During the last two decades, the increase in electricity demand and environmental concern resulted in fast growth of power production from renewable sources. Wind power is one of the most efficient alternatives. Due to the rapid development of wind turbine technology and increasing size of wind farms, wind power plays a significant part in the power production mix of Germany, Spain, Denmark, and some other countries. The best conditions for the development of wind farms are in remote, open areas with low population density. The transmission system in such areas might not be dimensioned to accommodate additional large-scale power infeed. Furthermore a part of the existing transmission capacity might already be reserved for conventional power plants situated in the same area. In this thesis four alternatives for large-scale wind power integration in areas with transmission bottlenecks are considered. The first possibility is to revise the methods for calculation of available transmission capacity. The second solution for large-scale integration of wind power in such areas is to reinforce the network. This alternative, however, may be expensive and time consuming. As wind power production depends on the wind speed, the full load hours of wind turbine generator are only 2000-4000 hours per year. Therefore reinforcing a transmission network in order to remove a bottleneck completely is often not economically justified. Wind energy curtailments during congestion situations is then the third solution for large-scale wind power integration with less or no grid reinforcement. The fourth solution is to store excess wind energy. Pumped hydro storage or battery storage for the large-scale wind farms are still rather expensive options, but existing conventional power plants with fast production control capabilities and sufficient storage capacity, e.g., hydro power plants, could be used for this purpose. As there is a lot of research work on the first two alternatives, the thesis provides a review and summarizes the main conclusions from the existing work. The thesis is then directed towards the development of the methods for estimation of wind energy curtailments, evaluation of wind energy storage possibility in hydro reservoirs and development of short term hydro power production planning methods, considering coordination with wind power. Additionally in the thesis the strategy that minimizes imbalance costs of a wind power utility, trading wind power on the short term power market is elaborated and analyzed. / QC 20100608

The presence of partial discharges (PD) in high voltage components is generally a sign of defects and degradation in the electrical insulation. To diagnose the condition of high voltage insulation, PD measurements is commonly used. The Variable Frequency Phase Resolved PD Analysis (VF-PRPDA) technique measures PD at variable frequency of the applied voltage. With this technique, the frequency dependence of PD can be utilized to extract more information about the insulation defects than is possible from traditional PD measurements at a single applied frequency. In this thesis the PD process in a disc-shaped cavity is measured and modelled at variable frequency (0.01 - 100 Hz) of the applied voltage. The aim is to interpret the PD frequency dependence in terms of physical conditions at the cavity. The measurements show that the PD process in the cavity is frequency dependent. The PD phase and magnitude distributions, as well as the number of PDs per voltage cycle, change with the varying frequency. Moreover, the PD frequency dependence changes with the applied voltage amplitude, the size of the cavity and the location of the cavity (insulated or electrode bounded). A physical model is presented and used to dynamically simulate the sequence of PDs in the cavity at different applied frequencies. The simulations show that essential features in the measured PD patterns can be reproduced. The PD frequency dependence is interpreted as a variation in influence on the PD activity from the statistical time lag of PD and the charge transport in the cavity surface, at different applied frequencies. The simulation results also show that certain cavity parameters, like the cavity surface conductivity and the rate of electron emission from the cavity surface, change with the time between consecutive PDs, and accordingly with the applied frequency. This effect also contributes to the PD frequency dependence. / QC 20100722

Maintenance optimisation is essential to achieve cost-efficiency, availability and reliability of supply in electric power systems. The process of maintenance optimisation requires information about the costs of preventive and corrective maintenance, as well as the costs of failures borne by both electricity suppliers and customers. To calculate expected costs, information is needed about equipment reliability characteristics and the way in which maintenance affects equipment reliability. The aim of this Ph.D. work has been to develop equipment reliability models taking the effect of maintenance into account. The research has focussed on the interrelated areas of condition estimation, reliability modelling and maintenance modelling, which have been investigated in a number of case studies. In the area of condition estimation two methods to quantitatively estimate the condition of disconnector contacts have been developed, which utilise results from infrared thermography inspections and contact resistance measurements. The accuracy of these methods were investigated in two case studies. Reliability models have been developed and implemented for SF6 circuit-breakers, disconnector contacts and XLPE cables in three separate case studies. These models were formulated using both empirical and physical modelling approaches. To improve confidence in such models a Bayesian statistical method incorporating information from the equipment design process was also developed. This method was illustrated in a case study of SF6 circuit-breaker operating rods. Methods for quantifying the effect of maintenance on equipment condition and reliability have been investigated in case studies on disconnector contacts and SF6 circuit-breakers. The input required by these methods are condition measurements and historical failure and maintenance data, respectively. This research has demonstrated that the effect of maintenance on power system equipment may be quantified using available data. However, realising the full potential of these methods requires the gathering and utilisation of failure and maintenance data as well as condition measurements to be improved. / QC 20100823

The dissertation deals with an account of actual problem, which can arise within EMC and power quality. The cause of power interruption and what can be done to minimise the power interruption is discussed. It also includes a definition of planning levels and which factors one needs to have control over to carry out a possible planning strategy and how the local distributions net could be more secure. The electrical net could be secure but no system can be free from interruption. The dissertation examines two distribution transformers: GLA40T1 (Glansås) and T399 in Tranås Energy which don’t have regulators. It applies a planning level for voltage variation in the voltage of second level with +/-5 % of nominal voltage. The purpose is to reduce the consequence of high voltage variation and to keep the costs at an acceptable level. The research also makes even clear the similarity between results of the theoretical calculations and results of the practical measurements taken from Tranås Energy. The examination shows that the supposed planning level is fulfilled. / Examensarbetet behandlar de faktiska problem som kan uppstå inom EMC (Electro Magnetic Compatibility) och el-kvalité, orsaken till elavbrott diskuteras och vad som kan göras för att minimera avbrotten. Arbetet innehåller också en definition av planeringsnivåer och vilka faktorer man behöver ha kontroll över för att genomföra ett eventuellt planeringsutrymme, och hur lokala distributionsnät kan bli säkrare. Näten kan bli säkrare men inget system kan bli avbrottsfritt. I examensarbetet undersöks två fördelningstransformatorer: GLA40T1(Glansås) och T399 i Tranås energi. Båda transformatorerna saknar regulator. Man tillämpar en planeringsnivå för spänningsvariationen på spänningen på sekundära sidan som är +/-5 % av nominell spänning. Avsikten är att minska konsekvenserna av höga spänningsvariationer och att hålla kostnaden på en acceptabel nivå. Undersökningen omfattar också en jämförelse mellan de teoretiska beräkningsresultaten och de verkliga mätningarna som är hämtade från Tranås energi. Undersökningen visar att antagna planeringsnivån är uppfyllda

No description available.

OKG AB äger de tre kokvattenreaktorerna Oskarshamn 1, 2 och 3. Kärnkraftverket ligger i Simpevarp norr om Oskarshamn. Examensarbetet har utförts på Oskarshamn 1 inom ett projekt som kallas CEM. Oskarshamn 1 togs i drift 1972 och kan leverera en elektrisk effekt på 491 MW. Examensarbetet behandlar underhållsaspekter som bör tas hänsyn till vid projektering och konstruktion av det nya automatiskt gasturbinsäkrade 6,3 kV ställverket i system 642. Ställverket är huvudfördelningsställverk inom Oskarshamn 1 och ska bytas ut på grund av hög ålder samt brist på reservdelar. I syfte att uppnå hög driftsäkerhet och tillgänglighet för det nya ställverket har aspekter som förbättrar dess funktionssäkerhet, underhållsmässighet och underhållssäkerhet specificerats. Förslag på ny lastfördelning samt uppställning av ställverkets fack ges också. Resultatet av examensarbetet är de framtagna underhållsaspekter som kan tillämpas vid projektering och konstruktion av ställverket. De viktigaste underhållsaspekterna som tagits fram är att utrustningen ska vara personsäker, det ska finnas tillräckligt med utrymme i facken för att kunna utföra underhållsarbete samt att fullständig dokumentation ska levereras samtidigt som utrustningen. Ett förslag till ny lastfördelning av ställverkets belastningar har utförts utifrån en teknisk specifikation. Förslaget på uppställning av ställverkets fack tyder på att tillräckligt utrymme finns i befintliga ställverksrum. / OKG AB is the owner of the three boiling water reactors Oskarshamn 1, 2 and 3. The nuclear power plant is located in Simpevarp north of Oskarshamn. The thesis has been carried out at Oskarshamn 1 within a project called CEM. Oskarshamn 1 started to produce electricity in 1972 and can today deliver an electrical power of 491 MW. The thesis considers maintenance aspects which are to be taken into consideration before planning and construction of the new automatic gas turbine secured switchgears in system 642. The switchgears are the main distribution switchgears within Oskarshamn 1 and are to be replaced because of high age and lack of spare parts. In purpose to achieve high availability performance and availability for the switchgears, aspects which improves the reliability, maintainability and maintenance supportability has been specified. Suggestion of new distribution of the loads between the busbars and arrangement of the cubicles has also been carried out and specified. The results of the thesis are the specified maintenance aspects which can be used when planning and constructing the switchgears. The most important maintenance aspects are that the equipment has high personnel safety, that there is enough space in the cubicles to perform maintenance and that a complete documentation is delivered together with the equipment. Suggestion of new load distribution between the busbars has been carried out with the help of a technical specification. The suggestion of new arrangement for the switchgears implies that there is enough space in the existing electrical room for the switchgears.

<p>Detta examensarbete beskriver hur en Monte Carlo simulering (MCS) kan användas för tillförlitlighetsanalys av ett eldistributionssystem. Metoden har implementerats i verktyget RADPOW som nu kan utföra både analytiska och numeriska beräkningar. Angreppssättet för att utveckla denna MCS metod i RADPOW innefattade följande aktiviteter:</p><p>• Vidareutvecklade av RADPOW med införandet av ett grafiskt användargränssnitt för Windows.</p><p>• Utveckling och implementering av en iterativ analytisk metod för känslighetsanalys av eldistributionssystem i RADPOW.</p><p>• Utveckling och implementering av MCS metoden i RADPOW, vilken placerades i en fristående modul kallad Sim.</p><p>Den implementerade MCS metoden har validerats i en jämförande studie innefattande två testsystem med datorprogrammet NEPLAN. Resultat från denna studie visar att MCS metoden ger samma resultat som den analytiska metoden i RADPOW och det kommersiella verktyget NEPLAN.</p> / <p>This master thesis describes an implementation of a Monte Carlo Simulation (MCS) method for reliability assessment of electrical distribution systems. The method has been implemented in the reliability assessment tool RADPOW which now is able to perform both analytical and simulation evaluations. The main contributions within this thesis includes the following activities;</p><p>• Further development of RADPOW by the introducing of a graphical user interface for Windows.</p><p>• Development and implementation of an analytical sensitivity analysis routine for RADPOW.</p><p>• Development and implementation of a sequential MCS method in RADPOW in a stand alone module referred to as Sim.</p><p>The implemented MCS method has been validated in a comparable study for two case systems by a commercial software NEPLAN. Results shows that the implemented MCS method provides the same results as the analytical method in RADPOW and the NEPLAN software.</p>

<p>The dissertation deals with an account of actual problem, which can arise within EMC and power quality. The cause of power interruption and what can be done to minimise the power interruption is discussed. It also includes a definition of planning levels and which factors one needs to have control over to carry out a possible planning strategy and how the local distributions net could be more secure. The electrical net could be secure but no system can be free from interruption.</p><p>The dissertation examines two distribution transformers: GLA40T1 (Glansås) and T399 in Tranås Energy which don’t have regulators. It applies a planning level for voltage variation in the voltage of second level with +/-5 % of nominal voltage. The purpose is to reduce the consequence of high voltage variation and to keep the costs at an acceptable level. The research also makes even clear the similarity between results of the theoretical calculations and results of the practical measurements taken from Tranås Energy. The examination shows that the supposed planning level is fulfilled.</p> / <p>Examensarbetet behandlar de faktiska problem som kan uppstå inom EMC (Electro Magnetic Compatibility) och el-kvalité, orsaken till elavbrott diskuteras och vad som kan göras för att minimera avbrotten. Arbetet innehåller också en definition av planeringsnivåer och vilka faktorer man behöver ha kontroll över för att genomföra ett eventuellt planeringsutrymme, och hur lokala distributionsnät kan bli säkrare. Näten kan bli säkrare men inget system kan bli avbrottsfritt.</p><p>I examensarbetet undersöks två fördelningstransformatorer: GLA40T1(Glansås) och T399 i Tranås energi. Båda transformatorerna saknar regulator. Man tillämpar en planeringsnivå för spänningsvariationen på spänningen på sekundära sidan som är +/-5 % av nominell spänning. Avsikten är att minska konsekvenserna av höga spänningsvariationer och att hålla kostnaden på en acceptabel nivå. Undersökningen omfattar också en jämförelse mellan de teoretiska beräkningsresultaten och de verkliga mätningarna som är hämtade från Tranås energi. Undersökningen visar att antagna planeringsnivån är uppfyllda</p>

No description available.

Dynamic security limits the power transfer capacity between regions and therefore has an economic impact. The power modulation control of high-voltage direct current (HVDC) links can improve the dynamic security of the power system. Having several HVDC links in a system creates the opportunity to coordinate such control, and coordination also ensures that negative interactions do not occur among the controllable devices. This thesis aims to increase dynamic security by coordinating HVDC links, as an alternative to decreasing the transfer capacity. This thesis contributes four control approaches for increasing the dynamic stability, based on feedforward control, adaptive control, optimal control, and exact-feedback linearization control. Depending on the available measurements, dynamic system model, and system topology, one of the developed methods can be applied. The wide-area measurement system provides the central controller with real-time data and sends control signals to the HVDC links. The feedforward controller applies rapid power dispatch, and the strategy used here is to link the N-1 criterion between two systems. The adaptive controller uses the modal analysis approach; based on forecasted load paths, the controller gains are adaptively adjusted to maximize the damping in the system. The optimal controller is designed based on an estimated reduced-order model; system identification develops the model based on the system response. The exact-feedback linearization approach uses a pre-feedback loop to cancel the nonlinearities; a stabilizing controller is designed for the remaining linear system. The conclusion is that coordinating the HVDC links improves the dynamic stability, which makes it possible to increase the transfer capacity. This conclusion is also supported by simulations of each control approach. / QC 20110302