The transformer is one of the most common and most important electric machines for power companies. Cost of investment and the economic worth of a transformer are counted in millions of SEK. Because of that, proper maintenance actions that may lead to longer technical life time should be the aim in all situations. The aim with the report was to perform transformer diagnosis by dissolved gas analysis on Umeå Energi AB´s power transformers and a risk assessment. The report should also contribute to longer life time for the transformers. Oil samples were taken from each transformer two times. The first sample in summer 2013 and the second in April 2014. The gas concentrations in the samples was measured by an portable gas analyzing monitor. The samples were analyzed regarding to gas concentrations and the gas rate of change. The analyze was based on scientific methods like the total amount of dissolved combustible gases, Duvals triangle and Rogers ratios. The risk assessment was made as an internal comparison between Umeå Energi´s transformers. The results of the study showed large gas concentrations in several transformers in both times of sampling. The high concentrations appeared in old as well as in newer transformers. Therefore can the presence of gases not only be explained by natural aging, and different fault types can be suspected in some of the transformers. Duval´s triangle and Rogers ratios indicated various fault types. One of the transformers was immediately taken out of service after the first sample because of high level of a separate gas and the discussion about what actions to take was ongoing. A number of other transformers were taken into further consideration. Conclusions of the report were that transformer diagnosis is a very complex science where it is important to collect as much adequate information as possible to be able to make a correct analyze for every single transformer and to take proper actions. To be able to secure fault free operation of the power grid and to minimize the risk of wasting economic and material resources, and from a personal safety point of view, the power transformers must be maintained and tested regularly and be based on scientific principles. Faults in power transformers can lead to large impact on the environment and large effect on society if electricity is not available.

Hitachi ABB Power Grids is a world leading manufacturer of power transformers, operating on an increasingly competitive market. With the advancements in digitalization and electrification, the production of power transformers has been subject of higher demands, both in terms of product quality and production efficiency. To stay ahead of market rivals, constant development of the business and its production processes is necessary, which has been enabled by increased access to innovative technical solutions. Novel appliances and areas of development has been investigated, of which 3D-scanning is one of the promising technologies that has proven useful in the manufacturing industry.  The purpose of this study has been to map the production process of power transformer manufacturing at Hitachi ABB Power Grids, with the intention of identifying potential areas for use of 3D-scanning technology in quality management. By analyzing each individual production segment, the study has sought to answer to where in the production system that 3D-scanning technology can be beneficial, what type of improvements it can contribute with, and what risks and limitations that using the technology might entail.  The results were obtained by analyzing empirical data, collected through both qualitative and quantitative methods. Interviews with employees and on-site observations has been the main sources of data, together with documentation and statistics from the company’s own data bases.  Central factors that the analysis was built upon are the registered costs of failure and reported quality defects, combined with the appropriateness of 3D-scanning technology in each segment regarding the practical usability, advantage in time, economic profitability, and the feasibility of implementation in the production system. A value assessment was made of the device’s potential, leading to identifying improvements in transparency, traceability, and efficiency. Some of the discussed drawbacks were limited visual access, faulty handling of the equipment, and excessive reliance on the technology. / Hitachi ABB Power Grids är en världsledande tillverkare av krafttransformatorer, agerandes på en alltmer konkurrensbenägen marknad. Med digitaliseringens och elektrifieringens framfart ställs högre krav på produktionen av krafttransformatorer, både gällande produktkvalitet och produktionseffektivitet. För att bibehålla en ledande position krävs därför ständig utveckling av verksamheten och dess processer, vilket bland annat möjliggjorts av den ökade tillgången till innovativa tekniska lösningar. Nya verktyg och förbättringsområden undersöks, varpå en av de uppmärksammade teknikerna är 3D-skanning, vilket visat sig användbart inom tillverkningsindustrin.  Syftet med studien har varit att kartlägga processen för krafttransformatortillverkning hos fallstudieföretaget Hitachi ABB Power Grids, med avsikt att identifiera möjligheterna kring användning av 3D-skanningsteknik i kvalitetsarbetet. Genom att undersöka varje individuellt delmoment i produktionsprocessen har studien sökt besvara var i produktionssystemet som 3D-skanningstekniken kan medföra förbättringar, vilken typ av förbättringar som kan åstadkommas, samt de risker och begränsningar som användning av tekniken eventuellt kan medföra.  Resultaten erhölls genom analys av empiriska data som samlats in genom både kvalitativa och kvantitativa metoder. Intervjuer med personal och observationer på anläggningen har utgjort de huvudsakliga källorna till information, tillsammans med dokumentation och statistik från företagets interna databaser.  Centrala faktorer som analysen har byggt på är produktionens registrerade felkostnader och rapporterade kvalitetsfel, i kombination med 3D-skanningsteknikens lämplighet för respektive avsnitt gällande praktisk användbarhet, tidsmässig fördel, ekonomisk lönsamhet och implementerbarhet i produktionssystemet. En värdering gjordes därefter av teknikens potential, och förbättringar i form av transparens, spårbarhet och effektivitet kunde identifieras. Några av de brister som uppmärksammades var begränsad visuell åtkomst, felaktig manövrering av utrustningen och överdriven tillförlitlighet till tekniken.

Mälarenergi’s vision is a world where we live and operate together without climate impact. This degree project has examined which opportunities Mälarenergi Elnät has in order to work towards this vision by looking more closely at whether their bigger substations can become self-sufficient in terms of heating, cooling and battery charging. The purpose of this degree project was to investigate how heat recovery from the substations’ transformers and the installation of PV-systems could contribute to both more environmentally friendly and self-sufficient substations. In addition to that, the economics and how this would affect the Swedish power grid regulation were of interest. The thesis was based on current values and data for oil temperatures and installed power in three of Mälarenergi Elnät’s substations. In addition to this, the thesis also includes a literature study, where previous research in heat transfer from power transformers, up-to-date information about PV-installations and the power grid regulation in Sweden were studied. The results of the thesis showed that both PV-installations and heat exchange for heating the station buildings could be of great benefit for Mälarenergi Elnät. In all but one case, the energy saving measures resulted in lower life cycle costs than if no measures were taken. It shows that the measures investigated in the thesis are not only good from an environmental perspective, but also has economic profitability.

Transformatorn har en viktig uppgift för att elsystemet ska fungera optimalt och det är därav väldigt viktigt att den inte går sönder genom att exempelvis överhettas. Från att transformatorn har varit placerad utomhus har det nu blivit allt vanligare att placera den i en omslutande byggnad, vilket påverkar effektiviteten för kylningen av transformatorn. Detta eftersom hastigheten på det passerande luftflödet kring transformatorn blir lägre vilket leder till att temperaturen i luften runtomkring ökar. I detta examensarbete undersöktes lufttemperaturen i en transformatorstation i Västernorrland, i syfte att se hur transformatorn klarar av de belastningar och utomhustemperaturer som den utsätts för. Detta för att kunna säkerställa att temperaturgränser och riktlinjer för interna och externa temperaturer för en transformator uppfylls. Transformatorn som användes i undersökningen har en maximal skenbar effekt på 16 MVA och använder sig av kylsystemet ONAN. Byggnaden runtomkring transformatorn har två ventilationsluckor på nedre långsidan, samt två ventilationsluckor på övre kortsidan.  Målet med undersökningen var att genomföra en teoretisk analys av hur kylningen i den valda transformatorstationen dimensioneras, där simuleringar även skulle göras i syfte att validera den teoretiska analysen. De belastningar som undersökts har utgått ifrån tillhandahållna data ifrån den högsta lasten under en vanlig sommar- och vinterdag. Ett framtida fall har även undersökts där lasten antas gå på märkeffekt under en längre tidsperiod samt under en väldigt varm sommardag, för att se hur hårt transformatorn kan belastas i extrema förhållanden utan att gränser och riktlinjer överskrids. Det framtida fallet har delats upp i två scenarier, extremfall 20 samt extremfall 30, där skillnaden är vilken temperatur in i transformatorstationen de har. Alternativa lösningar för ventilationsluckorna har även studerats, gällande placering på väggar, storlekar samt gallers modell. Matematiska beräkningsmodeller för bland annat luftflödet, stationstemperaturen samt lindningsoch oljetemperaturer utvecklades fram under arbetet gång, vilka samlades i en Excel beräkningsmall. Simuleringar av byggnaden och transformatorn gjordes i COMSOL Multiphysics, där både 2D och 3D modeller undersöktes i syfte att dels analysera värmespridningen i oljan, dels den naturliga ventilationen. Utifrån de matematiska beräkningsmodellerna framgick det att vinterfallet körde på ca 49% belastning, medan sommarfallet körde på ca 10% belastning. Dessa båda fallen klarade alla gränser och riktlinjer kring externa och interna temperaturer för alla areastorlekar, placeringar och gallersmodeller som testades. I extremfallen uppfylldes de interna temperaturökningsgränserna, men extremfall 30 klarade inte den externa temperaturgränsen i något simuleringstest. Skulle ett extremfall 30 i framtiden inträffa, bör fläktar vid radiatorerna eller ventilationsluckorna övervägas, alternativt en större lucköppning där det enligt framräknade resultat behövs en förstoring av öppningarna på 57%. Ytterligare ett alternativ skulle kunna vara att placera ventilationsluckorna i taket, då detta visade sig ge bästa möjliga kylning av transformatorn i simuleringarna. Detta examensarbete skulle kunna användas som en grund inför framtida undersökningar och den framarbetade Excel beräkningsmallen kan användas som riktlinje vid dimensionering av inomhustransformatorstationer. / The transformer plays a crucial role for the electrical system to function optimally, making its reliability vital to prevent issues such as overheating. Traditionally, the transformer has been positioned outdoors. Nowadays it has become increasingly common to house transformers in enclosed buildings, which affects the cooling efficiency of the transformer. This enclosure reduces the speed of airflow around the transformer, subsequently raising the ambient air temperature. In this thesis, the air temperature in a transformer station in Västernorrland was investigated, to assess how the transformer withstands the loads and external temperatures it encounters. This to ensure that requirements and guidelines for internal and external temperatures for the transformer are met. The transformer used in the study has a maximum apparent power of 16 MVA and uses the ONAN cooling system. The enclosing building is equipped with two ventilation hatches on the longer lower side and two on the shorter upper side.  The aim of the investigation was to conduct a theoretical analysis of the cooling system’s dimensions at the selected substation, complemented by simulations to validate the theoretical findings. The loads investigated have been based on the data provided from the highest load during a normal summer and winter day. Additionally, a future scenario was explored where the transformer operates at rated power for extended periods during a very hot summer day to determine the maximum load the transformer can handle under extreme conditions without breaching the set requirements and guidelines. The future case has been divided into two scenarios, extreme case 20 and extreme case 30, where the difference is what temperature into the substation they have. Alternative design solutions for the ventilation hatches have also been studied, regarding placement on walls, sizes, and fire damper model. Mathematical calculation models for, among other things, the air flow, station temperature, winding- and oil temperatures were developed during the project and compiled into an Excel calculation template. Simulations of the building and the transformer were made in COMSOL Multiphysics, analysing both 2D and 3D models with the aim of studying the heat spread in the oil and the natural ventilation.  The mathematical models showed that the winter scenario operated at approximately 49% load, while the summer scenario operated at about 10% load. These two cases passed all requirements and guidelines regarding external and internal temperatures for all tested hatch sizes and locations. In the extreme cases, the internal temperature rise requirement was met. However, extreme 30 failed to meet the external temperature requirement in any simulation test. Should an extreme case 30 occur in the future, fans at the cooling fins or ventilation hatches may be necessary, or potentially enlarging the hatch openings by 57% as suggested by the calculations. Another alternative could be placing the ventilation hatches on the roof, as this arrangement provided optimal cooling in the simulations. This thesis could be used as a basis for future investigations and the developed Excel calculation template can be used as a guideline when dimensioning indoor transformer stations.