Les travaux effectués pendant la thèse ont principalement porté sur la modélisation et le calcul du comportement haute-fréquence (HF) des câbles électriques. Ces phénomènes physiques mis en jeu combinent les effets capacitifs et inductifs ainsi que les effets de peau et de proximité. Pour prendre en compte de ces comportements, nous utilisons une approche basée sur des circuits équivalents à base aux paramètres linéiques qui varient en fonction de la fréquence. La détermination des éléments du schéma équivalent a été effectuée en résolvant des problèmes d'électrostatique et de magnétoharmonique en utilisant la méthode des éléments finis. Ensuite, nous avons travaillé sur la méthode des lignes de transport (TLM) associée à une approche modale pour déterminer les fréquences de résonance du système en prenant en compte les interconnexions aux extrémités du câble. Nous avons mis en œuvre la méthode ci-dessus pour plusieurs types de câble électrique : bifilaire blindé, blindé de 4 conducteurs, AC triphasée et enfin HVDC. Le comportement HF de ces câbles a été étudié en utilisant l'approche développé. / The work during the thesis focused on the modeling and calculation of high frequency (HF) behavior in the power cables. These physical phenomena involved combining capacitive and inductive as well as the effects of skin and proximity effects. To account for this behavior, we use an approach based on equivalent circuits based on linear parameters that vary depending on the frequency approach. The determination of the equivalent circuit elements was performed by solving electrostatic problems and magnetoharmonic using the finite element method. Then we worked on the Transmission Lines Method (TLM) associated with a modal approach to determine the resonance frequencies of the system taking into account the interconnections to the ends of cable. We have implemented the above method for several types of electric cable: shielded wire, shielded 4 wires, three phases AC and finally the HVDC cable. The HF behavior of these cables has been studied using the developed approach.

The subject of this thesis is to become familiar with the different parameters describing the lines, and the possibility of modeling data and power models. The thesis also outlined the difference in the mechanical structure of different types of cables. The practical part focuses only on the power cables and measure their basic parameters. Then is created computer model which describes the behavior of cable lines at higher frequencies than are primarily intended. The final section is an experimental network created by the PLC for remote reading of electricity meters, and it measured different transmission properties.

I samband med att mellanspänningsnätet kablifieras ökar också kraven vad gäller fellokalisering. För att hålla avbrottstiderna i nätet korta är effektiv felsökning erforderlig. Detta arbete syftar till att kartlägga och redogöra för begränsande faktorer som finns vid fellokalisering med fokus på pulsekometoden. Uppdraget utförs tillsammans med Vattenfall Eldistribution AB. Det har uppdagats problem gällande fellokalisering på mellanspänningskablar med pulsekometoden. Ett flertal faktorer bidrar till denna problematik. Resultatet från studien visar att kabelkonstruktionen är en betydande del i det som begränsar pulsekometodens användningsområden och funktionalitet. Rapporten redogör för grundläggande information kring konstruktion och typer av mellanspänningskablar. Kartläggningen uppvisar hur vattenträd påverkar en kabel negativt. Allmänt redogörs för vad som orsakar vattenträd samt vilka avhjälpande åtgärder som vidtas; trippelextrudering samt mantel- och isolationsprovning. Vidare beskrivs olika feltyper, kabeltyper, kabelgenerationer samt instrument- och metodtyper som alla är påverkande faktorer vid fellokalisering. Dokumentering är i högsta grad väsentligt för en lyckad felsökningsprocedur, vilket klarläggs i rapporten. Utöver dokumentation redogörs för hur kabelns kondition kan påverka felsökningsresultatet. Ett antal mätmetoder och mätinstrument finns till förfogande vid felsökning och provning. Alla har sina egna för- respektive nackdelar. De har även tillhörande användningsområden. Pulsekometerns grundfunktion studeras och förklaras. De övriga mätmetoderna, som används vid fellokalisering och provning, redogörs för endast generellt / As the medium voltage network cables in Sweden is buried down in the earth, the demand of fault localization expertise increases. To keep downtimes in the network short, the importance of effective fault localization is necessary. This work is aimed to map and visualize limiting factors within fault localization with focus on the TDR - Time Domain Reflectometry. This work is a collaboration with Vattenfall Eldistribution AB. Problems with fault localization on medium voltage cables with the TDR have been detected. A multiple factors are contributing to this problem. The results of this study show that the cable construction is a significant part in which extent the TDR can be used. The report are also accounting for basic information about construction and types. The mapping also illustrates water treeing and how it affects cables in a negative way. Visualization of what causes water treeing and several actions such as triple extrusion, jacket testing and insulation testing is included in the essay. Further information about fault types, cable types, cable generations, instrument types and method types is given. All of them are affecting factors within the area of fault localization. Documentation is highly important for a successful fault localization procedure, which is clarified in the report. Besides documentation the cable condition and the influence on it affecting the result of fault localization is stated. A number of measuring methods and instruments are available to use when fault localization and testing are occurring. Every instrument has their own advantages and disadvantages. They also have their own respective area of usage. The basic principle of TDR is studied and explained accordingly. The other measuring methods, which are used in fault localization and testing, are shown more generally

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Distinct matters related to power quality challenges represent areas of growing interest for the electric engineering community. By considering the subject of power supply with quality and reliability, the continuity of the supply appears as a very important task to be fulfilled. As a matter of fact, the occurrence of failures in components and installations, in special those related to the misoperation of power cables, emerges as a relevant point to be tackled. Within this context arises the insulation degradation due to the known water treeing phenomenon. This effect has been reported as a cause for precocious aging of insolated cables and subsequent impacts upon the dielectric material. Focusing this subject, this thesis aims at presenting a methodology for estimating the actual operational conditions of a given insolated cable by the loss current analysis. The technique here employed is based upon time domain representation and uses the Fourier decomposition for identification of the harmonic contribution of the currents involved from which the methodology provides means to establishing insulation state indicators so as to forecast information about the cable life expectance conditions. / As questões relacionadas com a qualidade de energia elétrica representam, efetivamente, desafios crescentes para o setor de engenharia elétrica. No que tange ao fornecimento de energia com qualidade e confiabilidade, um dos problemas consiste na descontinuidade não programada de suprimento devido à ocorrência de falhas em componentes diversos da instalação, particularmente aqueles relativos a defeitos na isolação nos cabos de potência, responsáveis por parcela significativa das paradas intempestivas de consumidores. Uma das principais causas da degradação da isolação de cabos de potência é o fenômeno conhecido por arborescência que provoca o envelhecimento precoce dos cabos elétricos, podendo ocasionar o rompimento do material dielétrico. Diversos estudos e métodos diagnósticos vêm sendo desenvolvidos para a detecção dessas arborescências objetivando informações sobre o nível de degradação da camada isolante, com vistas à manutenção preventiva e acompanhamento da sua vida útil, predizendo as condições operacionais da isolação dos cabos elétricos. É nesse contexto que se insere a presente tese, a qual está direcionada para o desenvolvimento de uma metodologia para identificação do estado operacional da camada isolante, com base na análise da corrente de fuga. A técnica de modelagem empregada fundamenta-se no domínio do tempo e utiliza a decomposição em séries de FOURIER para identificação da contribuição harmônica dos sinais envolvidos no estudo, a partir dos quais são determinados indicadores de estado que são utilizados para o estabelecimento de diagnósticos da severidade da degradação. / Doutor em Ciências

Efficient design of high-voltage power cables is important to achieve an economical delivery of electric power from wind farms and power plants over the very long distances as well as the overseas electric power. The main focus of this thesis is the investigation of electromagnetic losses in components of high-voltage power cables. The objective of the ongoing research is to develop the theory and optimization techniques as tools to make material choices and geometry designs to minimize the high-frequency attenuation and dispersion for HVDC power cables and the power losses associated with HVAC cables. Physical limitations, dispersion relationships and the application of sum rules as well as convex optimization will be investigated to obtain adequate physical insight and a priori modeling information for these problems. For HVAC power cables, the objectives are addressed by performing measurements and estimation of complex valued permeability of cable armour steel in Papers I and II. Efficient analytical solutions for the electromagnetic field generated by helical structures with applications for HVAC power cables have been obtained in Paper III. For HVDC power cables, estimation of insulation characteristics from dielectric spectroscopy data using Herglotz functions, convex optimization and B-splines, has been investigated in Papers V and VI. The unique solution requirements in waveguide problems have been reviewed in Paper IV.

D’ençà que el polietilè reticulat (XLPE) es va començar a utilitzar com aïllament elèctric per cables de subministrament elèctric, s’han destinat molts esforços a l’estudi de les propietats dielèctriques del polietilè i l’efecte que la càrrega d’espai té sobre el seu comportament. En aquest sentit, les corrents de despolarització estimulades tèrmicament (TSDC) s’han utilitzat extensament per estudiar les relaxacions de càrrega d’espai. Aquesta tècnica ha demostrat tenir prou resolució per distingir diferències en aïllaments de XLPE amb composicions o processos de fabricació diferents. En aquesta tesi, els mecanismes de conducció dels aïllaments XLPE de cables de mitjana tensió (MV) han estat estudiats per TSDC i diverses tècniques complementàries, com l’anàlisi dinàmica elèctrica (DEA), les corrents d’absorció/resorció (ARC), el pols electroacústic (PEA) i les corrents de despolarització isotèrmiques (IDC). Altres tècniques, com l’espectroscòpia d’infrarojos (FTIR) o la difracció de raigs X, han estat també utilitzades per caracteritzar el material. S’han obtingut espectres TSDC per diferents mostres de cable, les quals en condicions de servei treballen en un rang de tensió AC de 12 a 20kV i a temperatures al voltant dels 90ºC. D’altra banda, s’han realitzat mesures de la conductivitat per ARC i DEA en mostres de cable, en cilindres de XLPE i en films. Les mesures s’han dut a terme a temperatures pertanyents al rang de fusió del XLPE (50–110ºC), en mostres sotmeses a aquestes temperatures durant diferents períodes de temps. Els resultats mostren diferències importants entre el comportament de les propietats conductives de les mostres de cable amb pantalles semiconductores (SC) i sense (cilindres de XLPE). El comportament observat ha estat explicat mitjançant la coexistència de dos mecanismes de conducció. La difusió d’impureses des de les pantalles SC determina el comportament d’una d’aquestes contribucions a mig i llarg termini. Els resultats obtinguts per FTIR són consistents amb aquest model. Respecte la microestructura, tant les mesures DSC com la difracció per raigs X mostren que existeixen processos de recristal•lització quan les mostres són sotmeses a temperatures ubicades dins del rang de fusió. Els electrets formats mitjançant el mètode de la polarització per finestres (WP) mostren una descàrrega TSDC amb un ample pic heteropolar en el rang de fusió, amb el màxim al voltant dels 105ºC. En treballs previs, aquest pic es va associar a la fusió de la fracció cristal•lina. Tanmateix, en lloc de decréixer quan la temperatura de polarització augmenta, el pic presenta una temperatura de polarització òptima al voltant de 90-95ºC. Aquest comportament ha estat explicat tenint en compte els processos de recristal•lització que es produeixen quan el material es polaritza isotèrmicament. Durant la recristal•lització, una nova fracció cristal•lina creix en un estat polaritzat degut el camp aplicat, i origina una corrent de despolarització quan es fon durant la mesura TSDC. Amb l’objectiu de determinar l’origen d’altres pics que apareixen en l’espectre TSDC del XLPE, s’han emprat les IDC com a tècnica complementària. Les corrents IDC obtingudes de mostres no tractades es poden representar com la combinació de dues contribucions diferenciades: un terme que és una funció potencial del temps i un d’exponencial. La segona relaxació es correspon amb un pic TSDC que apareix a 95ºC. D’aquesta manera s’ha pogut determinar l’origen dipolar del pic. Finalment, mitjançant la tècnica PEA s’ha obtingut la distribució de la càrrega d’espai en mostres polaritzades que havien estat sotmeses a diferents tractaments tèrmics. S’ha observat un comportament transitori tant per PEA com per TSDC. Tanmateix no s’ha pogut establir cap relació directa entre les descàrregues TSDC i mesures PEA. En conseqüència, s’ha proposat una explicació per les corbes TSDC que considera mecanismes que no són detectables en els perfils de càrrega obtinguts per PEA / Since cross-linked polyethylene (XLPE) started to be used as electrical insulation for power cables, much research has been focused on polyethylene dielectric properties and the effect of the space charge on its behavior. In this sense, thermally stimulated depolarization currents (TSDC) have been widely used to study space charge relaxation. This technique has proved to have enough resolution to determine differences in charge trapping properties among XLPE insulations with different composition and manufacturing processes. In this thesis work, the conduction mechanisms of medium voltage (MV) cable XLPE insulation have been studied by TSDC and several complementary techniques, such as dynamic electrical analysis (DEA), absorption/resorption currents (ARC), pulsed electroacoustic (PEA) and isothermal depolarization currents (IDC). Other techniques, like Fourier transform infrared (FTIR) spectroscopy or X-ray diffractometry, have been used to characterize the material. TSDC spectra have been obtained for different cable samples, which in service conditions work under AC voltages ranging from 12 to 20kV and at temperatures around 90ºC. On the other hand, conductivity measurements by ARC and DEA have been performed in cable samples and in XLPE cylinders, as well as XLPE films. Measurements have been carried out at temperatures within the melting temperature range of XLPE (50–110ºC) on samples annealed at such temperatures during several annealing times. Results show significant differences in the behavior of the conductive properties of XLPE cable samples with semiconducting (SC) screens and without them (XLPE cylinders). The observed behavior has been explained by the coexistence of two conduction mechanisms. Diffusion of impurities from SC screens determines the medium and long-term behavior of one of these contributions and, hence, of cable conductivity. FTIR results are consistent with this model. With respect to microstructure, DSC and X-ray diffractometry results show that recrystallization processes exist when samples are annealed in the melting range of temperatures. Electrets formed by means of the windowing polarization method (WP) showed a TSDC discharge with a wide heteropolar peak in the melting temperature range, and with the maximum at about 105ºC. This peak was associated with the melting of the crystalline fraction in previous works. However, in spite of decreasing with the temperature of polarization, an optimal polarization temperature around 90–95ºC is found. This behavior has been explained by taking into account recrystallization processes when the insulation is isothermally polarized. During recrystallization, the new crystalline fraction grows in a polarized state due to the applied electric field, and it causes the depolarization current when it melts during the TSDC measurement. Results obtained from different experiments are consistent with this assumption. With the aim to find out the origin of other TSDC peaks present in the spectrum of XLPE cable samples, IDC has been used as complementary technique. IDC currents obtained from as-received cable samples at temperatures close to service conditions can be considered as the combination of two different contributions: a power law current and a stretched exponential contribution. The last relaxation process has been successfully associated with with a TSDC peak found at 95ºC. By this way the dipolar origin of the peak has been determined. Finally, PEA measurements have provided the space charge distribution profiles of polarized samples with different annealings. A transient behavior has been observed in both PEA and TSDC measurements. However, no straightforward relation between TSDC discharges and space charge detected by PEA can be established. Therefore, an explanation for TSDC curves has been proposed, which considers mechanisms that are not noticeable in charge profiles obtained by PEA.

Examensarbete utfördes hos konsultföretaget WSP Group- Stockholm med syftet att identifiera och hitta förläggningsmetoder som underlättar förläggning av kablar idag och i framtiden. Examensarbetet fokuserar bara på regionnät och lokalnät i storstäder men med inslag av stamnät. Detta examensarbete bygger på informationssamling från standarder EBR KJ41:15 kabelförläggning max 145 kV, SS-EN 424 14 37 och Stockholm stad tekniska handbok. Som komplettering till standarderna användes handböcker från olika företag samt gamla examensarbeten. Svar på frågeställningar är baserad på intervjuer med olika aktörer inom branschen så som nätägare, konsuler, och entreprenörer. Genom intervjuerna kom man fram till att rör används i första hand inte för att skydda kablar utan för att kunna passera genom en väg, rör leder till att värmeavledningsförmågan försämras vilket innebär att temperaturen på kabeln stiger och i värsta fall förkortar livslängden på kabeln. Att gå upp i ledararea för kablar är inte möjligt eftersom det är trångt i marken och det krävs mycket plats. Bentonitfyllning är ingen bra metod eftersom det inte finns data på vad som kan hända med bentoniten efter 5 år eller 20 år, och det är svårt att komma åt kablarna och reparera de eftersom bentoniten måste spolas ur. Om bentoniten stelnar kan det bli svårt att komma åt kabeln. Det visade sig att grävning är den enda metoden som används i storstäder eftersom andra metoder kan orsaka skador på befintliga ledningar som ligger i marken. De vanligaste kabelfelen är gräv skador på kablar, det är väldigt lätt att man kommer åt markkablarna vid schaktarbetet. För att kunna bygga ut nätet i framtiden kan man förlägga kablar med större ledningar för att täcka framtida behovet. I de områden där man vet att nätet inte behöver förstärkas kan man förlägga i rör för att underlätta underhållsarbetet i framtiden. Staden måste vara mer tydliga med sina planeringar och säga till att hålla sig till det. Staden måste också ansvara för sin mark och inte låta någon annan ta hand om nätet. Ledningsägarna måste bli bättre på att samförlägga och agera snabbt med att komma ut med detaljer på vart man vill samförlägga för att slippa schakta och störa markägaren flera gånger. Det kommer bli ännu trängre i marken i framtiden och det låter som att man kommer behöva bygga tunnlar. Tunnlar är en dyr infrastruktur och ifall flera aktörer väljer att samförlägga kan kostnaderna för tunnelbyggnation fördelas mellan olika aktörer. OPI kanalisation är också en annan typ av lösning och det är väldigt bra om flera aktörer också kan samförlägga. Idag är man ganska dålig på att samförlägga och det är något som man måste bli bättre på. / The thesis work was carried out at the consulting company WSP Group- Stockholm, with the purpose of identifying and finding installation methods that facilitate the placement of cables today and in the future. The thesis focuses only on regional and local grids but with elements of main grids in major cities. This degree project is based on information gathering from standards EBR KJ41: 15 cabling max 145 kV, SS-EN 424 14 37 and Stockholm City Technical Manual and the differences between them. As a supplement to the standards, different manuals were used by different companies and also past thesis work. Answers to main question and subquery are based on interviews with various actors in the industry such as grid owners, consultants, and entrepreneurs.  The interviews revealed that pipes are used primarily not to protect cables, but to pass through a road. Pipes Installation lead to deterioration of heat dissipation in cables, which means that the temperature of the cable rises and, in the worst case, shortens the life of cable. Walking up the cable wiring area is not possible because it is crowded in the ground and requires a lot of space. Bentonite filling is not a good method because there is no data on what can happen with the bentonite after 5 years or 20 years. It would be difficult to access the cables and repair them because the bentonite must be flushed out. If the bentonite is stiff, it can be difficult to access the cable. It turned out that excavation is the only method used in metropolitan areas because other methods can cause damage to existing wires lying in the ground. The most common cable damages are digging in cables, it is very easy to access the ground cables at the installation work. In order to expand the network in the future, cables with larger wires can be placed to cover future needs. In areas where you know that the network does not need to be strengthened, pipes can be placed to facilitate maintenance work in the future. The city needs to be clear about where the future constructions will be and develop a plan and stick to it. The city must also be responsible for its land and not let anyone else take care of the network. Management owners need to be better at co-ordinating and acting quickly to come up with details on where to co-ordinate to avoid bottleneck and disturbing landowners several times. It seems that tunnels will be a way to go in the future. Tunnels is an expensive infrastructure and if several actors choose to collaborate, the costs of tunnel construction can be divided between different actors. OPI channelization is also another type of solution and it is very good if several players can also collaborate / <p>Godkänd</p>

This master’s thesis is concerned with the proposal of new locality electrification. There are 59 detached houses. The thesis is divided into theoretical part and computational part. In the theoretical part, there are all documents necessary for the successful proposal of the electrification. In the computational part is drafted distribution substation, high voltage power cable, proposal of low voltage power cables and protection. Each part is made for two versions (for the degree of electrification A and for the degree of electrification C) and recorded in cadastral maps. The proposal of distribution substation and high voltage power cable is made by traditional method - all calculations are processed by the designer. Low-voltage power cables and protection are implemented in a computer program Sichr (version 11.01) OEZ company.

Detta examensarbete utfördes vid Bodens Energi Nät AB under våren 2017 och behandlar mätmetoder och olika tester som kan utföras på markförlagd kabel för kontroll av tillståndet på exempelvis isolation, mantel och skarvar. Bakgrunden till arbetet är att man inom Bodens Energi Nät har ett flertal kilometer kabel på mellanspänningsnivå 20 kV. En stor del av kablarna är isolerade med tvärbunden polyeten, PEX och härstammar från 1970 och 1980-talet. Dessa kablar har i efterhand visat sig ha problem med vattenträd, vilket kan beskrivas som trädliknande strukturer som uppstår i en kabels isolation på grund av fukt och orenheter när dessa blir utsatta för kraftigare elektriska fält. Problem med vattenträd i kablar leder efter en tid, ofrånkomligen till genomslag i isolationen med påföljande jordfel.  Syftet med denna rapport är att undersöka och kartlägga olika tillståndsbedömningsmetoder för kraftkabel avsedd för 12/24 kV-nät. Rapporten avser att vara en metodbeskrivning för de vanligaste diagnostiska mätmetoder samt redogör för dess för- och nackdelar. Följande frågeställningar ämnas besvaras: Vilka metoder finns tillgängliga för tillståndsbedömning av mellanspänningskabel och vilka egenskaper är mätbara? Vad har respektive mätmetod för svagheter och styrkor samt vilka begränsningar finns det? Finns det möjlighet att utföra mätningar på en kabel i drift eller måste den tilltänkta kabelsträckan frånskiljas den övriga anläggningen?Om mätningar kan utföras på en kabel i drift, vilka metoder gäller detta? Rapporten bygger till största del på en litteraturstudie där mycket av informationen är hämtad ifrån standarder, handböcker och guider. Rapporten behandlar dels allmän information om kraftkablar samt PEX-kabelns konstruktion vilket bör kännas till för att kunna tillgodogöra sig informationen på bästa sätt. Vidare avhandlas åldringsmekanismer för PEX-isolerad kabel. Metoderna som presenteras i rapporten omfattar bland annat; mantelprovning, hållprov med olika typer av spänning, mätning av den dielektriska förlustfaktorn tan delta samt mätning av partiella urladdningar, PD. I kapitel 5 presenteras mätresultat från ett antal olika tan delta-mätningar samt en mätning av partiella urladdningar, vidare ges en kortare förklaring till mätresultaten. Vid mätning av de dielektriska förlusterna fås information om isolationens totala skick. Mätning av partiella urladdningar (även kallat glimning) ger information om var eventuella ojämnheter och håligheter finns. Det är dock viktigt att komma ihåg att de metoder som finns måste anpassas till den kabel som avses mätas eftersom det inte går att identifiera alla typer av defekter och fel med hjälp av endast en metod. Metoderna bör användas som diagnostiska hjälpmedel som i sin tur ger fingervisningar om kabelanläggningens totala tillstånd. De är därmed inte att betrakta som en definitiv bekräftelse avseende funktionsdugligheten för kabeln. / The work in this bachelor’s thesis was conducted at Bodens Energi Nät AB during the spring of 2017. The report describes common methods available for testing and diagnostic measurements of electric power cables. Bodens Energi Nät manages a medium voltage power grid which consists of around 700 kilometers of power lines and about 200 kilometers of cables. A large part of these cables have an insulating layer consisting of cross-linked polyethylene (XLPE) and originates from the 1970s and the 1980s. These particular XLPE cables have a higher than normal tendency to develop problems with water trees. Water trees can be described as tree-shaped structures forming inside the insulating layer of the cable in the presence of an electrical field and water. Issues with water trees leads to local degradation of the dielectric material in the cable and usually ends with a phase-to-ground fault. The purpose of this thesis is to examine and describe different methods for diagnostic measurements of medium voltage cables. Through the use of a literature study the following questions will be answered: Which methods are available for diagnostic measurements and what properties can be measured? What are the strengths and weaknesses for each of these methods? Can measurements be performed on cables on-line or is it required to disconnect the cables from the grid before any measurements can be performed?In the case of on-line testing, which methods does this apply to?  The overall disposition of this thesis starts with a general description of power cables including XLPE cables, as well as aging mechanisms in extruded cables. Subsequent chapters describes testing methods such as cable sheath testing, hipot testing using different types of voltages, measurements of the dielectric dissipation factor tan , as well as partial discharge testing.  Chapter 5 discloses the results from some different tan  measurements including a partial discharge measurement. A short description and explanation is included with every figure.  Measuring the dielectric dissipation factor yields information about the total condition of the insulation. Partial discharge offers information regarding the location of irregularities, cavities and impurities within the insulation. It is important to have in mind that each of these methods on its own will not be able to identify all types of defects. Therefore it may be required to carry out several measurements using different types of methods in order to get a general idea of the condition of the cable. Methods for cable diagnostic measurements should be seen as a tool to get an estimate about the total condition of a power cable and is not considered a fail safe way to determine the operational ability.

Une analyse critique de la modélisation des échanges thermiques des câbles d’énergie en galerie est réalisée, avec l’étude de facteurs d’influences propres aux modes de pose des câbles dans ces ouvrages. Les câbles, de plusieurs kilomètres, chauffent du fait du courant transmis dans leurs âmes. Ils sont alors refroidis par une convection forcée turbulente, dans l’axe des câbles, et échangent par rayonnement avec les parois. Pour étudier ce refroidissement, un banc d’essais expérimental a été conçu, en similitude de Reynolds, modélisant différents câbles soumis à un écoulement turbulent développé. Les résultats sont comparés et étayés par des simulations numériques 3D, développées sous l’outil OpenFOAM. Les études réalisées ont permis de mettre en évidence la mésestimation importante de l’échange convectif par la norme existante. Celle-ci propose un refroidissement qui se compose en réalité pour un tiers de l’effet de supports maintenant les câbles et d’un autre tiers d’un écoulement encore en début d’établissement. Le dernier tiers étant le refroidissement effectif des câbles. L’impact des groupements des câbles est aussi étudié, avec un résultat étonnant où un groupe de deux câbles en nappe est trouvé mieux refroidis qu’un seul, lorsque ceux-ci sont placés en proche paroi de la galerie. A l’issue des travaux, une unique loi de refroidissement conservative est proposée, permettant de modéliser tous les cas traités. Cette loi a un impact important sur l’intensité maximale admissible des câbles, qui est dégradée de 5% à 9% par rapport à précédemment pour un cas idéalisé. / A critical analysis of the thermal rating of power cables in tunnels is carried out, with the study of factors of influence specific to cable laying constrains. The heat generation in the cables, due to the transiting current, is dissipated by an axial turbulent forced convection and by radiation with the tunnel walls. To characterize this cooling, an experimental mock-up tunnel has been designed, modelling various cables in a fully-developed turbulent flow. The results are compared and bolstered by 3D numerical simulations, developed under the OpenFOAM code. The studies have highlighted an important underestimation of the convective exchange by the existing standard. Their cooling law is actually a sum of the effects of racks supporting the cables, for a third, and the effect of a flow still underdeveloped for another third. The last third being the actual cooling of the cables. The impact of groups configurations is also studied, with an astonishing result for groups of two cables, which are better cooled than a single cable case, when installed close to a wall. Following the analysis, a single conservative cooling law is proposed to model all studied cases. This law has a significant impact on the permissible current in the cables, which is downgraded from 5% to 9% from previous ratings.