Denna studie undersöker de ekonomiska och miljömässiga hänsyn som tagits vid utbyggnaden av de svenska elstamnätet under perioden 1980-2010. Dokument från både mindre och större utbyggnadsprojekt har använts för att identifiera och analysera dessa hänsynstaganden. Resultaten visar att nivån av hänsyn till ekonomiska och miljömässiga intressen överlag ökat markant under perioden, särskilt i och med lagändringar som avkrävt att hänsyn tas till särskilda intressen. Vissa intressen saknade dock välutvecklade hänsynstaganden även i senare delen av materialet, något som bör tas i beaktan vid framtida stamnätsutbyggnader. / This study has examined the economic and environmental considerations taken during the expansion of the Swedish power grid between 1980-2010. Documents from minor and major grid expansions have been used to locate and analyse these considerations. The results point towards a sharp increase in the level of considerations taken to economic and environmental interests during course of the period, especially in response to legal developments mandating certain interests to be brought into consideration. However, some of the interests studied lacked well-developed considerations even in the later parts of the period, something that should be taken into account when deliberating future grid expansions.

Svenska kraftnät, which is the authority responsible for the Swedish national grid, performs cost-benefit analysis (CBA) to assess which of different investment projects that are of greatest benefit to society. The environmental impacts are also estimated during this analysis. In this paper, a tool for estimating the environmental impacts during the lifetime of a grid component has been developed with the purpose of enabling a more complete environmental evaluation. A life cycle assessment was performed to develop the tool. The impact categories that have been studied are climate change (kg CO2-eq), freshwater eutrophication (kg P-eq), particulate matter formation (kg PM10-eq) and terrestrial acidification (kg SO2-eq). To be able to compare the environmental effects with other costs and benefits in the CBA a monetary valuation of the impact categories has been established. The result of this paper indicates that the AC-overhead line is the technology that contributes with the lowest environmental impact during the life cycle. This result, however, is obtained when analyzing different technical alternatives with the same preconditions, which rarely is the case in real projects. The result can therefore differ between different investment projects. The tool enables an assessment of the environmental impacts of different investment projects in the Swedish national grid, and is therefore an important part of the cost-benefit analysis to determine which alternative is best suited.

During the period 2009-2013, investments in the Swedish national grid increase by a factor of ten compared to previous years. In order to fulfil their mission to manage the national grid in a safe, efficient and environmentally sound way, Svenska Kraftnät (Swedish National Grid) needs to take all these perspectives into account while planning new investments. To compare and relate perspectives of technology, economy and environment the same yard stick must be used. That yard stick is commonly money. A problem arises however as environmental issues are difficult to price. The purpose of this master’s degree project was to develop a tool for evaluation of environmental impact related to investments in the Swedish national grid. It was initiated by and conducted at the unit for Grid development at Svenska Kraftnät. A life cycle perspective  was used and the following stages were identified: material production, construction, operation and decommissioning. The environmental impact from these stages was sorted into ten impact categories using the LCIA method ReCiPe 2008 and then two economical evaluations were performed: one at midpoint level and one at endpoint level. Also included in the evaluation were the change in power losses or in the power production mix and the visual impact coming from overhead transmission lines. The tool was implemented in Excel and offers the possibility to evaluate the environmental impact from five different power line technologies (per km), substation line bays (per bay), transformers (per piece) and reactors (per piece). The main results show that AC land cable has a significantly higher environmental impact and cost than the other power line technologies. Material production and construction are the life cycle stages that contribute the most to the environmental cost. The impact categories that affect the environmental cost the most are climate change (for midpoint evaluation) and resource depletion (for endpoint evaluation). When the investment affects the power production mix, e.g. by changing the transmission capacity to another country, the subsequent environmental impact can be very influential on the total environmental cost of the investment.

The losses on the Swedish national power grid correspond to 2,8 % of the total energy input on the grid and even a small reduction of this can therfore be worth introducing. The purpose of the thesis is to summarise different ways to influence the losses on the Swedish national grid as well as calculating the possible loss reduction from two of these influence possibilities. The study has been requested by the Swidish transmission system operator, Svenska kraftnät. The study is limited to the Swedish power grid with voltages 400 kV and 220 kV. The influence possibilities exclude anything that demand physical changes to be made on the power grid. The study is mostly based on interviews with people that have insight in the isssue, ss well as a study on relevant literature. The result show that there are seven different possible ways to reduce the losses on the power grid. What extent of measures that is necessary for instating these loss reductions varies, but thay arr described in the study. Calculations on two of these loss influences where made and showed that a loss reduction of around 740 MWh/year can be achieved from optimizing the usage of power transformers on the grid. Furthermore, other calculations show that if the maintenance method, live work, had been used for the past ten years, losses could have been decreased by approximately 58 800 MWh. This shows that the possible loss reduction can vary a lot depending on which method you use.

This report addresses the parameter settings for a protective relay designed to safeguard a 15 kW wind turbine located in Rimbo, Norrtälje municipality, against unintentional islanding. This type of situation arises when distributed energy resources continue to supply local loads, even if the main grid has been unintentionally disconnected. The previous protection system experienced malfunctions and has been replaced with a new protective relay to ensure reliable protection. The new protective relay introduces two parameters (relay settings) associated with unintentional islanding protection function, namely RoCoF (rate of change of frequency) hysteresis, and delay, which were not defined in the previous protective relay. This report aims to determine suitable relay settings and verify that the relay operates as intended, taking into account both local and national requirements for connected generators. When these requirements did not specify or recommend a specific value, reference was made to practices in neighbouring countries, and consideration was given to the generator owner's benefit. Testing the relay with the chosen settings was crucial to ensure a correct understanding and accurate input of the settings. The testing was conducted in a laboratory environment with carefully defined signals of controlled frequency and voltage, while the relay's trip output was logged. The report includes information about the current settings along with a theoretical background to explain their functionality. It also presents test results and the provided information on parameter configurations. Additionally, recommended settings for RoCoF hysteresis and implementation delay are suggested, aiming to enhance protection against inadvertent operation. The results confirmed that the relay can be used in Rimbo, Norrtälje municipality, according to the parameters described in the report. / Denna rapport behandlar parameterinställningar för ett skyddsrelä som skyddar en 15 kW vindkraftsturbin i Rimbo, Norrtälje kommun, mot oavsiktlig ödrift. Denna typ av situation uppstår när distribuerade energiresurser försätter att mata lokala laster, även om stamnätet har kopplats bort oavsiktlig. Det tidigare skyddssystemet har blivit skadat och ersatt med ett nytt skyddsrelä för att säkerställa ett tillförlitligt skydd. Det nya skyddsreläet introducerar två parametrar (reläinställningar) relaterade till skyddsfunktionen mot oavsiktlig ödrift, nämligen RoCoF (frekvensderivata intervall) hysteres och fördröjning, som inte var definierade i det tidigare skyddsrelät. Denna rapport syftar till att fastställa lämpliga reläinställningar och verifiera att reläet fungerar enligt avsikt, med hänsyn till både lokala och nationella krav för anslutna generatorer. När dessa krav inte specificerade eller rekommenderade ett specifikt värde, refererades det till praxis i närliggande länder och hänsyn togs till generatorägarens fördel. Testning av reläet med de valda inställningarna var av central betydelse för att säkerställa en korrekt förståelse och korrekt inmatning av inställningarna. Testningen utfördes i en laborationsmiljö med noggrant definierade signaler av kontrollerad frekvens och spänning, samtidigt som reläets utlösningsutgång loggades.  Rapporten inkluderar information om de aktuella inställningarna tillsammans med en teoretisk bakgrund för att förklara deras funktion. Den presenterar också resultat från tester och den tillhandahållna informationen om parameterinställningar. Dessutom rekommenderas inställningar för RoCoF-hysteres och fördröjning för implementering, med målet att förbättra skyddet mot oavsiktlig ödrift. Resultaten konstaterade att reläet kan användas i Rimbo, Norrtälje kommun enligt de parametrar som beskrivs i rapporten.

Svenska kraftnät (Swedish National Grid) is the transmission system operator in Sweden and is responsible for maintaining and developing the Swedish transmission grid. One of the tasks included in this responsibility is transmission expansion planning, which means analyzing and planning the capacity in the future transmission grid for the requested load and generation. Historically, the N-1-criterion has been used to evaluate the reliability in transmission grid expansion planning. This criterion is deterministic, which means that all failures in the grid are considered equally, regardless of the differences in probability. In a system with an increased share of intermittent energy sources and load, it is increasingly demanding to plan and build a system that is N-1-secure in all situations. Probabilistic Risk Assessment (PRA) is a complementing method that takes the probability and consequence of different faults into consideration. The possible benefits of using PRA are higher utilization of the power grid, greater system operating flexibility, better support for system planning, and an overall optimization of socio-economic benefits. In this master thesis project, a method for PRA in transmission expansion planning at Svenska kraftnät is proposed. The method consists of three steps: generation of operating states, contingency analysis, and reliability assessment. Historical frequency and duration of faults in the transmission grid are used to estimate the probability of different contingencies. The method results in three reliability measures for the system: expected energy not supplied (MWh/year), expected duration of outages (h/year), and expected duration of overloads (h/year). The three reliability measures are combined into a composite comparison index, which can be used to compare different alternatives in transmission expansion planning. The proposed method is tested on a PSS/E model of the Swedish transmission grid and 14 different operating states. Four different investment alternatives are analyzed, including changes in load and generation, and grid reinforcements. The conclusion is that the proposed method is a useful tool for power system analysis at Svenska kraftnät and that the process for generating the operating states must be further developed. / Historiskt har det deterministiska N-1-kriteriet använts för att bedöma transmissionsnätets tillförlitlighet vid långsiktig nätplanering. Detta innebär att systemet ska dimensioneras för att klara ett bortfall av någon systemkomponent under värsta tänkbara driftfall, exempelvis topplasttimmen. I ett elsystem med alltmer intermittent förbrukning och produktion kan det dels vara svårt att veta vad som är det värsta tänkbara fallet, och dels kan det bli mycket kostsamt att dimensionera ett system som är N-1-säkert i alla lägen. Därför är det intressant att införa kompletterande probabilistiska verktyg. I detta examensjobb föreslås en metod för att beräkna och använda probabilistiska mått för att bedöma transmissionsnätets tillförlitlighet. Metoden använder flera tänkbara driftfall med varierande sannolikhet och värden på hur sannolika olika typer av fel i systemet är. Tänkbara fel analyseras och resulterar i mått på systemets förväntade överlaster och avbrott, uttryckt i timmar per år och energi per år. Dessa nyckeltal kombineras till ett sammanvägt mått, som kan användas för att jämföra olika nätanslutningar och investeringsalternativ.