Ett uppmärksammat problem i elnätet är den ökande halten av övertoner. I ett elnät som är fritt från övertoner förekommer enbart en grundton men i vissa fall förekommer strömmar, och spänningar, med andra frekvenser och då innehåller nätet en viss halt övertoner. När anslutna belastningar är olinjära uppstår övertoner. Det är huvudsakligen ökningen av dessa typer av belastningar i elnätet, till exempel elbilsladdning och datorer, som ger upphov till den ökande övertonshalten. Med anledning av ovannämnda problem med övertoner utförs detta examensarbetet på uppdrag av Megger Sweden AB i Stockholm. Syftet är att studera övertoners inverkan på relätripptiden hos ett elektromekaniskt överströmrelä som finns installerad i kraftnätets kontrollanläggningar. Testerna utförs med testinstrumentet Sverker 900 och med ett elektromekaniskt överströmsrelä, ett RI-relä av märket ASEA. För testning av RI-reläet följs en svensk standard, en kommande internationell standard och instruktioner från uppdragsgivare. Resultaten från testerna visar på skillnader mellan tripptiden med övertoner och tripptiden för enbart grundtonen. Slutsatser baserade på studiens resultat är dels att överströmsreläet är långsammare vid svaga strömmar, det vill säga 2,8 A och 3 A, eller har för långa tripptider i förhållande till beteendet utan övertoner. Dels att det är svårt att säkerställa ett signifikant samband mellan närvaron av övertoner och påverkan av relätripptiden vid medel och starka strömmar, det vill säga 4 A till 8 A, eller vid kortare tripptider. Baserat på studiens resultat skulle det vara intressant att testa med flera övertonsnivåer. En rekommendation för liknande framtida studier är att bara testa vid låga strömmar, långa tripptider och långsamma diskhastigheter, eftersom detta skulle underlätta möjligheten att uppnå en mer överskådlig resultatanalys. / A problem that has been noticed in the electricity grid is the increase in level of harmonics. In some cases, there may also be currents or voltages with frequencies that differ from the fundamental tone and this leads to the grid having harmonics meaning that when loads and components in the electricity grid are not sinusoidal, harmonics occur. For example, an increase in these types of loads e.g. charging an electric car or computers, in the electricity grid gives rise to an increasing harmonic content. In view of the aforementioned, this thesis has been carried out in collaboration with the Megger Sweden AB, Stockholm, as the official client for this study. The purpose here is to study the effect of harmonics on the relay trip time of an electromechanical overcurrent relay that is installed in the power grid's control facilities. The tests are performed with the test instrument Sverker 900 and an electromechanical overcurrent relay, ASEA RI. For testing the RI relay, a Swedish standard, an upcoming international standard as well as instructions from the client have been thoroughly followed and applied. The results of the tests shows the difference between the trip time with harmonics and the trip time for the fundamental tone. Conclusions based on the results are partly that the overcurrent relay is slower at weak currents, that is 2.8A and 3A respectively, as well as for long trip times in relation to the behavior without harmonics. According to the findings conducted herein, there is no significant correlation between the presence of harmonics and the influence of the relay trip time on medium and strong currents, between 4A-8A, or on shorter trip times. By reason of the time constraint experienced in conducting this study, the results and findings reached leaves a sound potential and promise for future tests conducted at different harmonic levels. A future recommendation for similar studies will be to test only at low currents, long trip times and slow disk speeds as this would facilitate the possibility of fulfilling a more robust result analysis.

Vattenfall Eldistribution arbetar med att förbereda organisationen för projektet "Starta Sverige" vilket är skapat av Svenska kraftnät. Målet är att genom gemensam samverkan mellan olika driftcentraler minimera problem vid driftuppbyggnad efter ett större komplexts tamnätsavbrott. Detta arbete syftar till att hjälpa Vattenfall Eldistributions driftoperatörer att på enklast, snabbast och säkrast möjliga sätt bistå strategin framtagen i Starta Sverige vid lasttillkoppling efter en större nätkollaps. Det görs genom att skapa en översiktsbild till Vattenfall Eldistributions driftsystem som innehåller all relevant information. Ovanstående mål uppnås genom att utföra intervjuer med driftoperatörer och driftsystemspecialister i syfte att förstå önskemål och förväntningar till översiktsbilden men också för att hålla översiktsbilden inom driftsystemets tekniska begränsningar. Flera iterationer har genomförts där ändringar av översiktsbilden skett utifrån de uppföljningsintervjuer som utförts. Resultatet är en översiktsbild ungefär i storlek av ett A4-papper. Tekniska begräsningar hindrar en del av driftoperatörernas önskemål från att bli verklighet, exempelvis diagrammed kvarstående aktiv effekt att koppla in efter ett större avbrott. Resultatet av arbetet blir en översiktsbild för varje av Starta Sveriges åtta zoner. Översiktsbilden innehåller information om relevanta stationer, reaktiva komponenter, lindningskopplare samt spänning och frekvens i stamnätspunkten. Fokus läggs också på att uppvisa den tillkopplade och tilldelade aktiva effekten inom varje stamnätspunkt eftersom det enligt Starta Sveriges anvisningar är av prioritet vid nätåteruppbyggnad. Översiktsbilden kommer att implementeras i driftsystemet samma år som publiceringen avdenna rapport, men en exempelbild i Vattenfall Eldistributions driftsystem finns redan tillgänglig. Eftersom bilden enbart är tänkt att nyttjas vid ett större stamnätsavbrott råder osäkerhet kring när den faktiska användningen kommer ske. / Vattenfall is currently working to meet the instructions of the project "Starta Sverige" that is created by the Swedish transmission system operators in which a cooperation between different control rooms and control centers will minimize problems during power system restoration after a major disturbance. This work aims to aid the completion of the strategy in Starta Sverige for the control-room operators at Vattenfall to reconnect load after a system failure in the simplest, fastest and safest way possible. This will be done through development of a schematic overview to Vattenfall's operating system. The way to achieve this is to conduct interviews with control-room operators and operating system specialists with the purpose of understanding their needs and expectations but also to understand the technical limitations of the operating system. The development has been performed in an iterative way where follow-up interviews weremade to persistently improve the schematic overview. The result is a schematic overview roughly the size of an A4-papersheet. Technical limitations prevent some of the control-room operator's wishes to become reality, such asto use graphs to show the remaining active power to reconnect. There is one schematic overview to each of the eight zones of Starta Sverige in Sweden which will contain information about relevant stations, reactive components and transformer taps in addition to showing the voltage and frequency for the connection point to the national transmission grid. According to the instructions of Starta Sverige there is a priority to present the available and used active power since this information is important for system restoration. The schematic overview is planned to be implemented in the operating system the same year as the publication of this report, although currently an example is accessible in Vattenfall's operating system. Since the schematic overview is planned to be used after amajor system breakdown there's an uncertainty when the actual use will be.

The Internet of Things is a hot topic for development and research right now.More and more devices get connected to Internet by the day, but sometimesthe security of Internet of Things is neglected. Xavitech is a manufacturer ofmicropump that is interested in entering the world of the Internet of Things.This thesis work was done in collaboration with Xavitech and aimed to look athow an Internet of Things implementation for micropump could be designedin a secure manner. The goal was to design a concept application that could beused to calibrate micropumps remotely over the Internet, with primary focuson the security of the in-flight data of the application. When designing thisconcept application, an existing reference model was used as a basis. Acomparison of different protocols suitability for this application was alsoconducted and the most suitable protocol was implemented. The conceptapplication proposed in this thesis is an example of how a secure Internet ofThings implementation for micropumps can be designed.

Immobilizers are security systems that are set up and installed in modern vehicles in order to prevent thieves from starting the vehicles. The idea is that if any wrong keys are used to start the vehicle, the immobilizer detects the wrong key and start the immobilization procedure to stop the vehicle from turning on. The vehicle ignition key (key transponder or key fob) is one of the important components in an immobilizer system. An ignition key in an immobilizer system has a Radio Frequency Identification Device (RFID) chip inside it. This RFID chip holds a specific encryption algorithm and particular number of bits (encryption key bits) in itself. Using the encryption algorithm and encryption key bits, RFID chip inside the key authenticates and identifies itself as the right key to the immobilizer system in order to disable the immobilization procedure and start the vehicle. However, there are two ways thieves can disable the immobilization procedure and start the vehicle. The first approach is by discovering the specific encryption algorithm and key bits in the right key transponder (RFID) and using them to duplicate the correct RFID chip to disable the immobilization procedure and start the vehicle. The second approach is by exploiting the vulnerabilities and weaknesses in vehicle security network (CAN bus) to bypass the immobilizer and manipulate the immobilization procedure to start the vehicle. Scania vehicles are not using the most secure RFID and immobilization procedures, hence they are vulnerable to two vehicle theft approaches above. Therefore in this thesis project, I have done research and investigation on Scania vehicles key transponder (RFID) and analyzed their immobilization procedures in order to identify the roots and origins of vulnerabilities in Scania RFID and immobilization procedures. As the first result of this thesis work, I have found and proposed an RFID chip having one of the strongest encryption algorithms and proper number of encryption key bits for all Scania vehicles. As the second result of this thesis project, I have proposed and introduced two new individual immobilization procedures exclusively for Scania hybrid and electrical vehicles. Both proposed RFID (encryption algorithm) and immobilization procedures will be implemented in Scania vehicles in near future and will increase the security of Scania immobilizers significantly.

This thesis aims first to investigate whether solar panels on the container can provide the process of desalination with energy at the desired location, as well as to dimension a photovoltaic system and battery storage that can run the facility off-grid. Then investigate whether solar cells can be an effective energy solution for Millennium Desalination Device (MDD). The results of this study show that the most annual solar production from containers is 11 510 kWh in Gobabeb, Namibia with a modular efficiency of 22,8 %, which corresponds to 8,2 % operating time per year and is the longest operating time that can be obtained from the all three scenarios. This means that with existing technology and only solar panels on the container, desalination plant is impossible to drive all year round off-grid. The installed power for driving 100 % operating time for one year is 141 kW in Gobabeb and 179 kW in Visby, the corresponding module surface will be lowest 618 m2 and 1184 m2 with modular efficiency of 22,8 %, but there are no additional spaces for all equipment like MDD, solar cells and battery in the container. If the operating time drops to 50 %, the installed power will be 71 kW in Gobabeb, the corresponding module surface will be lowest 415 m2 and battery storage capacity will be at least 160 kWh. Net volume with all equipment will be less than the volume of the container. The cost will be at least 0.2 Swedish kronor per liter of pure water produced with a life of 25 year for solar modules. Usage fee per liter of delivered water is 0.03 Swedish kronor in Gotland and it means MDD is not a cost-effective solution for Gotland at nowadays. But costs may fall in the future with the price reduction of solar cells and batteries. For water shortage areas, this can be a valuable way to solve the water crisis, but it also depends mostly on the area’s water price.

BAE Systems Hägglunds använder säkringar och kontaktorer eller reläer för deras 28V-system. Kostnaden för dessa är höga och dem är utrymmeskrävande. Syftet med detta projekt var att utveckla den befintliga elcentralen. Målet var att konstruera ett system baserat på halvledarrelä med strömmätning samt säkerhetsfunktion. En prototyp konstruerades med en spänningsregulator, fyra optokopplare, två kylflänsar, och två stycken transistorer. Resultatet visade att prototypen tolererade strömmar upp till 70A på en 24V-spänning. Prototypen tolererade sannolikt högre spänning och ström, men detta kunde inte verifieras.

A sedentary lifestyle can induce health related problems including pressure ulcers. Pro­longed sitting inadequacies constitute a risk for pressure ulcer to many individuals, in particular people with disabilities and re­duced mobility. The measurement of distributed pressure and detection of irregular sitting postures are essential in prevention of the risk of developing pres­sure ulcers. In this thesis, a screen-printed pressure sensor for a large area is presented, with the objective of measuring the distributed pressure of a seated per­son in a wheelchair. The conductors and interdigital patterns are printed with silver-based ink. A blend of a non-conductive and a low resis­tive ink is used for customized resistance for an optimal sensing range of the pressure sensor. The effect of moisture and temper­ature are realized in an environment chamber. For characterization, other key performance tests such as repeatability, drift and flexibility are carried out. The surface morphology is carried out for structural analysis of printed samples. The sensor data is acquired and processed using an 8-bit ATmega-2560 micro­controller and wirelessly transmitted to a PC for post-processing, storage and analysis. For real-time data presentation of dis­tributed pressure points, a GUI has been developed to display the values ob­tained from the large area sensor. The detection of four sit­ting pos­tures; forward leaning, backward leaning, left leaning and right leaning along with a normal sitting posture is attained. An analysis for stretchable printed tracks has been conducted to investigate the changes in electrical resistance using elon­ga­tion tests, surface morphology and EDS. The optimal curing time and tem­per­ature were investigated to manufacture stretchable conductive tracks. In summary, the contributions in this thesis provides an effective approach regarding pressure distribution measurement and recognizing irregular sitting postures for wheelchair users. / <p>Vid tidpunkten för framläggningen av avhandlingen var följande delarbete opublicerat: delarbete 3 (accepterat).</p><p>At the time of the defence the following paper was unpublished: paper 3 (accepted).</p>

This thesis carries out an analysis of PV panel installations in the region of Östergarnslandet, situated in the Swedish island of Gotland. A low-voltage grid of 0.4 kV in the region is examined with the help of software Open DSS. This is done with the data provided by the distribution grid owner, Gotlands Elnät AB (GEAB). The potential impacts created by the PV installations in terms of exceeding currents, voltages and harmonics are assessed and thereby the hosting capacity of Solar PV in the houses and on the whole grid is studied.   Moreover, a theoretical review of the Smart Energy Management System (SEMS) is investigated about the performance and the devices involved in the system. Also, a battery which is a part of SEMS is modelled, taking into account the production and consumption of a single household connected in the grid. The battery sizes for various PV installations at the home is suggested via NPV analysis with the intention to increase the self-consumption and to reduce the cost of the electricity bill. In addition, a survey is conducted in the region with support from the Department of Earth Sciences, Uppsala University Campus Gotland. The survey is made to determine the attitude of the people in Östergarnslandet towards an energy transition. The results show that the maximum amount that can be installed or the hosting capacity of solar in the studied grid is 120 kW. From the simulations, it shows that the impacts created by these PV installations do not violate the specified Grid norms. From the theoretical analysis, SEMS is found to be a better solution for energy management at homes. The performance study done shows that 33 % of the solar energy produced in the home is directly used at the time of production. The remaining energy is used for battery charging for the future supply of power and feeding to the grid. The battery modelled for 10- kW PV installation in the home is found to be 9-kWh and the same for a 15-kW installation. Meanwhile, for a 20- kW installation, a 15-kWh battery is found to be ideal from the study. The survey conducted in the region has turned out to be positive as people are supportive of the energy transition. The responders have marked photovoltaics as the prime option for investment in energy production which assures that it has a good future in the area.

Printed circuit boards are getting increasingly more complicated, as the electronics industry seeks methods to stay leading in modern technology. The competition to attain more economical solutions in terms of increasing complexity, integrity, optimum functionality, impose on design engineers to look for new horizons of solutions, then simulating and testing them theoretically and practically, before putting them into the labor market. In multi-layer boards, the issue of maintaining signal quality while transmitting it between different layers arises, it is a big deal, especially when dealing with RF signals, where each component through which the signal passes must be handled and designed with extreme accuracy to be received at output with a maximum matching with the input signal.  Vertical Interconnect Access (VIA) is the purpose of this thesis. The effect of geometrical shape and the dimensions such as pad, hole and clearance on the impedance due to parasitic capacitance and inductance, consequently on the reflection and attenuation of the passing RF signal passing through was investigated. Besides, a minimized reflection and attenuation was the aim of this project when signals with the frequencies of 2.4 and 5 GHz would pass through the VIA.

Supplying power to equipment always imposes a risk of damaging it. This risk is apparent in every application whether it be an industrial or a home appliance. One of these harmful occurrences is something like lightning which introduces a potentially harmful voltage in the system. To reduce the risk of damage significantly an over-voltage protection device is needed. Devices which deal with this problem are common in any electrical equipment and this report deals with the construction and evaluation of one such unit. The device or equipment needing protection in this case is an industrial underwater robot built by Ocean Robotics. In order for this robot to operate safely it needs several protective measures where an over-voltage protection system is one of them. This system provides protection against over-voltages appearing on the main cable supplying the robot, where the input voltage ranges from 200 to 600 volts. As the desired voltage output range from the over-voltage system is 250 to 350 volts it must be able to handle significant power in some cases. Due to the restrictions on functionality given by the contractor a novel way of achieving the goals was tested. The completed prototype can only dissipate 70 watts of power which is far from the required 1500 watts which was specified in the sheet of requirements. However, this system could be used to protect equipment with lower requirements for power handling capability and with added time and effort it could possibly meet the requirements for this project as well.