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From nwokolo eric onyekachi(mini project 492) From nwokolo eric onyekachi(mini project 492) Document Transcript

  • CERTIFICATION PAGE This is to certify that I am responsible for the work submitted in this miniproject, and the original work submitted therein has not been submitted to thisdepartment for the course EEE 492 NWOKOLO, ERIC ONYEKACHI 2008/158226 DATE: -------------------------------------
  • APPROVAL PAGE This mini project has been approved by the Department of ElectricalEngineering, faculty of Engineering, University of Nigeria, Nsukka. BY ---------------------------------- -------------------------------- Engr. M. J. MBUNWE Date (Project supervisor) ---------------------------------- -------------------------------- Engr. C. A. NWOSU Date (Mini Project Co-ordinator) ……………………………… …………………………. ENGR. DR. B.O. ANYAKA Date (Head of Department)
  • DEDICATION This work is dedicated to the almighty God that gives me the strength towrite this work and the inspiration he endowed on me in the course of writingthis mini project. Also it is dedicated to the entire family of Mr. and Mrs.Nwokolo B.I. for their immense support in the course of writing this work bothfinancially and otherwise. More so, it is dedicated to my friends, well wisherswho have in one way or the other helped me in organizing and making this worksuccessful.
  • ACKNOWLEGMENTS First of all I recognize the strength and wisdom God has bestowed on meto see this work (mini project) come to reality. A work of this nature cannot becomplete without the supports receive from people of good will. I owe a lot tothose noble men and women. Among them is my project supervisor, Engr M.J.Mbunwe, a highly principled somebody. Gratitude is a debt we owe and remainsone that must be settled. My gratitude also goes to scholars I made reference totheir work. I also thank my father, Mr. Nwokolo B.I. and my mother, Mrs. NwokoloR., my elder sister Mrs. Ozor N.V., onyinye, chidera, udoka (my sisters) andikechukwu (my younger brother) for their understanding and patience in neglectof family affairs during this research. Thanks a million times.
  • ABSTRACTAn aging and inadequate power grid is now widely seen as among the greatestobstacles to efforts to restructure power system markets. In light of new andintensifying pressures on the nation’s power infrastructure, industry and policyleaders are looking to new technology solutions to increase the capacity andflexibility of the grid without further raising system voltages. High TemperatureSuperconductor (HTS) cable is regarded as one of the most promising newtechnologies to address these issues. Among HTS cable designs, one in particular– shielded cold dielectric cable – offers performance advantages particularly wellsuited to today’s siting, reliability and performance challenges. Shielded colddielectric HTS transmission cables feature very close spacing between theconductor and shield layers of wire in a coaxial cable. This close spacing result inseveral advantages: lower electrical losses; the virtual elimination of stray EMF;and significantly lower impedance than conventional cables and lines. Cablessuited for distribution-voltage, high-current applications exhibit similar benefits;including the HTS cables design which make it possible to control power flowsover HTS circuits .
  • TABLE OF CONTENTSCertification page…………………………………………………….. iiApproval page………………………………………………………… iiiTitle page……………………………………………………………….. ivDedication……………………………………………………………… vAcknowledgement……………………………………………………… viAbstract………………………………………………………………….. viiTable of contents……………………………………………………… viiiCHAPTER ONE:1.0Introduction…………………………………………………………. 11.1Purpose of the study………………………………………………… 31.2Statement of the problem…………………………………………… 31.3Limitation of the study……………………………………………. 4CHAPTER TWO:2.0 Literature review…………………………………………………… 52.1Superconductor material……………………………………………… 82.2 Special Properties of super conductor ………………………………. 92.3 High temperature super conductor cable architectures……………… 102.4Comparison between Superconductor and Other Conductors……….. 12CHAPTER THREE:3.0 Methodology……………………………………………………… 133.1 Area of study……………………………………………………… 13
  • 3.2 Instrument for data collection…………………………………….. 133.3 Methods of data collection……………………………………….. 133.4 Methods of data analysis…………………………………………. 143.5Applications of high temperature superconductor in power system…… 143.6Benefits of superconductors in power system…………………………. 22CHAPTER FOUR4.0 Discussion…………………………………………………………..... 284.1 Outcome of case studies……………………………………………… 294.2 Analysis of the research………………………………………………. 334.3 Cost of the research …………………………………………………. 37CHAPTER FIVE5.1 Conclusions…………………………………………………………… 395.2 Recommendations …………………………………………………… 40REFERENCES.APPENDIXES.
  • CHAPTER ONE1.0 INTRODUCTION Superconductivity is a unique and powerful phenomenon of nature. Nearlya century after its first discovery, its full commercial potential is just beginning tobe exploited. It is widely regarded as one of the great scientific discoveries of the20th Century. This miraculous property causes certain materials, at lowtemperatures, to lose nearly all resistance to the flow of electricity [1]. This stateof approximately zero loss enables a range of innovative technology applications.At the dawn of the 21st century, superconductivity forms the basis for newcommercial products that are transforming our economy and daily life.Superconductor-based products are extremely environmentally friendly comparedto their conventional counterparts [1]. They generate no greenhouse gases and arecooled by non-flammable liquid nitrogen (nitrogen comprises 80% of ouratmosphere) as opposed to conventional oil coolants that are both flammable andtoxic. They are also typically at least 50% smaller and lighter than equivalentconventional units which translate into economic incentives. These benefits havegiven rise to the ongoing development of many new applications in the electricpower system sector. However, superconductors enable a variety of applications to aid our agingand heavily burdened electric power infrastructure - for example, in generators,transformers, underground cables, synchronous condensers and fault current
  • limiters. The high power density and electrical efficiency of superconductor wireresults in highly compact, powerful devices and systems that are more reliable,efficient, and environmentally harmless [1]. More so, an aging and inadequate power grid is now widely seen amongthe greatest obstacles to restructure power markets. Utilities and users faceseveral converging pressures, including steady load growth, unplanned additionsof new distribution capacity, rising reliability requirements, and stringent barriersto sitting new facilities, particularly extra-high voltage (EHV) equipment [2]. Inlight of persistent challenges to proposals for conventional grid expansion, andthe recognition that industry reforms cannot succeed without renewed gridinvestment, new technologies that can increase the attention are now becoming inview. Interest in new, low-profile technologies to solve grid reliability problemsintensified as a result of frequent blackout in the nation which highlighted theimportance of power system reliability and the extent to which the margin forerror in this critical system has been eroded by falling investment and otherfactors [2]. Moreover, one of the technologies with the greatest promise to address theproblem of power system is the high capacity, high-temperature superconductor(HTS) cable which is capable of serving very large power requirements atmedium and high-voltage ratings. Over the past decade, several HTS cabledesigns have been developed and demonstrated. All of these cables have a muchhigher power density than copper-based cables or other convectional conductor.
  • Hence, because they are actively cooled and thermally independent of thesurrounding environment, they can be fit into more compact installations thanconventional copper cables, without concern for spacing or special backfillmaterials to assure dissipation of heat. This advantage reduces environmentalimpacts and enables compact cable installations with three to five times moreenough than conventional circuits at the same or lower voltage [3]. In addition,HTS cables exhibit much lower resistive losses (approximately zero) than occurwith conventional copper or aluminum conductors. Despite these similarities,important distinctions do exist among the various HTS cable designs.1.1 PURPOSE OF THE STUDY There are many applications of high temperature superconductor whichinclude: electric power, transportation, medicine, industry, communication, andScientific Research. In this work, the purpose or goal of this study is to find outapplication of high temperature superconductors and its benefits in power systemtransmission.1.2 STATEMENT OF THE PROBLEM An aging and inadequate power grid is now widely seen among thegreatest obstacles in efforts to restructure power system markets. In light of newand intensifying pressures on the nation’s power infrastructure, industry andpolicy leaders are looking to new technology solutions to increase the capacityand flexibility of the grid. Thus, the need to know the applications of High
  • Temperature Superconductor (HTS) cable since it is regarded as one of the mostpromising new technologies to address these issues in power systemtransmission. These problems of power system include: overloading of thecables, problem of siting new lines, issue of moving power safely andefficiently, carbon free electric power, instability of power, unacceptably highpower surges.1.3 LIMITATION OF THE STUDY There are many applications of high temperature superconductor and theirbenefits in different fields as a result of its unique characteristics. In electronic,the low microwave losses of HTS thin films enables the coupling of anunprecedentedly large number of resonators to microwave filter devices withmuch sharper frequency characteristics than conventional compact filters, inmilitary, in aircraft electronics, for better rejection of interference noise in aircraftradar systems, in mobile phone communication systems, HTS microwave filtersubsystems are already a commercially available solution for problematic radioreception situations, as in sensors, magnets, Power applications [1]. Hence, ourstudy here will be limited on the application of high temperature superconductorand their benefits in power system transmission.
  • CHAPTER TWO2.0 LITERATURE REVIEW In 1911, H. K. Onnes, a Dutch physicist, discovered superconductivity bycooling mercury metal to extremely low temperature and observing that the metalexhibited approximately zero resistance to electric current. Prior to 1973 manyother metals and metal alloys were found to be superconductors at temperaturesbelow -249.8oC [1]. These became known as Low Temperature Superconductor(LTS) materials. Since the 1960s a Niobium-Titanium (Ni-Ti) alloy has been thematerial of choice for commercial superconducting magnets. More recently, abrittle Niobium-Tin inter-metallic material emerged as an excellent alternative toachieve even higher magnetic field strength. In 1986, J. G. Bednorz and K. A.Muller discovered oxide based ceramic materials that demonstratedsuperconducting properties as high as -238oC. This was quickly followed in early1997 by the announcement by C. W. Chu of a cuprate superconductorfunctioning above -196oC the boiling point of liquid nitrogen. Since then,extensive research worldwide has uncovered many more oxide basedsuperconductors with potential manufacturability benefits and criticaltemperatures as high as -1380C. Hence, a superconducting material with a critical temperature above-249.8oC is known as a High Temperature Superconductor (HTS), despite the continuing need for cryogenicrefrigeration for any application. High-temperature superconducting (HTS) cable,characterized by high current density and low transmission loss, shows promise
  • as a compact large-capacity power cable that exhibits several environmentaladvantages such as energy and resource conservations as well as no externalelectromagnetic fields [1]. It must be noted that the “approximate zero resistance”ascribed to HTS material applies to the transmission of direct current (DC)power, while there is some electricity loss involved in AC transmission. HTS DCcable takes maximum advantage of the characteristics of superconductivity [4]. Fig 1: Transition in Superconductor Discoveries [1]However, there are absent of those problems unique to AC applications, HTSDC cables are expected to outpace HTS AC cables, in line with futureperformance enhancement and price reduction of converters. However, thediagram above shows the transition in superconductor discoveries starting from1911 through 2010 [1].However, there are some challenges that are often encountered in the use ofsuperconductor in power system which include:
  •  Cost  Refrigeration  Reliability  Acceptance More so, many years of development and commercialization of applicationsinvolving LTS materials have demonstrated that a superconductor approachworks best when; it represents a unique solution to the need. Alternatively, as thecost of the superconductor will always be substantially higher than that of aconventional conductor in the field of power system, it must bring overwhelmingcost effectiveness to the system. The advent of HTS has changed the dynamic ofrefrigeration by permitting smaller and more efficient system cooling for someapplications [1]. Moreover, design, integration of superconducting and cryogenic technologies(at very low temperature)demonstration of systems cost benefits and long term reliability must be met before superconductivity delivers onits current promise of major societal benefits and makes substantial commercial inroads into new applications. Itis widely regarded as one of the great scientific discoveries of the 20th Century. This miraculous property causescertain materials, at low temperatures, to lose all resistance to the flow of electricity. This state of approximatelyzero loss enables a range of innovative technology applications. At the dawn of the 21st century,superconductivity forms the basis for new commercial products that are transforming our economy and daily life.However, Current Commercial applications of superconductors include the following [1]:  Magnetic Resonance Imaging (MRI)  Nuclear Magnetic Resonance (NMR)  High-energy physics accelerators  Plasma fusion reactors
  •  Industrial magnetic separation of kaolin clay Hence the major commercial applications of superconductivity in the medical diagnostic, science andindustrial processing fields listed above all involve LTS materials and relatively high field magnets. Indeed,without superconducting technology most of these applications would not be viable. Several smaller applicationsutilizing LTS materials have also been commercialized, example, research magnets and Magneto-Electroencephalography (MEG); the latter is based on Superconducting Quantum Interference Device (SQUID)technology which detects and measures the weak magnetic fields generated by the brain. The only substantivecommercial products incorporating HTS materials are electronic filters used in wireless base stations. About10,000 units have been installed in wireless networks worldwide to date [1].2.1 SUPERCONDUCTOR MATERIAL A Superconductor material differs fundamentally in quantum physicsbehavior from conventional materials in the manner by which electrons orelectric current move through the material. It is these differences that give rise tothe special properties and performance benefits that differentiate superconductorsfrom all other known conductors [1]. A superconductor is an element or metallicalloy which, when cooled to near absolute zero, dramatically lose all electricalresistance. In principle, superconductors can allow electrical current to flowwithout any energy loss (although, in practice, an ideal superconductor is veryhard to produce). In addition, superconductors exhibit the Meissner effect inwhich they cancel all magnetic flux inside, becoming perfectly diamagnetic(discovered in 1933). In this case, the magnetic field lines actually travel aroundthe cooled superconductor. It is this property of superconductors which isfrequently used in magnetic levitation experiments.2.2 SPECIAL PROPERTIES OF SUPERCONDUCTOR MATERIALS
  • Approximately zero resistance and high current density have a major impacton electric power transmission and also enable much smaller or more powerfulmagnets for motors, generators, energy storage, medical equipment and industrialseparations. Low resistance at high frequencies and extremely low signaldispersion are key aspects in microwave components, communicationstechnology and several military applications [1]. Low resistance at higherfrequencies also reduces substantially the challenges inherent to miniaturizationbrought about by resistivity. The high sensitivity of superconductors to magneticfield provides a unique sensing capability, in many cases 100 percent superior totoday’s best conventional measurement technology. Magnetic field exclusion isimportant in multi-layer electronic component miniaturization, provides amechanism for magnetic levitation and enables magnetic field containment ofcharged particles. The final two properties form the basis for digital electronicsand high speed computing well beyond the theoretical limits projected forsemiconductors. All of these materials properties have been extensivelydemonstrated throughout the world. These properties of superconductor can besummarized under the following points [1]:  Zero resistance to direct current  Extremely high current carrying density  Extremely low resistance at high frequencies  Extremely low signal dispersion
  •  High sensitivity to magnetic field  Exclusion of externally applied magnetic field  Rapid single flux quantum transfer  Close to speed of light signal transmission.2.3 HIGH TEMPERATURE SUPERCONDUCTOR CABLE ARCHITECTURES Interest in the field of superconducting power cable dates to the 1960’s, butbecause conventional metallic superconductors required cooling with liquidhelium, these cable system designs were excessively complex and cost-prohibitive. Interest in the field was renewed following the discovery ofceramics-based high-temperature superconductors in the late 1980’s, whichenabled the use of liquid nitrogen as a cooling medium. Liquid nitrogen is widelyused in a variety of industrial applications and is recognized as a cheap, abundantand environmentally harmless coolant [2]. Over the past several decades, a variety of cable designs were prototypedand developed to take advantage of the efficiency and operational benefits ofsuperconductivity, while minimizing the additional capital and operating coststhat result from the requirement that HTS cables be refrigerated. Variations incable architecture have important implications in terms of efficiency, strayelectromagnetic field (EMF) generation, and reactive power (Volt AmpereReactive or VAR) characteristics. At present there are two principal types of HTS
  • cable. The simpler design is based on a single conductor, consisting of HTS wires stranded around a flexible core in a channel filled with liquid nitrogen coolant [2]. This cable design employs an outer dielectric insulation layer at room temperature, and is commonly referred to as a "warm dielectric" design. It offers high power density and uses the least amount of HTS wire for a given level ofFigure 1. Single-phase warm-dielectric cable Figure 2. Single-phase cold-dielectric cable power transfer. Drawbacks of this design relative to other superconductor cable designs include higher electrical losses (and therefore a requirement for cooling stations at closer intervals), higher inductance, required phase separation to limit the effects of eddy current heating and control the production of stray electromagnetic fields (EMF) in the vicinity of the cable. Most of the HTS cable demonstrations undertaken to date have been based on the warm dielectric design. An alternative design employs concentric layer(s) of HTS wire and a cold electrical insulation system. Liquid nitrogen coolant flows over and between both layers of wire, providing both cooling and dielectric insulation between the center conductor layer and the outer shield layer. This is commonly referred to as a coaxial, "cold dielectric" design. Cold dielectric HTS cable offers several important advantages, including higher current carrying capacity; reduced AC losses; low inductance; and the complete suppression of stray electromagnetic fields (EMF) outside of the cable assembly. The reduction of AC losses enables wider spacing of cooling stations and the auxiliary power equipment required to assure their reliable operation [2].
  • 2.4 COMPARISM BETWEEN SUPERCONDUCTOR AND OTHER CONDUCTORS Normal conductors have resistance which restricts the flow of electricityand wastes some of the energy as heat. The resistance increases with the length ofthe conductor. Superconductors have close to zero or zero resistance and a fewother properties, but the resistance is the most important one because it meanselectricity can flow more efficiently through it. The drawback is that all thesuperconductors we know of today have to be cooled down to extremely lowtemperatures to achieve superconductivity [5]. CHAPTER THREE3.0 METHODOLOGY This chapter describes the procedures or steps adopted while carrying out the study. It isdiscussed under the following points: area of study, instrument for data collection, method of data collection andmethod of data analysis.3.1 AREA OF STUDY The area of study of this work has been chosen to be United States powersystem grid. A superconductor application is still a young technology and has not been practiced in Nigeria.3.2 INSTRUMENT FOR DATA COLLECTION The researcher has chosen to consult the works of other scholars mainly.This was taken due to lack of time and necessary materials for experimentation.The option of structured questionnaire was avoided because the researcher could not
  • tour all round the area chosen due to logistic constraints. Also this instrument will be easy in terms of datacollection.3.3 METHODS OF DATA COLLECTION The researcher collected data for this study through visiting the internetand works of scholars online, visiting the library to read books written by well know writers.Data were also sourced using computer software like Encarta premium. The writer did not relent to havediscussion with colleagues in order to verify facts.3.4 METHOD OF DATA ANALYSIS The method the researcher used in analyzing data is data comparison. Theresearcher gets information from different authors, compares them and uses the results to drawout conclusion.3.5 APPLICATIONS OF HIGH TEMPERATURE SUPERCONDUCTORIN POWER TRANSMISSION Today’s power grid operators face complex challenges that threatentheir ability to provide reliable service; steady demand growth; aginginfrastructure; mounting obstacles to sitting new plants and lines; and newuncertainties brought on by structural and regulatory reforms. Advances in hightemperature superconductivity (HTS) over the past two decades are yielding anew set of technology tools to renew this critical infrastructure, and to enhancethe capacity, reliability and efficiency, of the nation’s power system. Powerindustry experts in the United States have widely agreed that today’s aging powergrid must be strengthened and modernized. Utilities must cope with a growth in
  • the underlying level of demand driven by our expanding, high technology-intensive economy [1]. Consumers in the digital age have rising expectations and requirements forgrid reliability and power quality. Competitive reforms have brought about newpatterns of power flows. EPRI (The Electric Power Research Institute) hasestimated that huge amount of resources must be spent over the next ten years toachieve and maintain acceptable levels of electric reliability. At the same time,utility shareholders are insisting on strong financial performance and moreintensive use of existing utility assets. Moreover, gaining approval to site new infrastructure - both generatingplants as well as transmission lines - has become extremely difficult in the face oflandowner and community opposition and the NIMBY (“not in my back yard”)phenomenon. This is especially the case in urbanized areas where power needsare concentrated. As a result, utilities face lengthy and uncertain planninghorizons, as well as a rising risk of costly blackouts and other reliabilityproblems. The existing grid is also becoming increasingly regionalized with moregeneration located remotely to be close to its particular source of fuel. The gridwill therefore have to mitigate increasing inter-regional fault current transfers andthe increasing number of parallel transmission paths that will be required to allowlowest cost electricity to flow to where it is needed and to allow a smarter grid toquickly respond to disruptions of sources, transmission or local generation paths[1].
  • Distributed generation can help but is not always available when needed, andalso must be redesigned, possibly with the help of fault current limiters, to ridethrough local fault and remain available. Solving this complex set of problemswill require a combination of new policies and technologies. Regulatory reformsare needed to foster stronger incentives for grid investment and to overcome thefragmentation that has impeded utilities ability to raise the required investmentcapital. Beyond all this new rules, however, the physical nature of the challengerequires the adoption of advanced grid technologies, including those based onHTS. These new HTS technologies have undergone rapid development in thecomparatively short time of two decades. The first HTS compounds weresynthesized in research laboratories in the late 1980s. Today, the HTS industryhas advanced to full-scale power equipment prototypes and demonstrationprojects that are undergoing the rigors of in-grid evaluation. As these newtechnologies are incorporated into the existing power system, they will offerutilities new tools to ease the pressures that limit the performance and capacity oftheir systems – with much lower space and land use impacts and with majorenvironmental benefits that are available using traditional grid upgrade solutions[1].3.5.1 HIGH TEMPERATURE SUPERCONDUCTOR WIRE The foundation of these applications is a new generation of wire capable ofcarrying vastly (on the order of 100 percent times) higher currents than
  • conventional copper wires of the same dimension, with approximately zero ornegligible resistive losses. Today’s prototype and demonstration technologieshave made use of a proven, readily available and high-performance firstgeneration HTS wire that is multi-filamentary in composition. Second generation(2G) HTS wire, using coated conductor architecture and a variety of thin filmmanufacturing processes, is rapidly making its way to market. 2G wire willgreatly broaden the addressable market for existing HTS devices because of itspredicted lower cost. It will also enable altogether new types of HTS applicationsdue to its superior performance characteristics in certain modes of operation. 2Gwire has been commercially available since 2006. HTS wire, in short, brings thepromise of a revolution in the way electricity is generated, delivered andconsumed - much as the introduction of optical fiber led to a technological leapforward in the telecommunications industry. Among the power systemapplications of HTS wire enables are the following:3.5.2 HIGH TEMPERATURE SUPERCONDUCTOR POWER CABLESToday’s conventional power lines and cables are being operated closer to theirthermal limits, and new lines are becoming hard to site. Compact, high-capacityunderground HTS cables offer an important new tool for boosting grid capacity.Today’s advanced HTS cable designs enable controllable power flows and thecomplete suppression of stray EMF.HTS power cables transmit 3-5 times morepower than conventional copper cables of equivalent cross section, enabling moreeffective use of limited and costly rights-of-way. Significant progress toward the
  • commercialization of HTS cable is underway. Three major in-griddemonstrations have been completed in the US including the world’s first HTSpower transmission cable system in a commercial power grid which is capable oftransmitting up to 574 megawatts (MW) of electricity, enough to power 300,000homes. Two more demonstrations are in the planning stage in the US and anotherdozen projects are active around the world [1].3.5.3 HIGH TEMPERATURES TRANSFORMERSGrid operators face a major challenge in moving power safely and efficiently,from generators to consumers, through several stages of voltage transformation.At each stage, valuable energy is lost in the form of waste heat. Moreover, whiledemands are continually rising, space for transformers and substations -especially in dense urban areas - is severely limited. Conventional oil-cooledtransformers also pose a fire and environmental hazard. Compact, efficient HTStransformers, by contrast, are cooled by safe, abundant and environmentallyharmless liquid nitrogen. As an additional benefit, these actively-cooled deviceswill offer the capability of operating in overload, to twice the nameplate rating,without any loss of life to meet occasional utility peak load demands [1].3.5.4 HIGH TEMPERATURE SUPERCONDUCTOR TRANSFORMERSFOR WIND ENERGYThe increasing demand for clean, carbon free electric power, coupled with theglobal warming crisis, has fueled tremendous interest in and development of
  • renewable energy technologies such as wind power. To break through theeconomic barrier and ensure the future of this vast and critically important greenenergy source, new technologies are needed offering lower weight, higherefficiency, and significantly improved reliability. Direct drive wind generatorsare utilizing a new high-efficiency stator design and replacing copper with HTSwire on the rotor. Estimates are that a 10 MW drive utilizing HTS technologywould weigh about one third the weight of a conventional direct drive generatorwith the same power rating. This reduction in weight would also allow anincrease in blade size and greater power output. The net effect is expected todouble the power system capacity of conventional systems and lower the cost ofwind generated energy [1].3.5.5 ENERGY STORAGEWith power lines increasingly congested and prone to instability, strategicinjection of brief bursts of real power can play a crucial role in maintaining gridreliability. Small-scale Superconducting Magnetic Energy Storage (SMES)systems, based on low-temperature superconductor, have been in use for manyyears. These have been applied to enhance the capacity and reliability ofstability-constrained utility grids, as well as by large industrial user sites withsensitive, high-speed processes, to improve reliability and power quality. Largersystems, and systems employing HTS, are a focus of development. Flywheels,based on frictionless superconductor bearings, can transform electric energy intokinetic energy, store the energy in a rotating flywheel, and use the rotational
  • kinetic energy to regenerate electricity as needed. Using bulk HTS self centeringbearings allows levitation and rotation in a vacuum, thereby reducing frictionlosses. Conventional flywheels suffer energy losses of 3-5 percent per hour,whereas HTS based flywheels operate at <0.1 percent loss per hour. Large andsmall demonstration units are in operation and development [1].3.5.6 HIGH TEMPERATURE SUPERCONDUCTOR FAULT CURRENTLIMITERSAs new generators are added to the network, many local grids face a rising riskof unacceptably high power surges that result from “faults” or short circuits.These occasional surges are induced by adverse weather, falling tree limbs,traffic accidents, animal interference and other random events. As fault currentlevels rise, they pose a mounting risk that such surges will exceed the rating ofexisting conventional circuit breakers, switchgear, bus, distribution transformersand other equipment and expose grids to much more costly damage. HTStechnology enables a new solution: compact, “smart” fault current limiters(FCLs) that operate passively and automatically, as power “safety valves” toensure system reliability when individual circuits are disrupted. Taking advantageof the inherent properties of superconductors, they sense such dangerous overcurrents and reduce them to safe levels by changing state instantaneously, from“super” conductors to resistors. Several demonstrations of this breakthroughtechnology are now underway, with an expected commercial horizon of 2010 [1].
  • 3.5.7 AN ENABLER OF THE ELECTRICITY REVOLUTIONThe advent of HTS technology offers the opportunity for grid operators to moveto a new level of power system performance. Since the dawn of the utilityindustry in the late 19th century, power system networks have been based almostexclusively on components made of conventional materials such as copper,aluminum and iron. The performance and capacity of the grid has been improvedand expanded over time. Yet grid performance is ultimately limited by theinherent properties and limitations of these materials. HTS-based technologyremoves many of these operational and space constraints. It offers grid operatorsa new set of tools and strategies to improve the performance, reliability, safety,land use and environmental characteristics of a power system. The need for suchnew solutions is becoming acute with the relentless electrification of energy use -a trend that makes our aging, heavily burdened grid more critical than ever to thefunctioning of modern society. However, in many ways, the electric powerindustry is at a crossroads. Within the past few years, electric power industrystructural reform efforts have stalled perceptibly. The current gridlock in policyreforms and power flows is largely due to the mounting difficulty of expandingthe power delivery network. Without a way to expand the “superhighwaysystem” that supports power flows, recent competitive market reforms simplycannot succeed. HTS technology can play an important role in “breaking the
  • gridlock” of power flows and policy reforms that threaten the power industry andour overall economy. However, before HTS technology solutions can enjoy broad acceptance,they must undergo field trials. Such demonstrations play a crucial role inestablishing a record of reliability and working out grid integration issues.Despite the acute needs facing the power system sectors, it is widely observedthat investor-owned utilities have taken a cautious and conservative approach toadopting new technology solutions in recent years. This has resulted from severalfactors including: a perception of asymmetric regulatory risks; disallowancesresulting from past technology failures; and the loss of sites where experimentaltechnologies can be tested without potentially adverse consequences forcustomers. Industry restructuring efforts underway since the early 1990’smoreover have had the unfortunate effect of undermining investment in jointly-funded industry R&D [1].3.6 BENEFITS OF HIGH TEMPERATURE SUPERCONDUCTORS INPOWER TRANSMISSIONUsing high temperature superconductor in power transmission can translate intosignificant cost savings. The factors that lead to lower costs on an installedsystem basis may be summarized as follows:3.6.1 SHORTER LENGTHS
  • Short, strategic insertions of HTS cable could achieve the same power flowbenefit as lengthier circuits of overhead line. HTS cable need not be cost-competitive with conventional cable or overhead line technology on a stand-alonebasis for it to offer a lower total cost solution. For example, with HTS cableutilities may solve power flow problems with shorter circuit lengths, e.g.,connecting to the more pervasive 11/33/66 Kv system rather than tying back tothe more distant EHV backbone transmission system [3].3.6.2 LOWER VOLTAGESBecause of the higher capacity of HTS cable (approximately three to five timeshigher than conventional circuits), utilities may employ lower-voltage equipment,avoiding both the electrical (I²R) losses typical of high-current operation and thecapital costs of step-up and step-down transformers (as well as the no-load losseswithin the transformers themselves). High-current HTS cables at 33 kV or even11 kV may solve problems that would ordinarily require a 132 kV or 330 kVconventional solution. The ability to operate at lower voltages translates intolower costs for cable dielectric/insulating equipment, reduced hazards, as well aslower cable and ancillary costs, which are driven by the voltage level of theselected solution. In the long run, HTS may make unnecessary the much highersystem costs (e.g., transformer and breaker replacement) associated with wide-area voltage up-ratings [3].3.6.3 GREATER CONTROLLABILITY
  • HTS cable offers the ability to control power flows with conventional seriesreactors, yielding market and reliability benefits typically associated with other"controllable" forms of transmission e.g., FACTS (Flexible AC TransmissionSystems) or DC transmission. Yet this control at the terminal of a line would beachieved with much less expense and complexity than is typically required usingconventional technologies (e.g., large, inflexible DC converter stations or thelarge-scale power electronic devices often associated with conventional FACTSdevices). Whereas DC lines are limited to point-to-point flows, HTS cablesystems could be expanded to provide controllability to many points in anetwork. This inherent controllability has important regulatory implications. Forexample, HTS could form the basis for private, at-risk investment in merchanttransmission projects with assignable property rights in transmission capacity,outside of the rate base framework, in situations where DC and conventionalFACTS solutions are not cost-competitive. The cost of DC systems is highlyimpacted by the cost of converter stations. For short runs of DC transmission,system costs are dominated by the cost of converter stations; HTS cables face nosuch penalty [3]. 3.6.4 LIFE EXTENSION AND IMPROVED ASSET UTILIZATIONHTS cable represents a new weapon to attack the principal enemy of congestedurban transmission systems: heat. Over time, thermal overload ages and degradescable insulation. By drawing flow away from overtaxed cables and lines,
  • strategic insertions of HTS cable can "take the heat off" urban power deliverynetworks that are increasingly prone to overheating, the inevitable result ofincreased loadings and acute siting difficulties associated with sitingconventional (copper or aluminum-based) system expansions. Reducing theburden on existing electrical pathways will extend the life of conventional systemelements. This approach also improves overall asset utilization, and defers theneed for the large-scale capital investment required for the replacement of agingand worn-out grid infrastructure [3].3.6.5 EXPANDED GENERATOR SITING OPTIONS Because it greatly reduces voltage drop, HTS cable has the ability to "shrinkelectrical distance". This means that new generators could be located at greaterdistance from urban loads (where land, labor and other costs are lower), whileproviding the same degree of voltage support as if they were located in oradjacent to the city center. Thus, HTS transmission lines could be deployed as"virtual generators" to solve both power supply and reactive power problems [3].3.6.6 REDUCED ELECTRICAL LOSSESIn specially optimized designs, cable can result in lower net energy losses thanoccur in either conventional lines and cables or unshielded HTS cables with asingle conductor per phase, offering a transmission path with high electricalefficiency. Because HTS circuits tend to attract power flow, they will naturally
  • operate at a high capacity factor, reducing the losses on other circuits and furthermagnifying their efficiency advantage [3].3.6.7 INDIRECT AND NON-MONETARY SAVINGS In addition to these "hard cost" savings, HTS cable may result in other "softcost" savings. For example, time to install may be shortened because of reducedsiting obstacles associated with compact underground installations and lessburdensome siting requirements for lower-voltage facilities. HTS cables might berouted through existing, retired underground gas, oil or water pipes, throughexisting (active or inactive) electrical conduit, along highway or railway rights-of-way, or through other existing corridors. While HTS cables “off-the-shelf” arelikely to cost more than conventional cables, the net cost of a fully installed cablesystem may be lower because of the smaller space requirements associated withHTS cables, and the ability to make adaptive reuse of existing infrastructurewhere it exists, or the ability to use guided boring machines instead of costlierand more disruptive trenching where such infrastructure does not exist. Theexpansion of siting options would reduce the need for costly and controversialexpropriation proceedings. Indirect impacts on property values resulting fromoverhead line construction would also be avoided. Communities that host HTSprojects would gain the benefit of higher property valuations, e.g., higherproperty tax receipts and broader development options [3].3.6.8 REDUCED REGIONAL CONGESTION COSTS
  • Finally, and perhaps most significantly, the ability to complete grid upgradeprojects more quickly will translate into the earlier elimination or relaxation ofgrid bottlenecks. Solving physical bottleneck problems will sharply reduce thegrid congestion costs that, in todays unsettled, imperfectly competitivemarketplace, can impose huge penalties on consumers and the economy at large[3].3.7 ENVIRONMENTAL BENEFITSBeyond the cost advantages outlined above, HTS cable will yield severalenvironmental advantages over conventional technology. Some of theseadvantages are due to the very same characteristics of HTS cable that result inlower-cost installed solutions. For example [3]:  Underground placement: The underground placement of HTS cable will eliminate the visual impact of overhead lines.  Shorter cable lengths: Solving power flow problems with shorter lengths of cable in more compact rights-of-way will reduce the disruptive effects of construction.  Reduced losses: The reduced losses in HTS circuits, as well as reduced I²R losses on adjacent, conventional circuits that are offloaded due to the "current hogging" effects of HTS cable, will translate into reduced fuel consumption for generation.
  •  Environmentally harmless dielectric: Liquid nitrogen, the coolant/dielectric of choice for HTS cables, is inexpensive, abundant and environmentally compatible [3]. CHAPTER FOUR4.0 DISCUSSIONS The system study “Applications of High Temperature Superconductivity(HTS) and its benefits in power system transmission”, lists the applications;technical and economical benefits in power system generation, transmission anddistribution systems, and using components build up with HTS materialconsidering the state of the art in knowledge on superconductivity. Besides minimal transmission losses, the ability to carry large currentdensities is an important criterion for superconducting materials to createfavorable conditions for applications using this new technology. The currentdensities of known HTS materials are about 100A/mmsq, which is at least 10times larger compared to the current densities in conventional aluminum orcopper conductors.
  • Another interesting feature is the use of the transition from thesuperconductor to the non superconducting state of the material. This property isused for current limiting in power system. The advantages of the low energylosses compared with the actual cost of investment and maintenance do notjustify an economical application of most superconducting components in powersystem today. Therefore, additional benefits seem to be required in order toguarantee a successful implementation of superconductor in the field of electricpower applications. An example of such benefit is the integration of the currentlimiter and the superconducting transformer. This solution combines the twoelement superconducting transformer with low energy losses and current limiterin an advantageous manner. The current limiter permits then a decrease of thetransformer short circuit impedance, which one hand leads to a largertransmission capacity and on the other hand allows for an improved voltagestability at the secondary side of the transformer .These synergies lead to areduction of the investment cost, to more economical applications due tointegration as well as to an increase of energy efficiency in the transmission anddistribution system.4.1 OUT COME OF CASE STUDIES Detailed research activities are necessary to show the potential of usinghigh temperature superconductivity in the field of power system. Hence a set ofcase studies have been investigated:
  •  Increase of transmission capacity by reducing impedances  Increase of mesh of power system  Increase of quality and availability of power system  Re-dimensioning of elements used in power system  Reduction of energy losses  Reduction of environmental impacts  Increase of the dynamic stability  Integration of power production plants  Development of new switchgear concepts  Application of DC network in power system The result of the system study is categorized as discussed below (ideas, solution approaches and economical solutions).I. IDEAS The transmission capacity of a network can be increased due to the realization of a network with low ohmic, coaxial or concentrically constructed, superconducting cables and transformers. The high current capability of the HTS- cable gives in selected cases the possibility to exchange the 380kv voltage level
  • by one of 110kv. Another possibility is to keep the 380kv level for the European power system and to transform the power directly from 380kv to powerful superconducting backbone-lines in the distribution network. II. VISION If government requirements change concerning environmental impacts for the realization of overhead lines, it might be impossible to build new overhead lines and it might be mandatory to replace existing overhead lines by underground cables. HTS- cables could in such a situation, be the solution to economically transmit the increasing need of energy in the major centers with a low environmental impact. Possible scenarios are superconducting connections through road or railway tunnels in mountain areas with the aim to reduce the number of the overhead lines and to decrease transmission losses as well as a backbone solution for the transit of energy.III. ECONOMICAL SOLUTIONS The result of case studies concerning the integration of current limiters in power system show the great potential using these elements in a technically efficient manner independent of the nominal power in all voltage levels of power system. The actual production costs are difficult to calculate in detail. It must be assumed that the cost lie in a range affordable. An investment cost at the upper end of this range allows an economical use, especially in regional distribution
  • and industrial power system. An important advantage resulting from the introduction of current limiters in distribution system is the use of load breakers instead of the expensive short circuit breakers as switching devices. The main benefits of the superconducting transformers are the low energy losses, the decrease in weight and volume as well as the reduction of environmental impacts. Due to it’s the behaviors of the superconducting transformers at restart, its first economical applications are seen in urban cable networks and as blocks transformers in power plants. The integration of the current limiting function in transformers will increase number of economically advantageous applications.IV. SOLUTION APPROACHES The replacement of conventional copper cables by HTS-cables in existing ducts result in the simultaneous effect that in the same space more power with less electrical losses can be transmitted. Due to the larger current densities compared to conventional cables, superconducting cables must be constructed in a new manner. Besides the coaxial construction principle, a concentric construction principle might also be possible. With these two construction variations, the electromagnetic influence outside of the cable can be eliminated. This will be a requirement considering the expected applications of large current density. With
  • the mentioned constructions principles, it would for instance be possible tomanufacture 110kv HTS-cables with similar physical parameters andtransmission capacity as 380kv conventional overhead lines. The use ofsuperconducting cables is most promising for direct current networks. Largecurrent applications imply the possibility to eliminate some voltage levels of anelectrical network. Due to this effect, the DC superconducting cables may cost about 4 timesas much as the conventional cables. Moreover, the following conclusions areimportant from a technical point of view:Superconducting cables with nominal voltages higher than 20kv can be realizedin a technical efficient manner both for AC and DC system;The use of HTS-DC cables is economically more attractive than the applicationof HTS-AC-cables. The essential advantages are the effect of no losses in theduct and no dielectric losses as well as the very compact design. The application of the high temperature superconducting magnetic energystorage devices (SMES) is not economical compared with the flywheel. Reasonsare the physical parameters of existing BISSCO HTS-materials. These materialshave a large decrease of the critical current density in a relatively small magneticfield. If in future the HTS-material YBCO will be available, the comparison has
  • to be repeated because the stability of the magnetic field of this material is muchbetter.4.2 ANALYSIS OF THE RESARCH4.2.1 ANALYISI ON TRANSFORMER APPLICATION The basic design process for the HTS transformers is similar to that ofconventional transformers. A good design is a function of the optimal use ofactive materials such an iron-core, HTS material and cryogenic cooling system.Below are a few analyses that are significant impact on the size, weight, cost andperformance of HTS transformer.a) AC losses in HTS winding: CTC is used in the design analysis in order tominimize the AC losses in the winding. The AC losses could represent asignificant portion of the total thermal load on the refrigeration system, but noreliable analysis is available for estimating these losses while a CTC carries theAC and experiences the external AC field.IRL and others are in process ofdeveloping AC loss analysis formulations. Due to unavailability of good analysisbasis, AC losses have not been estimated for the windings.b) Size and weight: Voltage per turn is a measure of core limbs cross section.A larger core cross section may lower HTS consumption at the expense of largerweight and size. The larger core will also require bigger diameter coils. However,a manufacturer may prefer winding diameter no larger than what their existing
  • machinery can handle. Thus, by keeping the core diameter similar to that ofconventional transformers, it is possible to reduce the overall size and weight ofHTS transformers of similar rating. In other words a transformer manufacturecould produce HTS transformers of twice the rating within the capabilities oftheir existing winding and handling equipment and facility space. However, somecustomers may not mind the larger weight caused by the larger diameter core,provided that the product price is lower .selection between the two approaches isbetter made by discussion between a customer and a manufacturer.c) Operating temperature: A conventional oil-cooled transformer designedfor 100 degrees Celsius operation can be operated at 50 percent overload bycirculating oil in the tank and at 100 percent overload by providing additionalcooling fans. Similar ratings are also possible with HTS transformers. Forexample if an HTS transformer is designed for operation at 77k ,then it ispossible to overload it by 50 percent and 100 percent by operating it at 70k and64k, respectively. Lower temperature operation will require additional cryogeniccooling capacity.d) Operational constraints: Since HTS winding are more compact thancopper winding of a conventional transformer, the leakage reactance of HTStransformers can be designed to be low. A low leakage reactance result in loweroutput voltage variations between no –load and rated load conditions. It mightalso be possible to eliminate use of tap changers typically employed to correct
  • output voltage as a function of load. However, lower leakage reactance generateshigher through fault current and forces during a short circuit event experiencedby a transformer. Thus a compromise is needed between lower leakage reactanceand acceptable fault current.4.2.2 ANALYSIS ON FAULT CURRENT LIMITERS APPLICATION High temperature superconductor technology permits a modern solution toeliminate surge in power system transmission. This is as a result of its compactand simplicity in any system incorporated. It allows the passive and automaticallyoperated circuit as power safety valves. Also because of its transition fromsuperconductor to resistor when a high current density passed through thematerial, this particular application was able to achieve.4.2.3 ANALYSIS ON HTS POWER CABLE AND WIRE APPLICATION The basis of these particular applications is a new technology of wirecapable of carrying more than 100 percent higher currents than conventionalcables/wire of the same dimension, with approximately zero or negligibleresistive losses. Looking at Nigeria power grid, characterized by aluminum orcopper cable/wire it has being marked with low voltage as a result of its radialnetwork. In which if this HTS cable is used in the network will account for lessloss in the network and deliver equal voltage in the sending end of the powersystem4.2.4 ANALYSIS ON ENERGY STORAGE APPLICATION
  • Power system is often marked by instability of supply. SuperconductingMagnetic Energy Storage system can solve this issue based on low temperaturesuperconductor. These can been apply to enhance the capacity and reliability ofstability-constrained utility grids; For example Flywheels, based on frictionlesssuperconductor bearings, can transform electric energy into kinetic energy, storethe energy in a rotating flywheel, and use the rotational kinetic energy toregenerate electricity as needed. And this will ensure continuity in the system. Generally, the integration of high temperature superconductor in powersystem transmission is as a result of its following features which in include:environmentally harmless dielectric, reduced loss, shorter cable lengths, highlyefficient in underground placement, indirect and non-monetary savings, reducedregional congestion costs, expanded generator siting options, life extension andimproved asset utilization, greater controllability, lower voltages as the authorhas highlighted above.4.3 COST OF RESEARCH This research work is relatively expensive to the author. This is so becausethe researcher lacks the necessary material to carry out the work effectively.Hence, he relents on online material by browsing through a subscription made toGLO/MTN network using modem, thus this subscription make the workexpensive.
  • 4.4 PROBLEMS ENCOUNTERED IN THE CAUSE OF WRITING THIS RESEARCH WORK As a result of carrying out this research work the author encountered many problems which include:a. The use of high temperature superconductor is not used in Nigeria where the author is leaving, thus he could not get some information required to carry out the research work effectively.b. The usual problems of power failure also pose a great obstacle during the research work.c. The author also encountered the problem of analyzing the online material and other material collected in the cause of writing this work and putting it in a simple language that can be generally understand by anybody.d. Also the author lacks some statistical material and equipment to carry out the experimental study.
  • CHAPTER FIVE CONCLUSIONS AND RECOMMEDATION5.0 CONCLUSION Given todays acute level of concern about power system reliability andnew competitive pressures, it brings to our notice that strategies to control andredirect transmission flows have greater value than ever before. As powertransmission problems have intensified across the nations grid over the past fewyears, the need for new technology solutions has become apparent. HTS cablesconstitute new tools to develop these strategies. By taking advantage of theiroutstanding features, utilities and regional transmission operators will find newand less expensive ways to tackle grid congestion problems, reduce grid securityviolations, improve overall asset utilization and extend the life of their existingsystems.
  • Also, the widespread commercial adoption of these superconducting devices forpower networks has great potential to generate a range of economic,environmental and reliability benefits, many of which are discussed herein.Yet, as is often the case with many “breakthrough” technologies that are initiallyhigh-cost, early developers, and users face high risks. These risks arecompounded by the very uncertainties and regulatory complications that VLIcable could ultimately help to resolve. It is important, therefore, to undertake allappropriate steps to speed the commercialization of this promising technology.5.1 RECOMMENDATIONGenerally series of demonstration projects to illustrate the power flow attributesof HTS cables, to develop a reliability record for the technology, and to resolvesystem integration and other issues should be a top priority of public officialsresponsible for power system related policy.As in the case where the author is residing the new technology is not in practiceat all. Thus he urges utilities, experts and the federal government to embark onthe use of the new technology as integration in power system components so as toreduce the problems of power system in the country in which it can address asseen from this study. Which include in high temperature superconductor wire,high temperature superconductor power cables, energy storage, high temperaturestransformers and high temperature superconductor fault current limiters etc.
  • REFERENCE [1] IEEE CSC council on superconductivity, Superconductivity its present andfuture application. [2] John Howe, Very low impedance superconductor cables, concepts,operational implications and financial benefits. [3] Pascale Strubel, A cost-effective way to upgrade urban power networks whileprotecting the environment.[4] High-Temperature Superconducting Wind Turbine Generators Wenping CaoNewcastle University upon Tyne United Kingdom [5] Wikipedia- what is the difference between superconductor and otherconvectional conductor.[6] B. R. Oswald, Technical and Economical Benefits of Superconducting FaultCurrent Limiters in Power Systems [7] Dr.G Schnyder, Application of high temperature superconductor in powersystem