Over the past decade, underground power distribution has become increasingly popular due to its reliability, safety, aesthetic characteristics, as well as the ever increasing focus on the environmental impacts of the various stages of power generation and distribution. With the technological advances in this area, the process of running these cables have become more economical and efficient. This thesis explores the practice of grouping multiple three phase cables in a common conduit, using the duct bank process, and analyzes the thermal and ampacity consequences on the individual lines. This analysis is done in an effort to better define and understand the various limitations of the practice and explore future possibilities in its expansion.

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abstract: Underground transmission cables in power systems are less likely to experience electrical faults, however, resulting outage times are much greater in the event that a failure does occur. Unlike overhead lines, underground cables are not self-healing from flashover events. The faulted section must be located and repaired before the line can be put back into service. Since this will often require excavation of the underground duct bank, the procedure to repair the faulted section is both costly and time consuming. These added complications are the prime motivators for developing accurate and reliable ratings for underground cable circuits. This work will review the methods by which power ratings, or ampacity, for underground cables are determined and then evaluate those ratings by making comparison with measured data taken from an underground 69 kV cable, which is part of the Salt River Project (SRP) power subtransmission system. The process of acquiring, installing, and commissioning the temperature monitoring system is covered in detail as well. The collected data are also used to evaluate typical assumptions made when determining underground cable ratings such as cable hot-spot location and ambient temperatures. Analysis results show that the commonly made assumption that the deepest portion of an underground power cable installation will be the hot-spot location does not always hold true. It is shown that distributed cable temperature measurements can be used to locate the proper line segment to be used for cable ampacity calculations. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2015

According to International Electrotechnical Commission’s standard document IEC-60287 the current carrying capabilities of power cables can be mathematically modelled. Current rating of power cables can hence be done without having to perform expensive and timely experiments. This allows different techniques in power cable utilizing and placement to be compared to one another. In this master thesis two different techniques for placement of power cables are investigated using IEC-60287. A conventional technique where the electric power cable is placed in a cable trench is compared to the method where the power cable is placed in a protective plastic duct. Comparisons have been made in the areas: current carrying capacity, economy and technical simplifications. Based on the analysis in this report results show that the theoretical current carrying capacity (ampacity) of the power cable placed in a plastic duct is sufficient for usage under given circumstances and that the method allows greater flexibility regarding the interface between contractors. Conclusions from this master thesis should be used only based on circumstances very similar to the set-up described in this report. Current carrying capabilities of power cables diverges depending on cable model, surrounding media, protective plastics and/or metals and many more properties of the system. Each system demands an investigation of it’s own, but systems containing power cables buried in plastic ducts can with support from this report be closely described.

M. Tech. Engineering: Electrical. / Discussing the developing an entirely software based synchrophasor platform for transient stability analysis of a multi-machine system by exploiting the possibility of distributing a precise time reference by means of communication networks and an open source software-only Precision Time Protocol (PTP) to synchronise PMUs and evaluates the precision of this synchronisation in the event of faults in a power system.

There is an ever increasing demand of electricity and to meet this demand, installation of new transmission and distribution lines is required. This task requires a significant investment and consent from the respective authorities. An alternative is to utilize maximum capability of the existing lines. Static line ratings are based on a conservative estimate, which means that on most occasions, the actual capacity of lines is much higher than the static line ratings. In order to provide a solution to this problem, this thesis introduces an approach that has been developed to utilize real time weather conditions, conductor sag data and the actual line loading of the conductor from PMU to provide dynamic line ratings for active distribution networks. The application has been developed in LabVIEW environment which provides a user friendly front panel where real-time ampacity can be seen as a waveform while being compared to the actual line loading.  The developed application has been tested on the reference grid created for IDE4L project. The ampacity calculation method introduced here makes use of real-time data available through a real-time simulator in SmarTS lab at KTH, Sweden. / Det är ett ökande behov av elektricitet och för att möta detta behövet, installation av nya transmission och distributionsledningar behövs. Denna utbyggnad kräver ett stort engagemang och förståelse från ansvariga grupper. Ett alternativ är att utnyttja max-kapaciteten på redan befintliga ledningar. Installerade ledningar har räknats på ett konservativt sätt, vilket innebär att det vid vissa tillfällen går att öka belastingen på på dessa. För att ge en lösning på detta problem, introducerar den här avhandlingen en metod för att använda realtids-väderdata, tabeller för ledningarnas utvidgning och realtids-belastningsdata från PMU för att framställa dynamisk data för aktiva distributions-nätverk. Applikationen har utvecklas i LabVIEW-miljön som har ett användarvänligt GUI, där “Real-time ampacity” kan ses som en vågform medans den jämförs mot den faktiska belastningen på ledningen.  Den utvecklade appliktionen har testats på referens-miljön som skapts för IDE4L projektet. “Ampacity calculation metoden” som introduceras här använder sig av realtidsdata som görs tillgänglig igenom en realtids-simulator i SmarTSlab på Kungliga Tekniska Högskolan i Sverige.

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Detta arbete undersöker temperaturdynamiken och sluttemperaturen hos ledare iinstallationskablar för olika fall av belastningsström. En laborativ model och entidsstegande numerisk modell har skapats och jämförts. Resultaten jämförs med denmärkström som ges i installationsstandarder, och även med de överlastnivåer somkan tolereras av säkringar och strömbrytare enlig Europeiska standarder.Exempel på användningsområden för studiens resultat är kabelklassificeringar medtillfälliga laster, och potentiell överlast på grund av tung belastning kombineratmed extra matningar till en krets (t.ex. inkopplad solkraft). De studerade kablarnavar fyllda och ofyllda 3-ledarkablar (varav 2 belastade) med PEX-isolering, allamed 1,5 mm2 kopparledare (EQLQ 3G 1,5 mm2). De testades fritt i luft och i ensektion av värmeisolerad vägg. Strömmar applicerades från en styrbar likströmskälla.Ledarens temperatur mättes genom att logga spänningsfallet över en cirka 10 cmlång ledarsektion, med tanke på resistansens temperaturkoefficient. Denna metodverifierades genom tester i ett värmeskåp.Resultaten visade att ledarna maximalt nådde 92 % av den tillåtna drifttemperaturen(90 ◦C) vid 150 % belastning av typisk säkringsstorlek. Kombinerat med extramatningar nådde den maximala temperaturen 118 % av drifttemperaturen vid 170 %belastning av typisk säkringsstorlek. Resultaten visade också en temperaturskillnadmellan horisontella och vertikala förläggningar, som varierade från 3-10 ◦C högre idet vertikala fallet, beroende på belastning och kabel. / This work examines the temperature dynamics and final temperature of conductorsin electrical installation cables, for various cases of load current. A laboratory modeland a time-stepping numerical model have been made and compared. Results arecompared with the ampacity given in installation standards, and also with theoverload levels that could be sustained by fuses and circuit breakers, followingEuropean standards.Examples of use-cases for the study’s results are cable ratings with intermittentloads, and potential overload due to heavy load combined with extra infeeds intoa circuit (e.g. plug-in solar power). The studied cables were filled and non filled 3-conductor (of which 2 loaded) PEX insulated installation cables, all with 1.5 mm2copper conductors (EQLQ 3G 1.5mm2). They were tested in open air and in a sectionof insulated cavity wall. Currents were applied from a controlled dc current source.The conductor temperature was measured by logging the voltage drop across a 10 cmlength of conductor, bearing in mind the temperature coefficient of resistance. Thismethod was verified by tests in a heating chamber.Results showed that conductors reached a maximum of 92 % of the permissibleoperating temperature (90 ◦C) at 150 % load of typical fuse-size. Combined withextra infeeds the maximum temperature reached 118 % of operating temperatureat 170 % load of typical fuse-size. The results also showed a temperature differencebetween horizontal and vertical orientations, varying from 3-10 ◦C higher in thevertical scenario, depending on load and cable

Dans le contexte de la montée des préoccupations écologiques, le développement de véhicules de transports routiers s’oriente vers le développement de véhicules moins polluants à entraînement électrique comme les Véhicules Électriques Hybrides (VEHs) et les Véhicules tout Électriques (VEs). Avec l’augmentation des puissances requises et la réduction de l’espace disponible, la gestion thermique devient une préoccupation de plus en plus importante lors du développement des composants embarqués comme les moteurs/générateurs électriques, onduleurs, batteries et faisceaux électriques. Parmi eux, le faisceau électrique de puissance qui est typiquement composé de câbles électriques, de connecteurs et de boîtes de distribution de puissance ne peut être conçu de manière appropriée qu’à la suite d’une analyse thermique, électrique, chimique et mécanique approfondie.Cette thèse est écrite pour contribuer à l’optimisation de la conception électrothermique de faisceaux de câbles par des simulations afin de réduire la quantité de tests expérimentaux nécessaires pour leur développement. Des modèles théoriques pour la prédiction du comportement électrique et thermique de câbles électriques et des faisceaux de câbles sont passés en revue et adaptés aux exigences automobiles. La validation est accomplie en comparant les résultats de simulation avec ceux d’analyses élément finie (FEA) et de données de mesure. Une partie majeure de cette thèse aborde la simulation thermique de câbles électriques de longueur infinie suspendus dans l’air, prenant en compte les dépendances en température des résistances de conducteurs et la non-linéarité du coefficient de transfert thermique total à la surface du câble. L’influence des courants de blindage et de courants arbitraires dans les conducteurs sur la montée en température des câbles électriques est considérée dans des circuits thermiques équivalents et illustré par des exemples pratiques. / In the context of growing ecological concerns, the development of road transport vehicles moves itself toward the development of less polluting vehicles with electric drives such as Hybrid Electric Vehicles (HEVs) and full Electric Vehicles (EVs). With rising power requirements and reducing available space, thermal management is becoming an increasingly important concern during development of on-board vehicle components such as electric motor(s)/generator(s), power inverter(s), battery pack(s) and cable harnesses. Among them, the cable harness which is typically composed of electrical cables, connectors and power distribution boxes can only be designed properly after a detailed thermal, electrical, chemical and mechanical analysis.This thesis is written to contribute to the optimization of the electro-thermal design of cable harnesses through simulations and reduce the amount of experimental testing needed during their development. Theoretical models for the prediction of the electrical and thermal behavior of electric cables and cable harnesses are reviewed and adapted for automotive requirements. Validation is accomplished by comparing simulation results with Finite Element Analysis (FEA) and measurement data. A major part of this thesis addresses the thermal simulation of electrical cables of infinite length installed in air, taking into account the temperature dependencies of conductor resistances and non-linearity of the total heat transfer coefficient at the cable surface. The influence of shielding currents and arbitrary current loads in the conductors on the temperature rises within electric cables is also considered using thermal ladder networks and illustrated by practical examples. Because shielding currents in vehicles are not only caused by induced currents but also by functional electrical currents generated by low-voltage power sources, new theoretical studies and experimental observations for the estimation of these currents as a function of the vehicle electrical architecture and circuit characteristics are presented. A primary finding reveals that keeping the resistance of grounding connections low compared to that of the shielding connections is an appropriate but expensive means for limiting the transfer of functional currents in the shielding circuits. Finally, a complete and modular model for the prediction of transient temperatures along the length of cable harness sections is developed and validated based on the outcomes of all previous findings.