Bulk electric system reliability analysis is an important activity in both vertically integrated and unbundled electric power utilities. Competition and uncertainty in the new deregulated electric utility industry are serious concerns. New planning criteria with broader engineering consideration of transmission access and consistent risk assessment must be explicitly addressed. Modern developments in high speed computation facilities now permit the realistic utilization of sequential Monte Carlo simulation technique in practical bulk electric system reliability assessment resulting in a more complete understanding of bulk electric system risks and associated uncertainties. Two significant advantages when utilizing sequential simulation are the ability to obtain accurate frequency and duration indices, and the opportunity to synthesize reliability index probability distributions which describe the annual index variability. <p>This research work introduces the concept of applying reliability index probability distributions to assess bulk electric system risk. Bulk electric system reliability performance index probability distributions are used as integral elements in a performance based regulation (PBR) mechanism. An appreciation of the annual variability of the reliability performance indices can assist power engineers and risk managers to manage and control future potential risks under a PBR reward/penalty structure. There is growing interest in combining deterministic considerations with probabilistic assessment in order to evaluate the system well-being of bulk electric systems and to evaluate the likelihood, not only of entering a complete failure state, but also the likelihood of being very close to trouble. The system well-being concept presented in this thesis is a probabilistic framework that incorporates the accepted deterministic N-1 security criterion, and provides valuable information on what the degree of the system vulnerability might be under a particular system condition using a quantitative interpretation of the degree of system security and insecurity. An overall reliability analysis framework considering both adequacy and security perspectives is proposed using system well-being analysis and traditional adequacy assessment. The system planning process using combined adequacy and security considerations offers an additional reliability-based dimension. Sequential Monte Carlo simulation is also ideally suited to the analysis of intermittent generating resources such as wind energy conversion systems (WECS) as its framework can incorporate the chronological characteristics of wind. The reliability impacts of wind power in a bulk electric system are examined in this thesis. Transmission reinforcement planning associated with large-scale WECS and the utilization of reliability cost/worth analysis in the examination of reinforcement alternatives are also illustrated.

<p>The weather environment has a significant impact on the reliability of a power system due to its effect on the system failure mechanisms of overhead circuits and on the operational ability of an electric power utility. The physical stresses created by weather increase the failure rates of transmission or distribution lines operating in adverse weather conditions, resulting in increased coincident failures of multiple circuits. Exceptionally severe weather can cause immense system damages and significantly impact the reliability performance. Recognition of the pertinent weather impacts clearly indicates the need to develop appropriate models and techniques that incorporate variable weather conditions for realistic estimation of reliability indices.</p> <p>This thesis illustrates a series of multi-state weather models that can be utilized for predictive reliability assessment incorporating adverse and extremely adverse weather conditions. The studies described in this thesis are mainly focused on the analyses using the three state weather model. A series of multi-state weather models are developed and utilized to assess reliability performance of parallel redundant configurations. The application of weather modeling in reliability evaluation is illustrated using a practical transmission system. The thesis presents an approach to identify weather specific contributions to system reliability indices and illustrates the technique by utilizing a test distribution system. The analysis of a range of reliability distributions with regard to major event day segmentation is presented.</p><p>The research work illustrated in this thesis clearly illustrates that reliability indices estimated without recognition of weather situations are unrealistic and that at minimum the three state weather model should be applied in reliability evaluation of systems residing in varying weather environments. The conclusions, concepts and techniques presented in this thesis should prove useful in practical application.</p>

Bulk electric system reliability analysis is an important activity in both vertically integrated and unbundled electric power utilities. Competition and uncertainty in the new deregulated electric utility industry are serious concerns. New planning criteria with broader engineering consideration of transmission access and consistent risk assessment must be explicitly addressed. Modern developments in high speed computation facilities now permit the realistic utilization of sequential Monte Carlo simulation technique in practical bulk electric system reliability assessment resulting in a more complete understanding of bulk electric system risks and associated uncertainties. Two significant advantages when utilizing sequential simulation are the ability to obtain accurate frequency and duration indices, and the opportunity to synthesize reliability index probability distributions which describe the annual index variability. <p>This research work introduces the concept of applying reliability index probability distributions to assess bulk electric system risk. Bulk electric system reliability performance index probability distributions are used as integral elements in a performance based regulation (PBR) mechanism. An appreciation of the annual variability of the reliability performance indices can assist power engineers and risk managers to manage and control future potential risks under a PBR reward/penalty structure. There is growing interest in combining deterministic considerations with probabilistic assessment in order to evaluate the system well-being of bulk electric systems and to evaluate the likelihood, not only of entering a complete failure state, but also the likelihood of being very close to trouble. The system well-being concept presented in this thesis is a probabilistic framework that incorporates the accepted deterministic N-1 security criterion, and provides valuable information on what the degree of the system vulnerability might be under a particular system condition using a quantitative interpretation of the degree of system security and insecurity. An overall reliability analysis framework considering both adequacy and security perspectives is proposed using system well-being analysis and traditional adequacy assessment. The system planning process using combined adequacy and security considerations offers an additional reliability-based dimension. Sequential Monte Carlo simulation is also ideally suited to the analysis of intermittent generating resources such as wind energy conversion systems (WECS) as its framework can incorporate the chronological characteristics of wind. The reliability impacts of wind power in a bulk electric system are examined in this thesis. Transmission reinforcement planning associated with large-scale WECS and the utilization of reliability cost/worth analysis in the examination of reinforcement alternatives are also illustrated.

Electric power systems are experiencing dramatic changes with respect to structure, operation and regulation and are facing increasing pressure due to environmental and societal constraints. Bulk electric system reliability is an important consideration in power system planning, design and operation particularly in the new competitive environment. A wide range of methods have been developed to perform bulk electric system reliability evaluation. Theoretically, sequential Monte Carlo simulation can include all aspects and contingencies in a power system and can be used to produce an informative set of reliability indices. It has become a practical and viable tool for large system reliability assessment technique due to the development of computing power and is used in the studies described in this thesis. The well-being approach used in this research provides the opportunity to integrate an accepted deterministic criterion into a probabilistic framework. This research work includes the investigation of important factors that impact bulk electric system adequacy evaluation and security constrained adequacy assessment using the well-being analysis framework.<p> Load forecast uncertainty is an important consideration in an electrical power system. This research includes load forecast uncertainty considerations in bulk electric system reliability assessment and the effects on system, load point and well-being indices and reliability index probability distributions are examined. There has been increasing worldwide interest in the utilization of wind power as a renewable energy source over the last two decades due to enhanced public awareness of the environment. Increasing penetration of wind power has significant impacts on power system reliability, and security analyses become more uncertain due to the unpredictable nature of wind power. The effects of wind power additions in generating and bulk electric system reliability assessment considering site wind speed correlations and the interactive effects of wind power and load forecast uncertainty on system reliability are examined. The concept of the security cost associated with operating in the marginal state in the well-being framework is incorporated in the economic analyses associated with system expansion planning including wind power and load forecast uncertainty. Overall reliability cost/worth analyses including security cost concepts are applied to select an optimal wind power injection strategy in a bulk electric system. The effects of the various demand side management measures on system reliability are illustrated using the system, load point, and well-being indices, and the reliability index probability distributions. The reliability effects of demand side management procedures in a bulk electric system including wind power and load forecast uncertainty considerations are also investigated. The system reliability effects due to specific demand side management programs are quantified and examined in terms of their reliability benefits.

Due to power system deregulations, transmission expansion not keeping up with the load growth, and higher frequency of natural hazards resulting from climate change, major blackouts are becoming more frequent and are spreading over larger regions, entailing higher losses and costs to the economy and the society of many countries in the world. Large-scale blackouts typically result from cascading failure originating from a local event, as typified by the 2003 U.S.-Canada blackout. Their mitigation in power system planning calls for the development of methods and algorithms that assess the risk of cascading failures due to relay over-tripping, short-circuits induced by overgrown vegetation, voltage sags, line and transformer overloading, transient instabilities, voltage collapse, to cite a few. How to control the economic losses of blackouts is gaining a lot of attention among power researchers. In this research work, we develop new Monte Carlo methods and algorithms that assess and manage the risk of cascading failure in composite reliability of deregulated power systems. To reduce the large computational burden involved by the simulations, we make use of importance sampling techniques utilizing the Weibull distribution when modeling power generator outages. Another computing time reduction is achieved by applying importance sampling together with antithetic variates. It is shown that both methods noticeably reduce the number of samples that need to be investigated while maintaining the accuracy of the results at a desirable level. With the advent of microgrids, the assessment of their benefits in power systems is becoming a prominent research topic. In this research work, we investigate their potential positive impact on power system reliability while performing an optimal coordination among three energy sources within microgrids, namely renewable energy conversion, energy storage and micro-turbine generation. This coordination is modeled when applying sequential Monte Carlo simulations, which seek the best placement and sizing of microgrids in composite reliability of a deregulated power system that minimize the risk of cascading failure leading to blackouts subject to fixed investment budget. The performance of the approach is evaluated on the Roy Billinton Test System (RBTS) and the IEEE Reliability Test System (RTS). Simulation results show that in both power systems, microgrids contribute to the improvement of system reliability and the decrease of the risk of cascading failure. / Ph. D.

<p>The risk assessment process and the subsequent risk management measures need tobe constantly evaluated, updated and improved. This thesis contributes to that workby considering, and suggesting improvements, regarding aspects like userfriendliness,transparency, accuracy, consistency, data reporting, data selection anddata evaluation.The first paper in this thesis reports from an empirical investigation of themotivations, intentions and expectations underlying the development andimplementation of a voluntary industry owned environmental classification systemfor pharmaceuticals. The results show that the purpose of the classification systemis to provide information, no other risk reduction measures are aimed for.The second paper reports from an evaluation of the accuracy and the consistency ofthe environmental risk assessments conducted within the classification system. Theresults show that the guideline recommendations were not followed in several casesand consequently alternative risk ratios could be determined for six of the 36pharmaceutical substances selected for evaluation in this study. When additionaldata from the open scientific literature was included the risk ratio was altered formore than one-third of the risk assessments. Seven of the 36 substances wereassessed and classified by more than one risk assessor. In two of the seven cases,different producers classified the same substance into different classificationcategories.The third paper addresses the question whether non-standard ecotoxicity data couldbe used systematically in environmental risk assessments of pharmaceuticals. Fourdifferent evaluation methods were used to evaluate nine non-standard studies. Theevaluation result from the different methods varied at surprisingly high rate and theevaluation of the non-standard data concluded that the reliability of the data wasgenerally low.</p> / QC 20100929

A novel concept of multiple deterministic analyses is proposed to design safer and more damage-tolerant structures, particularly when excited by dynamic including seismic loading in time domain. Since the presence of numerous sources of uncertainty cannot be avoided or overlooked, the underlying risk is estimated to compare design alternatives. To generate the implicit performance functions explicitly, the basic response surface method is significantly improved. Then, several surrogate models are proposed. The advanced factorial design and Kriging method are used as the major building blocks. Using these basic schemes, seven alternatives are proposed. Accuracies of these schemes are verified using basic Monte Carlo simulations. After verifying all seven alternatives, the capabilities of the three most desirable schemes are compared using a case study. They correctly identified and correlated damaged states of structural elements in terms of probability of failure using only few hundreds of deterministic analyses. The modified Kriging method appears to be the best technique considering both efficiency and accuracy. Estimating the probability of failure, the post-Northridge seismic design criteria are found to be appropriate. After verifying the proposed method, a Site-Specific seismic safety assessment method for nonlinear structural systems is proposed to generate a suite of ground excitation time histories. The information of risk is used to design a structure more damage-tolerant. The proposed procedure is verified and showcased by estimating risks associated with three buildings designed by professional experts in the Los Angeles area satisfying the post-Northridge design criteria for the overall lateral deflection and inter-story drift. The accuracy of the estimated risk is again verified using the Monte Carlo simulation technique. In all cases, the probabilities of collapse are found to be less than 10% when excited by the risk-targeted maximum considered earthquake ground motion satisfying the intent of the code. The spread in the reliability indexes for each building for both limit states cannot be overlooked, indicating the significance of the frequency contents. The inter story drift is found to be more critical than the overall lateral displacement. The reliability indexes for both limit states are similar only for few cases. The author believes that the proposed methodology is an alternative to the classical random vibration and simulation approaches. The proposed site-specific seismic safety assessment procedure can be used by practicing engineers for routine applications. The proposed reliability methodology is not problem-specific. It is capable of handling systems with different levels of complexity and scalability, and it is robust enough for multi-disciplinary routine applications. In order to show the multi-disciplinary application of the proposed methodology, the probability of failure of lead-free solders in Ball Grid Array 225 surface-mount packaging for a given loading cycle is estimated. The accuracy of the proposed methodology is verified with the help of Monte Carlo simulation. After the verification, probability of failure versus loading cycles profile is calculated. Such a comprehensive study of its lifetime behavior and the corresponding reliability analyses can be useful for sensitive applications.

The risk assessment process and the subsequent risk management measures need tobe constantly evaluated, updated and improved. This thesis contributes to that workby considering, and suggesting improvements, regarding aspects like userfriendliness,transparency, accuracy, consistency, data reporting, data selection anddata evaluation.The first paper in this thesis reports from an empirical investigation of themotivations, intentions and expectations underlying the development andimplementation of a voluntary industry owned environmental classification systemfor pharmaceuticals. The results show that the purpose of the classification systemis to provide information, no other risk reduction measures are aimed for.The second paper reports from an evaluation of the accuracy and the consistency ofthe environmental risk assessments conducted within the classification system. Theresults show that the guideline recommendations were not followed in several casesand consequently alternative risk ratios could be determined for six of the 36pharmaceutical substances selected for evaluation in this study. When additionaldata from the open scientific literature was included the risk ratio was altered formore than one-third of the risk assessments. Seven of the 36 substances wereassessed and classified by more than one risk assessor. In two of the seven cases,different producers classified the same substance into different classificationcategories.The third paper addresses the question whether non-standard ecotoxicity data couldbe used systematically in environmental risk assessments of pharmaceuticals. Fourdifferent evaluation methods were used to evaluate nine non-standard studies. Theevaluation result from the different methods varied at surprisingly high rate and theevaluation of the non-standard data concluded that the reliability of the data wasgenerally low. / QC 20100929

The electrical grid balances production capacity and demand in real-time. With an increased demand for renewable energy sources, challenges such as stability of the grid, the balance between generation and demand, and power quality occur. One way to deal with the variability is by introducing Battery Energy Storage System (BESS) to the electric grid. To ensure a stable connection, the BESS must be reliable, and much research has been carried out on the BESS reliability. However, the previous studies have mainly focused on the DC reliability of the system and little research has been conducted on the AC side of a BESS. This thesis aims to provide a reliability-based maintenance strategy for the AC-side of a BESS. First, the reliability index of each AC component is calculated with established models, and based on the results, the maintenance strategy is developed. It is shown that the load current and ambient temperature are the two main parameters that affect a BESS’s reliability. For longer periods of continuous operation, the reliability declines with time and the failure rate increases. The most suitable maintenance strategy is a combination of preventive and predictive. The frequency of the scheduled preventive maintenance differs between the AC components since the schedule is based on the results from individual reliability indices. The preventive maintenance uses the condition monitoring method to observe some key elements such as DC-bus neutral current and junction temperature. / Det elektriska distributionsnätet balanserar produktionskapacitet och efterfrågan i realtid. I samband med den ökade efterfrågan av förnyelsebara energikällor uppstår nya utmaningar, såsom nätstabilitet, balans mellan produktion och efterfrågan och kvaliteten. Ett sätt att hantera variationen är att introducera Batterienergilagringssystem (BESS) till distributionsnätet. För att säkerställa en stabil anslutning måste BESS vara tillförlitlig och mycket forskning har utförts kring BESS tillförlitlighet. Fokus från de tidigare studierna har dock främst varit på DC-sidan av systemet och nästintill ingen forskning har fokuserats på den AC-sidan och dess tillförlitlighet. Denna masteruppsats syftar till att tillhandahålla en tillförlitlighetsbaserad underhållsstrategi för AC-sidan av en BESS. Först beräknas tillförlitlighetsindexet för varje AC-komponent från etablerade modeller och den underhållsstrategin utvecklas senare baserats på resultaten från tillförlighetsindex. Det visar sig att strömmen och omgivningstemperaturen är de två huvudparametrarna som påverkar tillförlitligheten. Vid längre perioder av kontinuerlig drift minskar tillförlitligheten med tiden och felfrekvensen ökar. Den mest lämpliga underhållsstrategin är en kombination av förebyggande och förutsägande. Frekvensen av det schemalagda förebyggande underhållet skiljer sig mellan AC-komponenterna eftersom schemat är baserat på resultaten från individuella tillförlitlighetsindex. Det förebyggande underhållet använder tillståndsövervakningsmetoden för att observera några nyckelelement såsom likström och kopplingstemperatur.

A complex process like risk assessment and the subsequent risk management decision makingshould be regularly evaluated, in order to assess the need to improve its workings. In this thesisthree related matters are addressed: evaluation of environmental risk management strategies,evaluation of environmental risk assessments, and how ecotoxicity data from the open scientificliterature can be used in a systematic way in regulatory risk assessments. It has resulted in thefollowing: a publically available database with ecotoxicity data for pharmaceuticals (Paper I); anevaluation and review of the Swedish Environmental Classification and Information System forpharmaceuticals (Papers II and III); a comparison of current reliability evaluation methods and areliability evaluation of ecotoxicity data (Paper IV); and an improved reliability and relevancereporting and evaluation scheme (Paper V).There are three overall conclusions from this thesis:(1) Ecotoxicity data from the open scientific literature is not used to the extent it could be inregulatory risk assessment of chemicals. Major reasons for this are that regulators prefer standarddata and that research studies in the open scientific literature can be reported in a way that affectstheir reliability and the user-friendliness. To enable the use of available data more efficiently actionsmust be taken by researchers, editors, and regulators. A more structured reliability and relevanceevaluation is needed to reach the goal of transparent, robust and predictable risk assessments.(2) A risk assessment is the result of the selected data and the selected methods used in theprocess. Therefore a transparent procedure, with clear justifications of choices made, is necessaryto enable external review. The risk assessments conducted within the Swedish EnvironmentalClassification and Information System for pharmaceuticals vary in their transparency and choice ofmethod. This could come to affect the credibility of the system since risk assessments are notalways consistent and guidelines are not always followed.(3) The Swedish Environmental Classification and Information System for pharmaceuticalscontribute, in its current form, to data availability and transparency but not to risk reduction. Thesystem has contributed to the general discussion about pharmaceuticals’ effect on the environmentand made data publicly available. However, to be an effective risk reduction tool this is not sufficient. / <p>QC 20121119</p> / MistraPharma / Formas - Evaluation of the Swedish Environmental Classification and Information System for Pharmaceutcals.