<p>Power system simulations, power market analysis as well as power system security and reliability analysis now serves as fundamental analysis tasks in power system planning and operation. Thus, it is very useful to discuss techniques, data needs and methodologies related power system reliability. Work is very important both in terms of operational and economical aspects of a modern power system. The task of determining the reliability of a given power system can be a complex and difficult process. Several methodologies exist and the terminology describing these calculations may differ from case to case. The work performed in this thesis demonstrates a known reliability methodology related to a real-life power system. In the latter, PSS®SINCAL and its reliability module ZUBER has been emphasized. The development of a working test model has been an important part of this thesis. In the latter, statistical information describing the power system has been the main challenge, both in terms of availability and quality. The various reliability data have been calculated from annual failure statistics collected by Statnett and experience data from Siemens. The scope of the reliability analysis was to determine the affect of future load expansions. It is a known fact that load development can affect the reliability of the power system and potentially increase the frequency of supply interruptions causing higher CENS costs. However, this was not the case as the changes in frequency of supply interruptions were insignificant. The results showed a suspected CENS cost increase of 1.6 NOK. Thus, it is evident that this is due to the fact that the uninterrupted power is now substantially larger. The reliability analysis show that the given power system will sustain its high level of reliability even with the planned load expansion. A comparative analysis of the ongoing development of a methodology (SAMREL) incorporating power market analysis via power flow and contingency analysis and PSS®SINCAL have also been presented. Comparing tools describing probabilistic reliability are important and can act as an incentive for future development of reliability tools. The major strength of PSS®SINCAL compared to SAMREL is simply the fact that PSS®SINCAL is a developed and commercialized tool. Unfortunately it was not possible conduct a reliability analysis using SAMREL, which was a major draw-back as a comparative analysis of both the tools relates to the same test model would have been very beneficial. SAMREL is comprised of several existing tools and therefore rely on the interaction between these tools, which after my opinion further complicate both the user friendliness and process of commercialization. From an educational point-of-view, the work related to SAMREL has several benefits contributing to increased general knowledge about power system reliability. It is evident that the accuracy of any reliability analysis depends on the quality of the statistical data. The studies show that local statistical data e.g. data based on local knowledge or local statistics often pose as a better solution. However, such data are unfortunately often very difficult to obtain, leaving no alternative as to use the available more general data. However, it is evident that some uncertainties always will exist but need to be taken into consideration when conducting such analysis. However, close cooperation with the utilities in combination with the utilization of high quality reliability data will after my opinion have a positive affect on the accuracy of the reliability analysis. Another important subject related to reliability is the process of identifying the critical system components. As shown, the main tool presented in this thesis is the consequence matrix, which categories the results obtained from the reliability analysis. The categories indicate both the consequence and the corresponding probability. Such matrixes need to be the result of a joint effort from both the customer and the professionals performing the criticality analysis, including all relevant information needed to classify criticality. The strength of this method lies in the fact that the defined probabilities can be used to identify large elements, such as substations and then be further utilized on a component level for the critical substation. The methodologies describing power system reliability have been emphasized throughout this thesis. The given test system and the performed reliability calculation demonstrates PSS®SINCAL as a tool for determining the reliability of a power system. The methodology utilized in this report is from the author’s point of view a good representation of a state of the art reliability analysis.</p>

<p>In the last decades, due to the environmental concerns and the increase of energy demand, wind power has strongly penetrated the field of electricity generation. Today, because of the lack of onshore sites and visual and noise nuisances, the development of wind farms turns more and more to offshore and Norway has a great potential of offshore wind power. This thesis investigates the impact of the integration of an offshore 1000MW wind farm on the Norwegian power system. Two different transmissions are used, one HVAC transmission system and one HVDC transmission system. They are installed in four different configurations which represent the possible cases of wind farm integration regarding the distance from the shore. Two different connection points have been chosen regarding the load flow simulations. The first one is situated in the region of Bergen in the West Norway and the other one is situated between Kristiansand and Stavanger in the south Norway. In order to investigate the power stability and the behaviour of the system, simulations are performed under both steady-state and dynamic conditions by using PSSTME. Disturbances are applied in different locations on the system both near the connection point and on the offshore wind farm. The results show that the power system with large offshore wind power remains stable after the different faults. The requirements of the Norwegian Transmission System Operator, Statnett, are respected after the integration of a large offshore wind farm in the Norwegian power system.</p>

<p>A stable and reliable electric power supply system is an inevitable pre-requisite for the technological and economic growth of any nation. Due to this, utilities must strive and ensure that the customer’s reliability requirements are met and the regulators requirements satisfied at the lowest possible cost. It is known fact around the world that 90% of the of the customer service interruptions are caused due to failure in distribution system. Therefore, it is worth considering reliability worth assessments as it provides an opportunity to incorporate the cost or losses incurred by the utilities customer as a result of power failure and this must be considered in planning and operating practices. The system modeling and simulation study is carried out on one of the district’s distribution system which consists of 33kV and 11kV network in Bhutan. The reliability assessment is done on both 11 and 33kV system to assess the performance of the present system and also predictive reliability analysis for the future system considering load growth and system expansion. The alternative which gives low SAIDI, SAIFI and minimum breakeven costs are being assessed and considered. The reliability of 33kV system could be further improved by installation of load break switch, auto recloser and connecting with line coming from other district (reserve) at reasonable break even cost. The decision base could be further improved by having Bhutan’s context interruption cost. However, the questionnaire’s which may be used in Bhutan to acquire interruption costs from the customers are being proposed. The utility should have their own reliability improvement strategy depending upon their needs and requirements of the regulators. Although there is no magic bullet in managing power quality issues, utilities can maximize network performance and better serve customers by diligently addressing trouble prone areas. In order to achieve this objective, a computer program NetBas/Lesvik is used to run load flow and reliability analysis, thus selecting the alternatives either based on reliability indices or on cost benefit ratio.</p>

<p>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.</p>

<p>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.</p>

<p>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.</p>

<p>Healthcare organizations need to handle many kinds of information and integrate different support systems, which may be accessed from external corporations. Service Oriented Architecture (SOA) provides the means to achieve a common platform to deploy services that can be used across the organization and its boundaries, but introduces new security concerns that need to be evaluated in order to implement a secure system, while still suffering from standard threats. Web Services are the common way to implement SOA applications, having several standards related to security (such as XML Encryption, XML Signature and WS-Security). Still, other security mechanisms such as input validation and SSL/TLS need to be thought of as well. A penetration test based on recognized methodologies and guidelines, such as the NIST Technical Guide to Information Security Testing and Assessment, OWASP Testing Guide and SIFT Web Services Security Testing Framework, was performed on a case study system. A proof of concept application making use of a set of middleware (web) services, the MPOWER platform, was audited in order to expose vulnerabilities. After conducting the penetration test on the system, 10 out of 15 scenarios presented security issues. The vulnerabilities found were described, demonstrating several risks from misusing, or not implementing at all, security mechanisms. As a consequence, countermeasures and recommendations were proposed in an attempt to improve the overall security of SOA-based (healthcare) systems. The results of the assessment show us how important is to validate the security of a system before putting it into production environment. We also come to the conclusion that security testing should be an inherent part of a secure software development life cycle. Moreover, not only healthcare systems may benefit from this study, and also not only SOA-based ones.</p>

<p>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%.</p>

<p>Unsolicited bulk email, commonly known as spam, represents a significant problem on the Internet. The seriousness of the situation is reflected by the fact that approximately 97% of the total e-mail traffic currently (2009) is spam. To fight this problem, various anti-spam methods have been proposed and are implemented to filter out spam before it gets delivered to recipients, but none of these methods are entirely satisfactory. This thesis analyzes the properties of spam filters from the viewpoint of Signal Detection Theory (SDT). The Bayesian approach of Signal Detection Theory provides a basis for determining the tuning of spam filters from the particular user's point of view and helps in determining the utility which the spam filter provides to the user.</p>

<p>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.</p>