen talon tai toimistorakennuksen sähköverkossa siirretyn korkeataajuisien signaalin vuotama säteily saavuttaa maksimitasonsa 300 MHz:n taajuuteen mennessä ja ei kasva sitä korkeammilla taajuuksilla. Säteilyn maksimitasot ovat noin 13 dB EN55022 standardin rajojen yläpuolella taajuuksilla 230–1000 MHz kun sähköverkkoon syötetyn signaalin tehollinen tehotiheys on -80 dBm/Hz. Tuloksia voidaan käyttää hyödyksi laajempia mittauskampanjoita suoritettaessa kansallisten tehorajoitusten päättämiseksi kun UHF ja sitä korkeampia taajuuksia käytetään sähköverkkotiedonsiirrossa

The radio spectrum requirements of broadband power line telecommunications systems.

There is concern among short wave (HF) radio users that broadband Power Line telecommunications (PLT) systems could cause serious interference to their services. The purpose of my research was to identify the factors that determine the performance of broadband PLT systems and to investigate how to maximise system performance while minimising the effect of PLT on HF radio systems. The study concentrates on the requirements for Access Band systems used to provide local loop service operating on 230/400V three-phase Low Voltage mains distribution networks. The basis of the study is a comprehensive set of measurements made on Low Voltage mains distribution networks in the UK, mainland Europe and Australia. The new approach to PLT band planning taken in this thesis uses Claude Shannon's information theory to predict the data capacity of arbitrary 3MHz sub bands. The results of the measurement programme are used to determine an optimum frequency band plan for PLT systems, taking account of the needs of the systems and the protection of other users of the HF spectrum. An example of how the proposed band plan can be used on a typical LV distribution network is included. The use of the mathematical models with the results of the attenuation, noise and emission measurements show that it is possible to improve on both the frequency band plans proposed in current PLT standards and the nonstandard frequency usage of many PLT trial systems. This will facilitate the achievement of competitive performance without causing undue radio interference, thus potentially making broadband PLT more acceptable to the HF radio community. The choice of modulation and coding systems required to deliver the predicted performance in the presence of transient interference is also discussed

Investigation into the impedance and communication requirements for the low voltage distribution line in the high frequency spectrum

Power Line Communications is long established for low data rate applications over high- voltage power lines. It is now charting new territory in high speed data transmission to the high frequency band of IMHz and upwards over the low-voltage segment below the distribution transformers.' Since the power line is designed for transmission of power instead of signal transmitting originally; it has many shortages when used as a signal communication channel. The heterogeneous structure of the power line network with numerous branches and impedance mismatcheS causing reflections and attenuations during signal transmission, and thus communication signal cannot be sent out or received completely. From this point of view, the power line impedance is a very important parameter in the design of power line communication (PLC) modem architecture, which is subject to legislations that limit the signals in the line. Variations on the impedance of the power line affect the communications channel performance. For the optimum modem design, power line impedance must be known. Power line impedance changes with time, carrier frequency, load variations, architectures and locations of the lines in city, urban, rural & industrial environment. The objective of this study is to determine the impedance of power distribution network in a frequency range from IMHz to 30MHz. This is in line with international standard bodies including CENELEC, IEC, ITV and ETSI, which stipulates that for propagation characteristics of power line and EMC regulations, data transmission rate are evolving and . are being extended all the time to data rate up to 100 Mbps. This thesis covers impedance measurements carried out in college buildings in Somerset, UK together with some residential houses in Somerset and London. The college buildings have both three-phase and single-phase architectures with various laboratories where loads are randomly switched on and off. An impedance analyser is used to carry out the measurements which performs a scan through a programmable frequency limits and acquires impedance parameters in the frequency domain Measurements were monitored using Microsoft Remote Desk Top client application Series of experimental measurements were carried out in the Bridgwater College and residential houses in Bridgwater and also in London. The first part of the thesis offers detailed introduction to the topics of electricity supply networks, power line communications, modulation techniques and electromagnetic compatibility, noise and transmission line characteristics. From the experimental results, presented in graphical format, a number of conclusions can be drawn. A wide range of impedances are observed for single phase measurements, within the range of 3 - 584 Ω for large buildings and residential houses. For three phase measurements impedances varied from 21 - 340 Ω. The thesis concludes with a suggestion of how these measurements may be used in PLC modem design. Dynamic output-impedance PLC modems may be designed using a real-time impedance detector of the power line and the adjustable output impedance-power amplifier. Therefore, modem output impedance may be matched to the real time line impedance

Powerline Kommunikation: Wesentliche Technologien um PLC in CE-Geräte zu integrieren

In-house PLT (Powerline Telecommunication) enables new and highly convenient networking functions without the need for additional cables on mains-powered devices. Since wireless networks are not able to reach sufficient throughput between different rooms or even floors, PLC is considered to be the ideal backbone home network medium, providing complementary and seamless interaction with wireless networks. The need to communicate information is not new. The historical overview of this thesis compares the development of PLT to radio broadcast technologies. The consumer expects technologies to operate without interferences. Today, there are coexistence problems between these two technologies. Why does this happens, and how the problems can be resolved are the main issues of this thesis. Initial calculations of the channel capacity provide encouraging results for using the mains cabling as a communication medium. Chapter 3 forecasts how PLT modems could develop in the future. The usage of frequencies above 30 MHz will increase the throughput rate. Next, the utilization of the 3rd wire (the protective earth) for communication enhances the coverage and the reliability of powerline transmissions. The reception of common mode signals and the usage of MIMO technologies enable 8 transmission paths between one pair of outlets, which improves the performance of the bad, strongly attenuated channels. Today, the main challenge for the mass deployment of PLT is the lack of harmonized international standards on interoperability and electromagnetic interference. The absence of a standard results in the undesirable situation of PLT modems interfering with technologies from different vendors and also with radio applications. Solutions for solving these problems are given in chapter 4 and chapter 5. The approach of ‘Smart Notching’ - monitoring the existence of receivable radio broadcast stations at the time and location where a PLT modem is operating, received wide resonance in the PLT and radio broadcast communities. ‘Smart Notching’, also called ‘Dynamic Notching’ or ‘Adaptive Notching’ is considered to be the key factor in solving the endless discussions about the interferences to HF radio broadcast. Details on the creation of ETSI TS 102 578 and the implementation of a demonstrator system is documented in chapter 5. Field tests conducted together with the EBU verified the efficiency of the concept. The jointly executed tests by representatives from the radio broadcast and the PLT communities became a historical event which brought the two technologies, radio receivers and PLT modems, back into one house. Finally, a vision of the future coordination of EMC and conclusions are presented.Heutige Modems zur Powerline Telekommunikation (PLT) können im Betrieb den Empfang von Kurzwellen-Rundfunk beeinträchtigen, wenn Modem und Rundfunk-Empfänger in unmittelbarer Nachbarschaft betrieben werden. Eine neue Generation von PLT Modems, in denen das Konzept von 'Smart Notching' - dem intelligenten Einfügen von Lücken in das Kommunikationsspektrum - implementiert ist, zeigt keine Interferenzen mit dem Empfang von Rundfunkdiensten. Das Rauschen auf der Niederspannungsinstallation enthält neben sonstigen Signalen - durch andere Geräte hervorgerufen - aufgrund der Antennenwirkung Information über Rundfunksender. Beim ‚Smart Notching’ erkennen PLT Modems am Betriebsort die Existenz von Rundfunksignalen, indem sie das Signalspektrum auf der Netzleitung messen. Die Echtzeit- Bewertung der aktuellen Situation am Betriebsort ermöglicht eine Adaption des PLT Systems. Damit wird die Elektromagnetische Verträglichkeit nicht a priori (zum Herstellungs-Zeitpunkt) durch Schirmung oder eine globale Reduktion des Sendepegels, sondern durch Design des Verfahrens (welches während des Betriebs angewendet wird) hergestellt. Diese Doktorarbeit beschreibt nach einem kurzen Überblick zur Historie des Rundfunks und der Datenübertragung über das Energieverteilnetz Messungen zur Ermittlung der theoretischen Kanalkapazität. Anschließend wird ein Ausblick gegeben, wohin sich zukünftige PLT Modems entwickeln werden. Dies sind vor allem der Frequenzbereich oberhalb von 30 MHz sowie die Nutzung der dritten Kupferader in den Netzleitungen: der Schutzerde. Die Verwendung von MIMO-Algorithmen (aus der kabellosen Funkübertragung (z.B. WiFi) bereits bekannt) verbessert vor allem die Wahrscheinlichkeit, eine hohe Datenrate im Gebäude sicher zu verteilen. Sorge bereitet bei PLT ebenfalls die Koexistenz mit weiteren PLT-Systemen, sowie zu xDSL. Hierfür wird ein Vorschlag gemacht, um die Interferenzen zu nicht kompatiblen PLToder DSL-Systemen zu vermeiden, ohne dass die Systeme sich gegenseitig gezielt Informationen zusenden. Das bereits oben erwähnte Konzept des ‚Smart Notching’ wird detailliert erläutert und die Implementierung eines Demonstrators auf FPGA-Basis dokumentiert. Abschließend wird noch beschrieben, wie ‚Smart Notching’ gemeinsam mit der EBU getestet wurde und wie es seinen Weg in die Welt der Standardisierung gefunden hat. Der Veröffentlichung des Standards ETSI TS 102 578 wurde im Juli 2008 einstimmig von ETSI PLT zugestimmt

Caractérisation et modélisation du canal et du bruit pour les réseaux CPL MIMO domestiques

Power Line Communication (PLC) technology provides the omnipresence of high speed data services without requiring the installation of new infrastructure. The existing household electrical wiring which is used to deliver the electrical energy to the house is utilized by the PLC technology as a transmission channel. The data rates of several hundreds of Mbps are realized by the PLC technology. In most developed countries the cable used for household electrical wiring consists of three wires: Phase (P), Neutral (N) and Protective Earth (PE). The existing PLC systems use the P-N port to transmit and receive the signals. It is a typical single input single output (SISO) transmission. The inclusion of the PE wire at transmit and receive outlets leads to the availability of multiple transmit/receive ports which in turn leads to the realization of a MIMO communication channel. The principle objective of this thesis is to study and explore the inhome PLC channels in the MIMO context. The main objectives of the thesis are categorized as the following: ¿ Development of a channel sounding protocol to perform extensive channel and noise measurements on the inhome PLC networks, with the objective of generating a rich and realistic database. Evaluation of the MIMO PLC channel capacity by utilizing the database obtained from the measurements. ¿ Characterization and modeling of the inhome MIMO PLC channel through a set of parameter by utilizing the measured channel data. Evaluation of the performance of the channel model by comparing the simulated channels parameters with the measured ones. ¿ Characterization and modeling of the MIMO power line noise through various parameters by utilizing the measured noise data. Evaluation of the performance of the noise model by comparing the simulated noise characteristics with the measured noise.La technologie Courants Porteurs en Ligne (CPL) répond aux besoins de couverture des services à haut débit sans nécessiter l'installation de nouvelle infrastructure. Dans la plupart des pays développés, le câble utilisé pour construire le réseau domestique d'énergie est constitué de trois fils : le fil de Phase (P), le fil de Neutre (N) et le fil de Terre (en anglais, Protective Earth, PE). Les systèmes CPL actuels utilisent les fils P et N (que l'on notera port P-N) pour émettre et recevoir des signaux de manière différentielle. Typiquement, il s'agit d'un mode transmission utilisant un capteur à l'émission et un capteur à la réception, ce que l'on nomme généralement transmission Single Input Single Output (SISO). Dans le domaine de la communication sans fil, les techniques Multiple Input Multiple Output (MIMO) sont largement employées pour augmenter la capacité du canal. Elles consistent à utiliser plusieurs antennes à l'émission et plusieurs antennes à la réception et bénéficier ainsi de la diversité du canal. Dans le contexte CPL, la présence du fil PE dans les prises électriques de transmission et de réception permet d'envisager la possibilité d'utiliser plusieurs ports d'émission et de réception, ce qui constitue un canal de communication MIMO. Des mesures et des simulations réalisées pour les canaux de transmission CPL ont montré une nette augmentation de la capacité du canal en utilisant les techniques MIMO par rapport aux systèmes traditionnels SISO. L'objectif principal de cette thèse est l'étude et l'exploration des canaux CPL domestiques dans le contexte MIMO. Il s'agit d'une étude détaillée des technologies CPL existantes et d'une investigation des caractéristiques des canaux CPL MIMO. Les objectifs principaux de la thèse sont : Le développement d'un protocole de sondage afin de réaliser des mesures intensives du canal de transmission et du bruit électromagnétique sur les réseaux CPL domestiques. L'objectif est de générer une base de données riche et réaliste. La base de données obtenue par les mesures permettra d'évaluer la capacité du canal CPL MIMO. La caractérisation et la modélisation du canal de transmission CPL MIMO domestique via un ensemble de paramètres, en utilisant les mesures de canal obtenues par la campagne de mesure. La performance du modèle de canal sera évaluée par la comparaison entre les canaux simulés et les canaux mesurés. La caractérisation et la modélisation du bruit électromagnétique CPL MIMO via plusieurs paramètres, en utilisant les mesures de bruit obtenues par la campagne de mesure. La performance du modèle de bruit sera évaluée par la comparaison entre le bruit simulé et le bruit mesuré

Transmission haut-débit sur les réseaux d'énergie: principes physiques et compatibilité électromagnétique

Power Line Communications consist of transmitting data by reusing the existing powerline as a propagation medium. Powerline networks represent a challenging environment for broadband communications, since they have not been designed for the transmission of high frequency signals. This Habilitation degree thesis presents our research on transmission physics and electromagnetic compatibility for in-home powerline networks. This research has been conducted since 2007 in the framework of a collaboration between Orange Labs and Telecom Bretagne, involving my supervision of three Ph.D. theses defended in 2012, 2013 and 2015, as the principal advisor.La technologie Courant Porteur en Ligne consiste à transmettre des données en réutilisant le réseau électrique classique en tant que support de propagation. Les réseaux d'énergie sont des environnements difficiles pour les communications à haut débit, car ils n'ont pas été conçus pour la transmission d'un signal à haute fréquence. Ce mémoire d'Habilitation à Diriger des Recherches présente mes travaux concernant la physique de la transmission et les aspects de Compatibilité Electro-Magnétique (CEM) pour le réseau électrique domestique. Ils ont été réalisés à partir de 2007 dans le cadre d'une collaboration entre Orange Labs et Telecom Bretagne, notamment à travers trois thèses soutenues en 2012, 2013 et 2015. Après une introduction générale à la technologie CPL, le manuscrit décrit l'environnement de propagation dans les réseaux d'énergie en termes de canal et de bruit électromagnétique. Les principes de la modélisation du canal CPL sont illustrés à partir de la problématique d'identification des trajets de propagation. L'une des principales évolutions du domaine concerne l'application de la technologie Multiple Input Multiple Output (MIMO) aux communications sur réseaux d'énergie. Nos études expérimentales ont démontré que l'adaptation de cette technique issue du domaine de la radio permet un doublement de la capacité de transmission. Nous présentons les campagnes de mesure réalisées au sein d'Orange Labs et du groupe Specialist Task Force 410 de l'ETSI. A partir de ces données, des modèles statistiques de canal de propagation MIMO et de bruit multi-capteurs ont été élaborés. En termes d'émission électromagnétique, la bande utilisée par les systèmes CPL est déjà occupée par d'autres services (radio amateur, radiodiffusion en ondes courtes). Nous décrivons les contraintes CEM des systèmes CPL et abordons les techniques de CEM cognitive, consistant à optimiser les ressources spectrales en tenant compte de la connaissance de l'environnement du système. En particulier, la technique de retournement temporel est étudiée pour la mitigation du rayonnement involontaire et sa performance est étudiée de manière expérimentale. Enfin, le manuscrit présente la problématique de l'efficacité énergétique des systèmes CPL. Nous présentons les mesures expérimentales réalisées afin de modéliser la consommation de modems classiques et MIMO. D'autre part, la configuration de communication en relais a été étudiée, afin d'évaluer le gain de ce mode de transmission en termes de consommation énergétique. A l'avenir, ces travaux pourront être étendus aux réseaux de distribution en basse et moyenne tension, pour le développement et l'optimisation des réseaux d'énergie intelligents, ou Smart Grids

Electromagnetic compatibility of power line communication systems

The power system has been used for communication purposes for many decades, although it was mainly the power utility companies that used low bit rates for control and monitoring purposes. In the last ten years, however, the deregulation of the power and telecommunication markets has spurred the idea of using and commercializing the power networks for a range of new communication applications and services. The idea has been developed and implemented into both, narrowband and broadband systems, which are defined in terms of the operation frequency band. Depending on the frequency band, the systems over powerlines can be: Narrow-band. They use frequencies ranging from 3-148.5 kHz in Europe, with the upper frequency extending up to 500 kHz in the United States and Japan. In Europe, this frequency range is standardized by CENELEC Standard EN 50065. Broadband. The used frequency range is 1-30MHz; 1-15MHz for outdoor systems and 15-30MHz for indoor systems. In this frequency range, the standardization situation is still unclear and there exist no regulations. The developed applications and systems use different parts of the power network: medium voltage (MV) and low voltage (LV) cabling for outdoor applications and building cabling for indoor applications. These cables are designed and optimized for power transmission at frequencies of 50/60Hz and represent a hostile medium for transmissions at higher frequencies. This thesis concentrates on electromagnetic compatibility (EMC) aspects and some optimization issues of the broadband systems, currently known as Powerline Communications (PLC) or Broadband Power Line (BPL). The work presented here was preformed in the framework of the European project OPERA (http://www.ist-opera.org/). A short description of the project is given in Chapter 1. The second chapter presents the basis, introduction, description and state of the art of the topics of interest for this thesis. That chapter is divided into three parts. Each of these parts starts with a short introduction to the topic to be addressed. The introductions are intended for those not familiar with the topic at hand and they can be skipped by those already knowledgeable of it. The first part of Chapter 2 gives an overview and introduction to telecommunication issues relevant to the thesis, as well as the general technical specifications of the OPERA system. The second part deals with the transmission medium which, for the case of PLC, is the power system. The fundamentals and the different components of the PLC system are given there and the state of the art regarding the transmission channel is presented. The third part deals with the EMC and standardization issues related to the technology. The main contributions of the thesis are presented in chapters 3 to 7. The PLC technology distinguishes itself from other technologies in that it uses already existing, ubiquitous wiring, so that no new infrastructure is needed. On the other hand, using a channel designed originally for other purposes means that it is not optimized for the frequencies and applications of interest for broadband transmission. If PLC is to compete with other technologies, these problems have to be well understood and solved, so that the system can be optimized by taking into account the parameters and constrains of the already existing medium. Although the PLC system is being improved continuously, there are still concerns about emissions, immunity and standardization. These issues are important since PLC operates in an environment already populated by other services at the same frequencies, so that fair co-existence is needed. Moreover, the PLC modem has a combined mains and telecom port and, as a consequence, the standards for conducted emissions from those two types of ports are not directly applicable. In addition, the symmetry of the cables used is low and, therefore, emissions are higher than, for example, emissions from twisted pair cables used in xDSL. A good understanding of emissions and immunity in PLC systems is therefore of great importance for the optimization of the system and for EMC standardization to be based on objective technical criteria. Even if the basic phenomena are essentially the same as for any other wire transmission system, the complexity and variability of the topologies of existing structures is so large that simple, straightforward solutions are often not applicable. Emissions from the cabling are primarily due to the common mode signals. Part of the energy in this mode is injected by the imperfectly balanced output stages of the PLC modems themselves. In addition, the common mode appears at punctual imbalanced discontinuities and distributed asymmetry along the PLC signal path in the power cables. Chapter 3 presents the work performed to improve our understanding of the sources of the common-mode current and the parameters that influence its behavior, including related measurements and simulations. For the purpose of this study, a model house was built at the EPFL's test site. Different cablings were used to study the influence of different parameters on the behavior of the common-mode current since it is the main source for both types of emissions, conducted and radiated ones. The influence of different parameters such as the cable terminations, the symmetry of the termination, the height of the conductors above the ground, the presence of power outlets, switches, empty and occupied sockets and the topology, are analyzed. The data are also used to test two methods used to simulate the differential-to-common-mode conversion and the conducted emissions, namely the transmission line model and the full wave approach provided by the Method of Moments through the Numerical Electromagnetic Code (NEC). In Chapter 4, problems related to PLC immunity testing are treated. We show that the conversion of the differential mode to the common mode is coupled with the reverse conversion by reciprocity. Due to the low symmetry of PLC cabling, part of the injected common mode test signal is converted into a differential mode signal that interferes with the wanted signal at the input of the modem being tested. Depending on the actual symmetry of the Coupling-Decoupling Network (CDN), not specified in the standards, the immunity test may yield erroneous results due to the effect of this differential mode component. Working under the assumption that the CDN is built to exhibit a symmetry similar to that of PLC networks as inferred from its longitudinal conversion loss, we estimate the differential mode disturbance level that the modems should withstand from a narrowband interferer. The bit error rate induced by the presence of the disturbing differential mode current from the CDN is also estimated, for a total physical channel transmission rate of 200 Mbps, to be of the order of 1×10-5 to 5×10-5. Since these rates can be handled by error correcting coding and MAC ARQ procedures, it is concluded that the modems are not likely to suffer any severe performance degradation due to immunity testing if the CDN exhibits a symmetry similar to that of PLC networks. Simulating the complete PLC network or any significant part of it using numerical techniques such as the method of moments proves to be of limited practical use due to the fact that PLC networks extend over many wavelengths. The transmission line approximation, on the other hand, although more efficient and sufficiently accurate for differential mode calculations, is not directly applicable to simulate the EMC behavior since it neglects the antenna-mode currents that are significant contributors to the radiated emissions. Chapter 5 presents a novel approach to evaluate the antenna-mode currents using a modified transmission line theory, thus making this numerically efficient technique applicable to the estimation of emissions in PLC. An integral equation describing the antenna-mode currents along a two-wire transmission line is derived. It is further shown that, when the line cross-sectional dimensions are electrically small, the integral equation reduces to a pair of transmission line-like equations with equivalent line parameters (per-unit-length inductance and capacitance). The derived equations make it possible to compute the antenna mode currents using a traditional transmission line code with appropriate parameters. The derived equations are tested versus numerical results obtained using NEC and reasonably good agreement is found. Another important EMC issue related to PLC is the mitigation of emissions. Chapter 6 describes a technique that has been proposed to achieve a reduction of emissions associated with indoor PLC networks through the introduction of a 180° out-of-phase replica of the PLC signal into the unused neutral-ground circuit. A modification to this technique is proposed based on the selection of the appropriate amplitude and phase of the auxiliary signal, allowing a higher degree of field attenuation. A way of implementing this technique is proposed and studied, namely the integration of a required antenna into the PLC modems themselves. The measured fields very close to the modem allow the determination of the magnitude and phase of the compensation voltage. The proposed implementation should be used only to handle customer complaints, when emissions should be lowered at locations where PLC signals might cause unwanted interference or when additional capacity is required and it can be obtained through the gained signal to noise margin. Although, in principle, due to nonalignment of the wanted and the compensation field directions, minimizing one component of the field may result in an increase of the other components, we show that the application of the technique results in an overall average reduction of 10-20 dB of all the field components in the region of interest. In the same Chapter 6, we address the more general issue of the application of mitigation techniques' gained emissions margin to increase the overall throughput of PLC systems. We show that an increase in the signal power (made possible by the inclusion of mitigation techniques) leads to a considerable increase in the PLC channel capacity. Using a number of simplifications, we show that the capacity of the channel can indeed be increased by up to 66 Mbps for mitigation efficiencies of only 10 dB. We also present the results of laboratory measurements aimed at studying, under controlled conditions, different characteristics of notching in OPERA PLC modems, such as total and effective notch width, notch depth, maximum notch depth, etc. These measurements show that it is possible to obtain attenuations of up to about 45 dB for notches in all frequency bands, 10MHz, 20MHz and 30MHz. What differs for these three bands is the minimum number of carriers that need to be notched to obtain that maximum attenuation. This is an important point, since, to implement notches that have the required depth and width, one must know how many subcarriers to suppress and how deep these need to be reduced. High density PLC deployment requires the increase of overall system data rate. To achieve the higher data rates, frequency reuse in these systems is needed. In Chapter 7, we present the idea for using so-called blocking filters as a possible solution for a frequency reuse. Experimental data obtained on a real distribution network show that the use of blocking filters can, in certain cases, ensure high enough RF separation of the LV feeders belonging to the same substation. In some cases, even with the possibility to design and integrate effective blocking filters, the system needs to provide additional synchronization mechanisms for frequency reuse

Wings in Orbit: Scientific and Engineering Legacies of the Space Shuttle, 1971-2010

The Space Shuttle is an engineering marvel perhaps only exceeded by the station itself. The shuttle was based on the technology of the 1960s and early 1970s. It had to overcome significant challenges to make it reusable. Perhaps the greatest challenges were the main engines and the Thermal Protection System. The program has seen terrible tragedy in its 3 decades of operation, yet it has also seen marvelous success. One of the most notable successes is the Hubble Space Telescope, a program that would have been a failure without the shuttle's capability to rendezvous, capture, repair, as well as upgrade. Now Hubble is a shining example of success admired by people around the world. As the program comes to a close, it is important to capture the legacy of the shuttle for future generations. That is what "Wings In Orbit" does for space fans, students, engineers, and scientists. This book, written by the men and women who made the program possible, will serve as an excellent reference for building future space vehicles. We are proud to have played a small part in making it happen. Our journey to document the scientific and engineering accomplishments of this magnificent winged vehicle began with an audacious proposal: to capture the passion of those who devoted their energies to its success while answering the question "What are the most significant accomplishments?" of the longestoperating human spaceflight program in our nation s history. This is intended to be an honest, accurate, and easily understandable account of the research and innovation accomplished during the era