The thermal behaviour of an IGBT module was investigated, especially with respect to the module being immersed in dielectric oil. An equivalent thermal model was built using thermal transients and network synthesis. The thermal behaviour was further investigated using thermocamera measurements and simple finite element models. Passive pressure testing of electronic components relevant for the test setup was performed. The testing showed no significant influence on the electrical behaviour of the components. An IGBT module without gel covering the chips was switched while immersed in dielectric oil. The switching transients were compared to the case of a normal module switching in air. Only minor differences were found between the switching waveforms from the two cases. A test was performed where water was added to the dielectric oil in order to reduce the breakdown voltage of the oil. No breakdown phenomena were observed for the voltages that were tested. A brief litterature study regarding stray inductance considerations in the test setup was performed.

This thesis studied reliability of power supply in Zambia following two major power blackouts that affected the whole country. The case study focussed on the generation and transmission network owned by Zambia’s biggest utility company Zesco. Three methods of study were selected. The first method looked at the transient stability simulations of Zesco generators when subjected to a large disturbance after a three phase short circuit was applied at three selected buses which are considered critical to the system. The simulations were carried out in SIMPOW. The results show that with fault duration of less than 200 milliseconds, all generators regained synchronism after fault removal. However, extending the fault duration to 200 milliseconds resulted in loss of synchronism in generators at Victoria Falls power station. The second method studied the contingency of some critical components in the Zesco system. The contingency analysis was implemented using software called NETBAS. Study showed that the Zesco system is N-1 stable for contingencies involving transmission lines and transformers. However the system is vulnerable to contingencies involving major power stations such as Kafue gorge and Kariba North bank. The third study proposed modification to the distance protection system to include the effect of zero sequence mutual coupling resulting from parallel circuits following a fault involving earth on a protected line. Adaptive techniques were developed where the settings of the distance relay would change to suit the circuit configuration. This technique resulted in optimal performance of the distance relay under all conditions of parallel line operation. The thesis concludes by making recommendations based on the findings from the studies carried out.

Norway and the EU have in recent years established ambitious goals to increase the share of renewable energy in their consumption. On account of these goals, a large-scale wind power development can be expected in northern Norway and Sweden. This development may be financed both by Norway and by countries with less wind resources in order to meet the energy goals imposed upon them. An increased power surplus is dependent on TSOs' abilities to transmit increased amounts of power through the Nordic grid. A scenario of likely power market conditions in year 2025 is used as a basis. The scenario has a high expectancy of new wind power as well as strong grid investments compared to the level in 2009. This thesis assumes an additional increase in annual renewable power production of 22 TWh, divided into 16 TWh in northern Norway and 6 TWh in northern Sweden. Results show that this amount of new power cannot be implemented without large grid investments. The Energy and Power Flow model is utlized to simulate the Nordic power flow for different levels of grid investments. Two grid solutions are proposed that allow the production increase while maintaining an acceptable state of system operation. The first uses DC transmission from Rana to Oslo in order to control power flow through Norway. An additional AC line from Kobbelv to Ritsem allows import from Sweden to the DC line. The second grid solution uses AC line upgrades throughout Norway ensuring two 420 kV lines from Ofoten to Kristiansand. Due to lower impedances in the Swedish grid, a large amount of the Norwegian production flows into and through Sweden. This solution requires a new line from Kobbelv to Ritsem and Rätan to Borgvik in order to solve resulting Swedish transmission congestion. Both grid solutions require a new DC cable from southern Norway to Germany in order to export most of the new power production. These cables require a number of supporting line upgrades in the region. Power producers schedule according to the new market situation, allowing a very high export during daytime and a low export during night. The increased power production in northern Norway and Sweden replaces other production. A high amount of gas and coal power is replaced in continental Europe. No hydropower, wind power or nuclear power is replaced. The DC and AC grid solutions allow European reductions corresponding to 19,3 % and 16,6 %, respectively, of the expected Norwegian CO2 – emissions in year 2025. The cost of each grid solution is calculated to 22 760 MNOK and 19 310 MNOK. Annual system increases in valued socio-economic benefit outweigh the grid investment costs of each option by 3 300 MNOK and 3 370 MNOK per year of the period of analysis. The total cost of new power production must not exceed these values for such a decision to be socio-economically beneficial. Due to the high increases in calculated socio-economic benefit, a recommendation for further analysis is made.

This thesis presents the laboratory test data on Bisphenol A epoxy insulation.This thesis work deals with electrical, mechanical and thermal analysis of Bisphenol A epoxy resin. The main aim of this thesis work was to examine if dry and wet aging changes the glass transition temperature (Tg) of the epoxies and measure the impact on the complex permittivity under different ageing conditions namely dry and wet. During ageing the samples (epoxy discs and dog bones) were kept in water at 20°C, 45°C and 80°C both in dry and wet conditions for a period of one month. After the samples were removed from ageing they were conditioned in a vacuum oven for one week. The effect of temperature and relative humidity on unaged epoxy i.e. dry characterization was determined by keeping the samples in climate chamber with 15%RH (Relative Humidity) and temperatures 20°C, 45°C and 80°C. The wet characterization was carried out with 90%RH and temperatures 20°C, 45°C and 80°C. The surface of these samples was painted with silver paint (electrodes). Two circular discs were used for dielectric response measurement and 2 rectangular pieces for water sorption measurement. The dielectric response was measured when equilibrium/saturation condition was achieved. The dielectric response was measured in the frequency range from 0.01 Hz to 1000 Hz at 200 volts (peak). The wet characterization showed increases with aging temperature. The dielectric loss was also increasing with the temperature. It can be deduced that the water uptake by the epoxy increases with increase in humidity and temperature. The dry characterization showed and has steady growth with aging temperature. Therefore it can be deduced that characterization done in dry condition didn’t significantly affect the complex permittivity as compared with wet characterization. The glass transition temperature (Tg) of the samples were found using DSC (Differential Scanning Calorimetry) with a heating rate 20°C/min. The Tg was measured in the samples in dry condition before the water absorption process, then in samples after the water absorption process with moisture in the sample, and then in sample after the desorption. The effect of water on the Tg of the epoxy polymer was studied. Tg was increasing with aging temperature, for both dry as well as wet samples. The increase in the value can be mainly attributed to post curing process of the epoxy. The mechanical strength of the epoxy was studied by applying a tensile force to the dog bone shaped samples till breakdown and the stress versus strain curve was detected. This test was also performed on the dry aged sample before water absorption, then in sample which was kept under water at 20°C ,45°C and 80°C for absorption, and in sample which has undergone absorption and desorption at 20°C ,45°C and 80°C. The difference between the stress-strain curves was documented and discussed. The ageing temperature plays a significant role in reducing the value of stress and percentage strain at max. For dry aged epoxy, stress reduces around 14% from 200C to 800C. However for wet aged epoxy samples tensile strength reduces around 25%. For dry aged samples % strain reduces around 0,3 %. and for wet aged samples it reduces around 0,5%.

This master thesis treats the research of a novel “generator with converter” design called “Doubly Fed Permanent Magnet Synchronous Machine”, DF-PMSM, patented by SmartMotor. The thesis includes an introduction to the machine, a state-of-the-art survey, a hydro power case, simulations and a laboratory experiment. The DF-PMSM concept adds an important feature to fixed speed PMSM systems; the reactive power can be regulated. Compared to a direct coupled PMSM the DF-PMSM concept can add voltage control (by controlling the reactive power) in addition to active power control. The concept is based on a 6-phase Permanent Magnet Synchronous Machine where the windings are grouped into two sets of 3-phase, both situated in the stator. These winding sets are named “control” and “power” winding, named after their purpose in the design. The “control winding” is routed through a converter with active-front-end rectifier. It will be used to control the reactive power and the active power from the control winding. The “power winding” will carry most of the generated power, directly coupled and in sync with the voltages of the connected grid. The state-of-the-art survey includes constant speed and variable speed generators utilized in hydro power generation today. It also includes some general info about doubly fed and multiphase machines. The grid regulations for Norway are also investigated to give a pointer to what requirements that the DF-PMSM needs to fulfill to be connected to the grid. The machine simulations are done in LTspice where machine simulation models are developed for this purpose. Simulation of machine startup and changes is load is done. The simulation models are developed as hierarchical sub blocks that can be re used in later simulation cases. The laboratory is done with two machines in back-to-back configuration with industry standard converters. The DF-PMSM is made from a 3-phase permanent magnet machine that is rewired to a 6-phase configuration. The laboratory exercise includes start up, synchronization of the power winding to the grid, machine loading and reactive power compensation by the active front end converter. The DF-PMSM is confirmed working and design considerations are given based experience gained from working with this design. All of this information is included in this report and the further work needed before this machine is constructed and sold is sketched in the conclusion.

Four samples of galvanized steel armour for sub sea power cables are tested with an electric steel tester. The samples exhibit different remanence magnetization and permeability. The effects of permeability on loss in sub sea cables is found to be insignificant. Slight increase of conductor inductance due to increase in permeability of armour wires is observed. Mutual cancellation of inductance between circuits that are twisted opposite to each other, or with respect to one circuit, is confirmed with laboratory tests and measurements on full scale sub sea power cables. The parameters of one cable is calculated using IEC’s analytical approach and found to be inaccurate for conductor resistance. The Calculations places 22% of total cable loss in the armour. Measurements on two sub sea cables and analysis using finite element method contradict the calculated armour loss. Parameters for two sub sea power cables are calculated based on measurements performed on the actual cables. The calculated values are compared with values computed using finite element analysis. Derived physics from laboratory experiments and measurements on the cables is applied in finite element analysis and found to be accurate compared with calculated values from measurements and computed values using Flux 2.5D.

The tendency of connecting the loads to the three phase AC system through power electronic interfaces is increasing with time. These interfaces greatly affect the performance of the power system when properly operated. The injection of reactive power by these interfaces provides the possibility to support the voltage, increase the stability margins and decrease the power losses in the power system. The power electronic loads when tightly regulated consume constant power from the grid and therefore exhibit negative resistance instability behavior. A fast control system with high stability margins is desirable for the converters. This thesis deals with the control of power electronic loads and the stability of the AC distribution system. One of the objectives of the work is to understand the basic control structure of the converters and establish the tuning rules for the PI regulators of the converter controllers. A basic power electronic converter is considered and vector control method is implemented. A mathematical model of the control system for the converter is described and transfer functions are analyzed in frequency domain for different values of grid voltage. The simulations in time domain are performed in PSCAD/EMTDC software. The simulation results validate the results from the frequency domain analysis. The simulation analysis also shows that the stability of the converter in generation mode is higher as compared to when it acts as a load. A larger model of AC distribution system with different shares of loads is investigated for the transient stability. It has been observed through simulations that the injection of reactive power during contingency greatly improve the stability limits of the system. However this increase in the stability margins comes at the cost of an increase in converter current rating. A comparison between the distributed injection by parallel converter and centralized injection through STATCOM confirms the advantages of the distributed injection.

Næringsbygg står for en betydelig andel av energibruken i Norge. Ut fra økonomiske, samfunnsmessige og miljømessige forhold er det i dag et betydelig fokus på å redusere denne energibruken. Denne hovedoppgaven omhandler energisparepotensialer i næringsbygg. Bygget til Adresseavisen ASA på Heimdal utenfor Trondheim er blitt brukt som referansebygg da målinger og undersøkelser ble gjort der. Skal man redusere energibruken bør man også ha opplysninger om hvor energien blir brukt, når den blir brukt, hvor mye og bakgrunnen for forbruket. Det har også vært ønskelig å kartlegge om det er forskjell i energibruken i kontorlandskaper kontra cellekontorer, og hva som eventuelt er bakgrunnen for denne forskjellen. Med utgangspunkt i at energibruken skal være behovsprøvd og at energibruken skal reflektere antall brukere som benytter arealene har det her blitt benyttet tre metoder for å innsamle informasjon om energibruken. 1.Logging av effektuttak på sikringer i underfordelingen 2.Tilstedeværelsesdetektering og lysbruk 3.Spørreskjema Logging av effektuttak ble foretatt på døgn- og ukebasis over ulike gruppesikringer i to forskjellige områder. Det ene området var inndelt i cellekontorer, mens det andre bestod hovedsakelig av åpne kontorlandskap. For registrering av tilstedeværelse og lysbruk i et område ble det laget utstyr som ble testet og utprøvd, for å se om dette kunne gi verdigfull informasjon omkring lysbruken i områder, og for å avdekke eventuelle forskjeller mellom områdene. Et spørreskjema delt ut i slutten av måleperioden til et utvalg ansatte for kartlegging deres holdninger og vaner i forhold til eget energibruk. Målingene som ble foretatt viser at det er en forskjell i hvordan energien ble brukt i de ulike områdene. Cellekontorene hadde et energiforløp som nådde sitt toppunkt midt på dagen, for deretter å reduseres til et lavere og mer stabilt uttak over ettermiddagen, kvelden og natten. I noen tilfeller var energibruken om kvelden og natten lik, før ny arbeidsdag startet og energiuttaket økte igjen. Fra målingene fikk man inntrykk av at belysningen i fellesarealer og korridorer sto på store deler av døgnet. Kontorlandskapene hadde et noe annet forløp. Dette var preget av jevnt høyt uttak over store deler av døgnet, kun avbrutt av korte perioder noen netter der effektuttaket sank vesentlig. Tilstedeværelsesdetekteringen på cellekontorer ga indikasjoner på en brukstid av rommet i underkant av det driftstiden på belysningen var. Differansen mellom disse varierte en del fra kontor til kontor, men det som gikk igjen var at lyset ble slukket da brukerne forlot områdene for dagen. Målingene viste at brukstiden for kontorlandskapene lå opp mot 15 timer i døgnet, mens den på cellekontorene aldri oversteg 7,5 timer i døgnet. Lystiden var også ulik i de to områdene. På cellekontorene lå lystiden stort sett mellom 7 og 8 timer, mens den for kontorlandskap varierte mer, med flere tilfeller der lyset sto på hele døgnet. Spørreskjemaet bekreftet mye av det målingene viste i forhold til brukstid og vaner. Det var indikasjoner på at brukerne av cellekontorer var flinkere til å slukke lys og utstyr på eget kontor og i områdene rundt, enn det brukerne av kontorlandskap var. Resultatene fra målingene og undersøkelsene viser at differansen mellom behovet og forbruket av energi mange steder er høyt, og følgelig er også sparepotensialene høye i deler av installasjonen.

Tradisjonelle induksjonsovner bruker vekselstrøm for å indusere strømmer og varme opp større aluminiumsdeler. Effektiviteten til ovnene ligger normalt mellom 55-60%, noe som gir et stort forbedringspotensial. Ved å erstatte kobberspolene med spoler av superledere og vekselstrømmen med likestrøm vil tapene i spolene bli neglisjerbare. Aluminiumsdelen som skal varmes opp må da roteres for å se et vekslende felt, noe som medfører en samlet virkingsgrad for systemet på ca 90 %. SINTEF har sammen med flere samarbeidspartnere konstruert en 200kW induksjonsovn basert på MgB2 superleder. Denne rapporten tar for seg sammensammensetning og testing av en superledende spole for bruk i den planlagte induksjonsovnen. I rapporten er alle nødvendige deler og metoder for å sette sammen spolen beskrevet og forklart. Spolen består av totalt 16 disker som ble skjøtet sammen i serie. Hver disk er 550m og er viklet i en dobbel pannekake konstruksjon med 2 ganger 75 vindinger i hver disk. Under testingen brukte spolen 120 timer på å nå en stabil temperatur som lå under den kritisk temperatur for MgB2 superlederen (37K), og det ble gjort tester ved å føre en strøm på maks 10A gjennom spolen. Under strømtestene ble spenningsoppbygningen over alle skjøtene samt over alle spolediskene målt. Strømtestene avslørte at alle skjøtene i spolen hadde en motstand på under 60nΩ. En av spolediskene skilte seg ut og hadde en motstand på 66,6uΩ ved 10A, noe som tyder på et spoledisken har en defekt. Motstanden var for høy til å kunne gjøre tester med den planlagte strømstyrken på 200A. Induktansen til spolen ble målt til 4,9H.

Spenningskvaliteten har fått et større fokus de siste tiårene, dette har stor sammenheng med utviklingen av mye nytt og følsomt utstyr som kobles til kraftnettet. Utstyr som ofte består av mye kraftelektronikk. Bruk av simuleringsprogrammer vil være til stor støtte ved utvidelser i nettet, dette for å dokumentere at nette vil være innenfor kravene som er gitt i forskrift om leveringskvalitet i kraftsystemet, FoL. Dette kan spare utbygger for store kostnader som kan komme i ettertid av utbyggingen. Simuleringer vil også kunne gi raskere svar på forekomsten av feil med en lav hyppighet, sammenlignet med målinger ute i nettet. For å få en høy nøyaktighet må det kanskje måles over flere år. Ved simulering er det mulig å få svar innen få minutter. For finne ut hvordan situasjonen er i dag med tanke på simulering av leveringskvaliteten, ble det sendt ut en spørreundersøkelse til 123 FASIT ansvarlige i norske nettselskap. Resultatet fra denne undersøkelsen viser at 57 % av de 35 selskapene som svarte på undersøkelsen utførte simuleringer på en eller flere av de fenomenene som er omtalt i FoL. Årsaken til simuleringen er i hovedsak nye tilkoblinger eller ny produksjon. De fenomenene som flest simulerer på er langsomme variasjoner i spenningens RMS verdi, kortvarige over- og underspenninger og spenningssprang. Når det gjelder hvilken type programvare som brukes er det NetBas som er det dominerende programmet, fulgt av PSS/E. NetBas blir brukt i nesten 50 % av alle simuleringer som utføres av selskapene. PSS/E har kun en andel på litt over 10 %. Det er valgt å studere fenomenet spenningsdipp i nærmere detalj. Dette er et fenomen som er årsak til noen av de største kostnadene for et nettselskap etter avbruddskostnader. Det er utviklet et enkelt program i Matlab som gir en stokastisk simulering av spenningsdipp. Programmet baserer seg på Monte Carlo simulering, programmet bruker tre stokastiske variable: feilposisjon, overgangsmotstand og feiltype. Dette gir en fordeling av størrelsen på spenningsdipp ved to samleskinner på en radial. Brukeren taster inn data for linjen og kortsluttningsytelsen til det bakenforliggende nettet. Når det kommer til valg av simuleringsprogram for nettselskap, er det mange faktorer som er viktig å tenke på. Det kan være hvor ofte og omfattende selskapet skal simulere. Små selskaper kan være tjent med å leie inn konsulenttjenester for å gjøre jobben. Siden det vil kreve god kompetanse og stadig oppdatering for å kunne utføre slike simuleringer effektivt. Dette er også tilbakemeldinger som kom i forbindelse med spørreundersøkelsen. Et større selskap bør kunne se på muligheter for integrering mot eksisterende NIS systemer der alle data for nettet ligger lagret. Dette vil gjøre det enklere å få tilgang på inngangsdata. For å studere enkelte transiente fenomen vil det kreves en detaljert elektrisk modell av enkelte komponenter. Dette kan medføre en høy brukerterskel på mange programmer, særlig der modellen må bygges opp fra grunnen av.