Sökresultat:
455 Uppsatser om Voltage stability - Sida 21 av 31
Analys av mellanspänningsnätet i centrala delar av Västerås stad
The dependency of continuous electricity supply is high in the Swedish society today, at the same time no one is willing to pay for a too costly or over dimensioned power distribution system. The owners of the distribution systems are the ones responsible for this balance act of maintaining a high quality of electricity delivery to customers at a reasonable cost.In this master thesis a limited part of the primary distribution system (10 kV), owned by Mälarenergi Elnät AB and located in the city centre of Västerås, was chosen for a deeper analysis of its reliability. Its ability to handle outages of system components (N-1 and N-2 contingency analysis) was investigated to find out potential weak spots and parts of the grid that showed signs of being overdimensioned.The results of the performed simulations showed that in 74 % of the studied N-1 contingencies cases, consisting of outages of a bus bar in a distribution substation, the system could handle this without causing outages in other parts of the grid. For the N-2 contingencies 61 % passed the test. It was also found that one of the two included high voltage substations could alone supply the investigated part of the grid.
Den djupa muskelfunktionen hos kvinnliga elitvolleybollspelare : En studie om transversus abdominis funktion påverkas av stabilitetsträning.
Background and purpose: Volleyball requires a lot of the human body, andeffective core stability is necessary for the athlete. Our muscles cooperate as achain of motions and core stabilization is the base for the moving muscles.The most well-known stabilization muscle is m.transversus abdominis (TrA).The purpose of the present study was to evaluate the function of TrA inSwedish female elite volleyball players and to observe the influence of eightweeks of stabilization exercise on the TrA. Method: 10 female elitevolleyball players (mean age 24,7 years, range 18-31 years) participated inthe study. TrA was measured in supine position with a pressure biofeedbackunit. Subjects were instructed to draw in the abdominal wall without movingthe pelvis and hold for 10 seconds.
Entrepreneurs subjective well-being and job satisfaction: does personality matter?
Previous research has suggested that there is a strong and positive relationship between being an entrepreneur and possessing a high degree of subjective well-being as well as job satisfaction. The big five personality traits have also been argued to be significantly related to both subjective well-being and job satisfaction. Little is however known if personality affects entrepreneurs and regular employees differently. In this paper the impact of personality traits on the cognitive part of subjective well-being as well as job satisfaction are investigated separately among entrepreneurs and regular employees. This is done through OLS-regressions using a Swedish nationally representative survey Employment, Material Resources, and Political Preferences (EMRAPP), where entrepreneurs were oversampled in order to be able to compare entrepreneurs (N = 2483) and regular employees (N = 2642).
Avbrottsfri Kraft med användning av ultrakondensatorer
The supply of uninterruptible power can be applied to many areas wherecontinuous operation is highly prioritized.The application of uninterruptible power for motor operation is facilitatedusing a frequency converter. Direct current operated frequency converters canbe applied directly to the power reserve which removes the need for additionalpower-converting.Batteries have long constituted the power reserve but advancements inthe development of ultracapacitors have created a viable substitution. Ultra-capacitors have high energy storing capabilities and can be applied to highpower applications.Maxwell is a leading manufacturing company of ultracapacitors and pro-vide different modules with built-in solutions for voltage balancing. Unevenvoltages between series-connected capacitors is a phenomenon caused by vary-ing capacitance. A configuration containing Maxwell?s 56V module is createdand constitutes the power reserve in the simulations.The discharge simulation shows a significant current that could damagethe system.
Studenters riskuppfattning och beredskap i hemmet : En kvalitativ studie om kopplingen mellan riskuppfattning och beredskap i hemmet
The focus of this thesis is on what is considered to be a suitable foster home. For the study to be carried out an application had to be made to get access to the foster home assessments in a medium-sized municipality in Sweden. With the support of attachment theory and theory of standards different categories have been picked out and analyzed in foster home assessements that have been approved. The conclusion to what is considered to be a suitable foster home is a complex issue, as there are many factors that are interacting. Social workers seem to focus on the importance of a family?s ability to provide some kind of stability and security for a child who is considered to be placed within their home.
Säkerhetsanalys av brandbekämpning i kritiska utrymmen på Forsmark 1
In order to maintain a high safety level at a nuclear power plant it is important not only to measure the reliability of the components and systems of the plant, but also to investigate how the plant responds to human actions. One of the most hazardous situations in managing a power plant is fire occurring in critical areas. This study concerns the prospect of the local fire brigade to suppress a fire that has started in one of the most critical rooms for maintaining high reactor safety. The model created gives an indication on the possibilities of succeeding in suppressing a fire. In order to get a more reliable fire fighting the following advice are given:- Let the fire brigade go rounds in the plant together with the personnel, during which recommended fire suppressing methods are determined to avoid long preparation time in an actual situation.- Prepare rooms with two subsystems to make them partly with no voltage.- Give the fire brigade better feedback from actual events on nuclear power plants.- Education and training in suppressing fires in electrical equipment.The probabilistic safety assessment strives to be as realistic as possible.
PSQS ? Power Supply Quality Simulator
Kitron had wishes to be able to test and measure how disturbance affects their vehicle electronic units before they have been verified by SP Technical Research Institute of Sweden in Borås. This work started with the writing of a demand specification together with Kitron for a product PSQS, Power Supply Quality Simulator, which can generate some test pulses according to a standard for electronic units to Volvos vehicles. A design proposal was developed with the help the demand specification and was verified with the help of simulations. All electric schematics was designed with the guide of the design proposal. The pulses realized in the works of this thesis are those which Kitron experienced that they have a need to test in their own premises and which are possible to generate with the means available.
Hur svårt kan det va?: En studie om kreativitet i arbetet med Melodifestivalen
The swedish song contest ?Melodifestivalen? is the most popular TV-show in Sweden according to number of viewers. Not only has it managed to remain the viewers? number-one choice year after year, it has also engaged a lot of the viewers (2, 4 millions in this year?s final) to vote for their favourite song. Melodifestivalen is classified as a creative organisation since it has evident elements of creativity in its process, product and among its employees.
Integritet och långsiktig användbarhet hos textdokument : En avvägningsproblematik vid digitalt bevarande
This thesis is about a potential trade-off between integrity and long-term usability in the choice of file formats for preservation of text documents. Five common formats are discussed: plain text, PDF/A, Office Open XML Document, Open Document Text, and Markdown. The formats are compared with respect to four criteria related to integrity and usability and to the records continuum model: support by widely used software, stability, rendering of contents and reusability.It is concluded that no single format is optimal with respect to all four criteria, when it comes to preserving typical documents in a modern environment, with more or less complex formatting and document structure. Therefore, the feasiblity of using two or more formats for preservation of a single document (e.g. PDF/A combined with Markdown and/or Office Open XML) is discussed.
Kan coreträning påverka upplevelsen av smärta i nacke, axlar och skuldor? : Fyra veckors hemträning med övningen "plankan"
Syfte och frågeställningar Studiens syfte var att undersöka om utförandet av en isometrisk bålstabiliseringsövning/coreövning kunde påverka upplevelsen av smärta i nacke, axlar och skuldror hos kvinnor med kronisk/långvarig idiopatisk smärta. Studiens frågeställningar var: Hur påverkar utförandet av övningen ?plankan? upplevelsen av smärta i nacke, axlar och skuldror hos deltagarna? Förändras den maximala uthålligheten i övningen mellan deltagarnas första och sista träningstillfälle? Kan interventionen fullföljas av deltagarna?Metod Fyra kvinnliga deltagare som alla hade kronisk/långvarig smärta i nacke, axlar eller skuldror utförde övningen ?plankan? som hemträningsövning under fyra veckors tid. Mängden träning dokumenterades i en träningsdagbok som deltagarna kontinuerligt fyllde i under träningsperioden. Före samt inom en vecka efter träningsperioden ifylldes en enkät med frågor om upplevd intensitet, frekvens och lokalisation av smärta.
Spänningsfall i 200 V 400 Hz system
Målet med examensarbetet har varit att ta fram teoretiskt underlag och en beräkningsmodell. Detta ska beskriva hur kabeltyp, kabellängd, kabelarea samt effektfaktor påverkar spänningsfallet över ett 400 Hz ledningssystem.Mätningar har utförts på två olika kablar som används i det aktuella systemet. En av kablarna var symmetriskt uppbyggd med 7 ledare, där respektive fas bestod av två ledare förskjutna 180° från varandra runt nolledaren. För att åstadkomma 115/200V 400 Hz, användes en 90 kVA frekvensomformare. Belastningen som användes var en resistiv, induktiv samt en kapacitiv belastning.
Numerisk simulering av jordtryck mot rörbro ? Med tillämpning av programmet PLAXIS
This thesis deals with numerical simulation of earth pressure against tubular bridges in the software Plaxis. Plaxis is a FEM (Finite Element Method) software based on numerical calculations for which approximate solutions are developed through an iterative process. The program is specifically designed for soil and rock mechanical tests, such as voltage and deformation calculations in soil.The Royal Institute of Technology conducted in 2005, field tests on tubular bridges of corrugated steel, which was part of Ersa Bayoglu Fleners PhD (Bayoglu Flener, 2009). She studied how two different tubular bridges deformed during installation and filling. Tests and measurements were made during filling.
Thembalabantwana ?Hope for our children? ? A study about Social Workers work with children who are orphaned because of HIV/Aids in South Africa.
The purpose of our thesis has been to study Social Workers view of children?s needs and how they work with children?s needs when they are orphaned because of HIV/Aids in South Africa. The question formulations we used to answer our purpose are:? What needs do the Social Workers consider the children to have?? How do the Social Workers work with children?s needs?We have a qualitative methodological approach in the thesis, where we have performed four interviews with four Social Workers on different organizations in and around Cape Town, South Africa. The presentation of the empirics is made as a summary with representative quotations, which we have interweaved with earlier research and theoretical conceptions.
Parental experiences when children are undergoing emergency surgery/Föräldrars upplevelser i samband med att deras barn genomgår en akut operation
When a child is hospitalized, it is usually more than one person who needs attention ? i.e. the child as well as its parents. The emergency ward environment and surgery rooms are unfamiliar and the parents feel anxious, insecure and uncertain about how to act. They are expected to participate in the child?s care, cope with their own anxiety and simultaneously convey a sense of security and stability to the child.
Uppgradering av stabilitetsberäkningsprogrammet NYSTAB
This is a report founded on a project by Atlas Copco called NYSTAB. The application Nystab is a calculation program that can calculate the stability of the rockdrill-rigs made by Atlas Copco. The original version of Nystab is stored in a database from 1997 and the code is made in an old version of Visual Basic. My assignment was to develop the application in to a newer programming environment and make it last better in the upcoming years. The software I decided to use to accomplish this project is C# .NET in Visual Studio and Microsoft Access 2010. All the code is written in C# with some insertions from ADO.NET which helped me to easier connect the code with the database.The coding part was split into two pieces; the first was to develop the application scale done with Windows Forms, the second was to write the code for calculations in the application.