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  • 1.
    Jürgensen, Jan Henning
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Nordström, Lars
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Hilber, Patrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Estimation of Individual Failure Rates for Power System Components Based on Risk Functions2019In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 34, no 4, p. 1599-1607Article in journal (Refereed)
    Abstract [en]

    The failure rate is essential in power system reliability assessment and thus far, it has been commonly assumed as constant. This is a basic approach that delivers reasonable results. However, this approach neglects the heterogeneity in component populations, which has a negative impact on the accuracy of the failure rate. This paper proposes a method based on risk functions, which describes the risk behavior of condition measurements over time, to compute individual failure rates within populations. The method is applied to a population of 12 power transformers on transmission level. The computed individual failure rates depict the impact of maintenance and that power transformers with long operation times have a higher failure rate. Moreover, this paper presents a procedure based on the proposed approach to forecast failure rates. Finally, the individual failure rates are calculated over a specified prediction horizon and depicted with a 95% confidence interval.

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  • 2.
    Mashad Nemati, Hassan
    et al.
    Halmstad University.
    Pinheiro Sant'Anna, Anita
    Halmstad University.
    Nowaczyk, Sławomir
    Halmstad University.
    Jürgensen, Jan Henning
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Hilber, Patrik
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Reliability Evaluation of Power Cables Considering the Restoration Characteristic2019In: International Journal of Electrical Power & Energy Systems, ISSN 0142-0615, E-ISSN 1879-3517, Vol. 105, p. 622-631Article in journal (Refereed)
    Abstract [en]

    In this paper Weibull parametric proportional hazard model (PHM) is used to estimate the failure rate of every individual cable based on its age and a set of explanatory factors. The required information for the proposed method is obtained by exploiting available historical cable inventory and failure data. This data-driven method does not require any additional measurements on the cables, and allows the cables to be ranked for maintenance prioritization and repair actions.

    Furthermore, the results of reliability analysis of power cables are compared when the cables are considered as repairable or non-repairable components. The paper demonstrates that the methods which estimate the time-to-the-first failure (for non-repairable components) lead to incorrect conclusions about reliability of repairable power cables.

    The proposed method is used to evaluate the failure rate of each individual Paper Insulated Lead Cover (PILC) underground cables in a distribution grid in the south of Sweden.

  • 3.
    Jürgensen, Jan Henning
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Nordström, Lars
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Hilber, Patrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Brodersson, Anna Lilly
    Vattenfall Eldistribution AB.
    Andreasson, Elin
    Vattenfall Eldistribution AB.
    Assessment of Explanatory Variables on the Failure Rate of Circuit Breakers Using the Proportional Hazard Model2018In: 2018 POWER SYSTEMS COMPUTATION CONFERENCE (PSCC), Dublin, Ireland: IEEE conference proceedings, 2018, article id 8442567Conference paper (Refereed)
    Abstract [en]

    This paper utilises the proportional hazard model to understand and quantify the impact of explanatory variables on the failure rate of circuit breakers (CB). Particularly, 4496 work orders with 2622 high voltage CBs are investigated with an occurrence of 281 major failures. Different explanatory variables such as CB type, manufacturer, preventive maintenance (PM), and others are gathered to quantify their significance and magnitude of their effect. The results present that PM has a positive impact, the number of operations within the last year a negative impact, and age has a small but negative impact on the failure rate. The CB type is not significant in all analyses which can be explained by examining the PM and age of these CB types. This paper contributes to the understanding of how explantatory variables impact the failure rate which is essential for power system asset management.

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  • 4.
    Jürgensen, Jan Henning
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Nordström, Lars
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Hilber, Patrik
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Estimation of Individual Failure Rates for Power System Components based on Risk Functions2018Manuscript (preprint) (Other academic)
    Abstract [en]

    The failure rate is essential in power system reliability assessment and thus far it has been commonly assumed as constant. This is a basic approach that delivers reasonable results. However, this approach neglects the heterogeneity in component populations which has a negative impact on the accuracy of the failure rate. This paper proposes a method based on risk functions, which describes the risk behaviour of condition measurements over time, to compute individual failure rates within populations. The method is applied to a population of 12 power transformers on transmission level. The computed individual failure rates depict the impact of maintenance and that power transformers with long operation times have a higher failure rate. Moreover, the paper presents a procedure based on the proposed approach to forecast failure rates. Finally, the individual failure rates are calculated over a specified prediction horizon and depicted with a 95\% confidence interval.

  • 5.
    Jürgensen, Jan Henning
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Brodersson, Anna Lilly
    Vattenfall Eldistribution AB.
    Nordström, Lars
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Hilber, Patrik
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Impact Assessment of Remote Control and Preventive Maintenance on the Failure Rate of a Disconnector Population2018In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 33, no 4, p. 1501-1509Article in journal (Refereed)
    Abstract [en]

    This paper presents the impact of different explanatory variables such as remote control availability and conducted preventive maintenance, among others, on failure statistics of a disconnector population in Sweden using the proportional hazard model. To do so, 2191 work orders were analysed which included 1626 disconnectors and 278 major failures. Here, the results show that the remote control availability for disconnectors - an example of such Smart Grid technology - has a negative effect on the failure rate, whereas preventive maintenance has a positive impact. It is also shown that the disconnector age is not significant and that certain disconnector types have a significant and positive correlation towards failures when compared to other disconnector types. The results increase the understanding of disconnector failures to improve asset management.

  • 6.
    Jürgensen, Jan Henning
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Individual Failure Rate Modelling and Exploratory Failure Data Analysis for Power System Components2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A set of vital societal functions such as health and safety are necessary for today's society to function and to secure the life of its individuals. Infrastructure is required to provide and maintain these functions. This for society critical infrastructure includes electronic communication technology, transport systems, oil \& gas supply, water supply, and the supply of electric power. The electric power system plays a central role in the critical infrastructure since it is required to operate all others. Therefore, outages in the power system can have severe consequences not solely for the supply of electricity but also for the supply of water, gas, and food. To provide a reliable and safe power supply, power system operators are applying asset management strategies to investigate, plan, maintain, and utilize the system and its components while improving the performance under its own financial constraints.

    One approach to increase the reliability of the power grid while decreasing costs is maintenance planning, scheduling, and optimization. To optimize maintenance, a reliability measure for power system components is required. The failure rate, which is the probability of failure in a predefined interval, is utilized in maintenance optimization. Thus far, an average failure rate has been assigned to all components of the same type due to a shortage of component failure data. However, this limits the accuracy of maintenance techniques since the component heterogeneity is neglected. Moreover, the actual failure rate is being underrated or overrated and it is a challenge to identify the impact of conducted maintenance tasks.

    This thesis presents how the failure rate accuracy can be improved despite limited failure data available. Firstly, an introduction to failure rate modelling theory, concepts, and definitions is given to provide a common understanding for the later chapters and papers. Secondly, regression models are presented which can be used to model, predict, and characterise the failure rate and failure intensity for power system components. The Cox regression and regression models for count data are applied to two case studies of disconnector and circuit breaker failure data. The results contribute to an improved modelling of the failure rate on individual level but also improve the understanding of risk factor's impact on component failures. However, the aforementioned regression models have rarely been applied in the power system domain due to the limited failure data. Thirdly, the necessity to distinguish between population and individual failure rates is illustrated and risk factors and methods are presented, which are frequently used in failure rate modelling. Moreover, the thesis presents a method to calculate and predict individual failure rates despite the occurrence of actual failures which is of particular advantage for new components.

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  • 7.
    Jürgensen, Jan Henning
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Nordström, Lars
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Hilber, Patrik
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Brodersson, Anna Lilly
    Vattenfall Eldistribution AB.
    Andreasson, Elin
    Vattenfall Eldistribution AB.
    Goel, Lalit
    Nanyang Technological University Singapore.
    Modelling of Recurrent Circuit Breaker Failures with Regression Models for Count Data2018Conference paper (Refereed)
    Abstract [en]

    High voltage circuit breaker (CB) are of fundamental importance to protect and operate the power system. To improve their performance and to better predict failures, it is necessary to understand the effect of covariates such as preventive maintenance, age, voltage level, and the CB type. A straightforward approach is to investigate recurrent failures with regression models for count data. In this paper, several regression models are developed to estimate the impact of the aforementioned covariates to predict the recurrence of failures. The results show that age has a significant and negative impact, preventive maintenance before the first failure has a positive impact, and that the voltage level has a negative impact. Moreover, the Poisson, Negative Binomial, and zero-inflated models are compared. The comparison shows that the Negative Binomial model has the best fit to the studied recurrent failure data.

  • 8.
    Jürgensen, Jan Henning
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Scheutz Godin, Axel
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Hilber, Patrik
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Health index as condition estimator for power system equipment: A critical discussion and case study2017In: CIRED - Congrès International des Réseaux Electriques de Distribution, 2017., Institution of Engineering and Technology, 2017, Vol. 2017, p. 202-205, article id 1Conference paper (Refereed)
    Abstract [en]

    Over the past decade, the health index has become an increasingly popular asset management tool in utilities. The health index as a condition indicator can improve the decision making process. However, it also has challenges which need to be considered during development and implementation. This paper addresses the advantages and disadvantages of the health index as a condition indicator in a critical discussion. Moreover, a case study is presented where a health index is calculated for three transmission power transformers. The case study illustrates that age and the load factor included in the health index calculation lead to an immoderately high health index for the transformers T2 and T3. Thus, the paper ageing of the transformer windings are used instead which results in a plausible condition representation of all three transformers. The case study also demonstrates that the observation of condition trends over time is lost if the health index is transformed into a linguistic expression.

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  • 9.
    Sadik, Diane-Perle
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Colmenares, Juan
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems. ABB Corporate Research.
    Jürgensen, Jan-Henning
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Giezendanner, Florian
    GE, Sweden.
    Ranstad, Per
    GE Power, Sweden.
    Introduction of SiC MOSFETs in Converters based on Si IGBTs: A Reliability and Efficiency Analysis2017In: 2017 IEEE 3rd International Future Energy Electronics Conference and ECCE Asia, IFEEC - ECCE Asia 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 1680-1685, article id 7992300Conference paper (Refereed)
    Abstract [en]

    Silicon Carbide (SiC) Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) have the potential to increase the power density in power electronics converters compared to the currently used silicon (Si). Their benefits are higher efficiency, higher switching speeds, and higher operating temperatures. Moreover, SiC MOSFETs, which are normally-off, offer the possibility to directly replace Si Isolated-Gate-BipolarTransistors (IGBTs) in already existing converter designs with minimal circuit changes. Nevertheless, as an emerging technology, the reliability performance remains to be investigated. A reliability analysis has been performed based on a full-bridge resonant converter rated at 60 kW for modern Electrostatic Precipitator (ESP) power supplies. This analysis shows that introducing SiC devices will increase the lifetime of the converter while reducing the losses. The investment costs of replacing the Si IGBTs with SiC MOSFETs can thus be covered with the reduction of the losses over the economical operational lifetime. Furthermore, a theoretical analysis on how introducing SiC MOSFETs could increase the power density of the converter while maintaining the efficiency and the reliability. Finally, an analysis on introducing redundancy as a way to improve the reliability of the system has been performed.

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  • 10.
    Jürgensen, Jan Henning
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Brodersson, Anna Lilly
    Vattenfall Eldistribution AB.
    Hilber, Patrik
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Nordström, Lars
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    The Proportional Hazard Model and the Modelling of Recurrent Failure Data: Analysis of a Disconnector Population in Sweden2017In: 2017 Cigré SC B3 (Substations) Colloquium, 18 - 20 September 2017, Recife, Brazil, 2017, p. 1-8Conference paper (Refereed)
    Abstract [en]

    Failure rate estimation is an important tool for planning and operating decision making in asset management of the power system. Moreover, the knowledge of how different explanatory variables impact the failure rate of the power system equipment is crucial for substation design. This study investigates 2191 work orders of 1626 non-current breaking disconnectors with 344 major failures. In particular, this paper analyses the disconnector failure data regarding recurrent failure data. Since the original PHM cannot handle recurrent event data, different extensions were developed such as the Andersen-Gill (AG), Prentice, Williams and Peterson (PWP), and the Wei, Lin, and Weissfeld (WLW) model. These models are applied to the disconnector dataset with 140 recurrent time-to-failure processes. The explanatory variables age at admission, remote control, preventive maintenance, and voltage level are assessed. The results show that preventive maintenance has a significant and positive impact on the recurrences with all tested methods. Also remote control, voltage level, and age are significant covariates. Compared to the single failure study previously conducted, where age had no significance, age is significant when assessing the recurrent failure which is the most critical difference to the analysis without recurrences.

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  • 11.
    Jürgensen, Jan Henning
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Nordström, Lars
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Hilber, Patrik
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A Review and Discussion of Failure Rate Heterogeneity in Power System Reliability Assessment2016Manuscript (preprint) (Other academic)
    Abstract [en]

    The failure rate is a reliability measure which isused for planning and operation of the power system. Thus far, average or experience based failure rates were applied to power system equipment due to their straightforward implementation. However, this approach limits the accuracy of the gained resultsand neglects the important differentiation between populationand individual failure rates. Hence, this paper discusses and demonstrates the necessity to distinguish between populationand individual failure rates and reviews the existing literature offailure rate estimation within the power system domain. The literature is categorized into statistical data driven approaches and failure rate modelling with focus on different criteria whichcan be used to describe the heterogeneity within populations. The review reveals that the environmental impact was modelled predominantly.

  • 12.
    Jürgensen, Jan Henning
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Nordström, Lars
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Hilber, Patrik
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A Review and Discussion of Failure Rate Heterogeneity in Power System Reliability Assessment2016Conference paper (Refereed)
    Abstract [en]

    The failure rate is a reliability measure which isused for planning and operation of the power system. Thus far, average or experience based failure rates were applied to power system equipment due to their straightforward implementation. However, this approach limits the accuracy of the gained resultsand neglects the important differentiation between populationand individual failure rates. Hence, this paper discusses and demonstrates the necessity to distinguish between populationand individual failure rates and reviews the existing literature offailure rate estimation within the power system domain. The literature is categorized into statistical data driven approaches and failure rate modelling with focus on different criteria whichcan be used to describe the heterogeneity within populations. The review reveals that the environmental impact was modelled predominantly.

  • 13.
    Jürgensen, Jan Henning
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Condition-based Failure Rate Modelling for Individual Components in the Power System2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The electrical power grid is one of the most important infrastructures in the modernsociety. It supplies industrial and private customers with electricity and supportsother critical infrastructures such as the water supply. Thus, it is significant that the power grid is a reliable system. However, the power system experiences a hugetransition from classical production methods such as coal and nuclear power plantsto distributed renewable energy forms such as wind energy and photovoltaic. This change to a more distributed system challenges the existing power grid as well as the traditional business models of electric utilities. Thus, cost minimization to increase profitability and improvement of the power grid to increase customer satisfactionare in the focus. One approach to increase the reliability of the grid and decrease maintenance costs is a condition-based maintenance approach which requirescondition monitoring techniques.

    This thesis introduces into failure rate modelling for individual power system components and develops a method to calculate individual failure rates based onthe average failure rate, failure statistics, and condition monitoring data. This approach includes the analysis of failure statistics to identify failure causes and failure locations which are population characteristics but can be utilized to describe the heterogeneity within the population. Thus, the thesis first introduces into the topic of failure analysis and heterogeneity in populations. Different factors are identified and categorized which describe the condition development of a component overtime. Then, the literature within failure rate estimation is reviewed to present the factors which are used within failure rate modelling and to outline the existingmethods which consider the individual. However, limitations are discussed which emphasize the demand for a new approach. Consequently, this thesis introduce intoa new approach for estimating the failure rate for individual components.

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  • 14.
    Wallnerström, Carl Johan
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Bertling Tjernberg, Lina
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Hilber, Patrik
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Jürgensen, Jan Henning
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Framework for System Analyses of Smart Grid Solutions with Examples from the Gotland Case2016In: 2016 International Conference on Probabilistic Methods Applied to Power Systems (PMAPS), IEEE, 2016Conference paper (Refereed)
    Abstract [en]

    This paper presents results from a study on the impact of smart grid solutions, which includes development of a generic framework for power system analyses. The study has been performed as one of several independent studies, part of a national governmental task on smart grid in Sweden. A large amount of weather data, along with electricity consumption and wind power generation data, have been analyzed. Achieved results from these initial analyses can be used as reference material and have also been used within case studies presented. The proposed framework is flexible and numerous combinations of scenarios are possible to define. Integration of wind and solar power, analyses of transfer limits using static or dynamic rating and energy storage can be considered as well as weather effects. Results show how power systems can handle more electricity consumption and generation. The study shows that Smart Grid solutions are beneficial for resource efficient electricity grids. Moreover, different risk levels with respect to increased load can be included. Case study results show that energy storages most of the time will be unused, but that they can be used to increase the system reliability.

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  • 15.
    Jürgensen, Jan Henning
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Nordström, Lars
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Hilber, Patrik
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Individual failure rates for transformers within a population based on diagnostic measures2016In: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 141, p. 354-362Article in journal (Refereed)
    Abstract [en]

    The high monetary value of a transformer has placed the transformer life-time optimization into the focus of asset management. The average failure rate has created reasonable results within reliability modeling, however, it cannot reflect the probability of failure for an individual transformer. In this paper, a method is introduced to calculate individual failure rates for a transformer population based on failure statistics and diagnostic measurements such as dissolved gas, and 2-furfuraldehyde analysis. The method is applicable to all types of components and the comprehensibility makes it effective for practical implementation. The results are evaluated against two health indices based on a weight factor and fuzzy logic. It can be observed that the presented individual failure rates are plausible representatives of the transformer's probability of failure. Therefore, the results can also be utilized for asset management decision-making.

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  • 16. Brodersson, Anna Lilly
    et al.
    Hilber, Patrik
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Jürgensen, Jan Henning
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Towards health assessment: Failure analysis and recommendation of condition monitoring techniques for large disconnector populations2016In: CIRED Workshop -, Helsinki, 2016, p. 4-Conference paper (Refereed)
    Abstract [en]

    Condition monitoring of power system equipment is an important part of asset management. Hence, health indices were developed to describe the equipment condition in a linguistic form with the obtained data. The development of health indices requires knowledge about the equipment population under investigation to consider all important factors. Therefore, this paper investigates the failure data of a large disconnector population to identify population characteristics such as failure modes and failure locations. The analysis showed that the functions maneuverability and current carrying are essential to monitor. Moreover, this paper discusses condition monitoring techniques for disconnector and their applicability in large populations. The paper concludes that even without cost intensive investments in condition measurements or higher preventive maintenance costs, a condition evaluation can be performed.

  • 17.
    Jürgensen, Jan Henning
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Nordström, Lars
    KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
    Hilber, Patrik
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A Scorecard Approach to Track Reliability Performance of Distribution System Operators2015In: CIRED 2015: 23rd International Conference on Electricity Distribution, CIRED - Congrès International des Réseaux Electriques de Distribution, 2015Conference paper (Refereed)
    Abstract [en]

    Firstly, this paper reviews the current process of reporting reliability data in Sweden. Limitations of reliability indices such as SAIDI and SAIFI are discussed and the need for more reliability measures is stated. The paper suggests the introduction of a reliability performance scorecard to analyse reliability measures in an organized system under different aspects. Furthermore, a set of measurements is provided that can be used to assess a utility’s reliability performance. The use of the scorecard is discussed and its applicability for implementing and tracking regulations. This would result in a better policy-making and a decreased pressure on electric utilities due to a higher understanding of what companies invest to achieve a reliable supply of energy.

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  • 18.
    Babu, Sajeesh
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Jürgensen, Jan Henning
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Wallnerström, Carl Johan
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Hilber, Patrik
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Tjernberg, Lina Bertling
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Analyses of Smart Grid Technologies and Solutions from a System Perspective2015In: Smart Grid Technologies - Asia (ISGT ASIA), 2015 IEEE Innovative, IEEE conference proceedings, 2015, p. 1-5, article id 7387089Conference paper (Refereed)
    Abstract [en]

    This paper consolidates the data, analysis andobservations from a case study conducted in cooperation withthe Smart Grid Gotland project. The analysis identifies howelectrical power consumption interacts with distributedelectricity generation such as wind and solar power andpresents how it correlates to weather data and smart gridsolutions. The analysis model developed based on the Gotlandnetwork is generic and hence can be functional in investigatingother power networks of different size, voltage level andstructures. The key observations from the study of smart gridsolutions such as dynamic load capacity and energy storagesolutions are specified. Based on the project, an overview offuture risks and opportunities of smart grid systems is presented.

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    Analyses of Smart Grid Technologies and Solutions from a System Perspective
  • 19.
    Wallnerström, Carl Johan
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Bertling Tjernberg, Lina
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Hilber, Patrik
    KTH, School of Electrical Engineering (EES).
    Babu, Sajeesh
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Jürgensen, Jan Henning
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Analys av smartaelnätsteknologier inom kategorin elnätslösningar2014Report (Other academic)
    Abstract [sv]

    Denna rapport presenterar resultat från en studie där inverkan av så kallade smartaelnäts­teknologier/lösningar har analyserats. Utöver egna analysresultat identifieras behov av framtida forskning, detta kompletteras med hänvisningar till fördjupningsmaterial Smarta­elnätsteknologier innebär nya möjligheter, men också nya utmaningar och risker. Ett behov av att utveckla nya metoder för tillförlitlighetsberäkningar och riskanalys har identifieras. På grund av bristande erfarenhet gällande många nya tekniker och lösningar av smartaelnäts­teknologier är det värdefullt med demonstrationsanläggningar såsom Smart Grid Gotland, varifrån indata har erhållits. Information om Smart Grid Gotland och Gotlands elkraftsystem sammanfattas i rapporten. Gotlands regionnät har även implementerats i datorverktyget NEPLAN. En visuell modell av ett elnät med integrerade smartaelnätsteknologier som kan illustrera möjligheter och utmaningar ur ett systemperspektiv. I rapporten behandlas även frågan om framtida kompetensbehov till följd av smarta elnät ur ett riskperspektiv.

     

    En stor mängd timvis väderdata har bearbetats och analyserats tillsammans med timvis data för elkonsumtion och lokal elproduktion. Samband mellan olika parametrar har identifierats, vilka kan vara värdefulla att använda sig av vid utvecklandet av smarta lösningar i elnätet. Resultat från denna initiala analys av indata har använts i genomförda analyser, men kan även vara användbarts referensmaterial i andra studier. Ett analysverktyg har tagits fram för att analysera integrering av elproduktion från både vindkraftturbiner och solkraft, analys av acceptgränser, dynamisk belastningsförmåga och energilager. Hänsyn tas till vädrets påverkan på elproduktions- och elkonsumtionsmönster samt överföringskapacitet.

     

    Dynamisk belastningsförmåga innebär att systemets överföringskapacitet varierar dynamiskt med avseende på externa parametrar såsom väder, vilket ökar möjligheten att nyttja ekraft­system mer effektivt. Analysresultat från flera olika scenarion presenteras i rapporten, vilka visar på olika exempel avseende hur elnätet kan hantera högre maxnivå av elkonsumtion och/eller elproduktion utan fysiska nätförstärkningar. I rapporten presenteras även exempel på hur denna lösning i vissa fall kan öka leveranssäkerhet. Potential av att använda sammanlagring mellan elkonsumtion och lokal elproduktion har analyserats, det vill säga hur dessa tar ut varandra. Även resultat för olika risknivåer med avseende på överlast har analyserats för flera olika scenarier, med och utan dynamisk belastningsförmåga. Om över­last endast medför ökat slitage går det att tänka sig att det kan tillåtas under korta perioder.

     

    Energilagring har analyserats ur ett teknikneutralt perspektiv och resultat redovisas som kravlistor. Av elproduktion från vindkraftturbiner respektive solkraft och elkonsumtion kan ett lika stort energilager höja maxeffekten av solkraft mer jämfört med övriga analyserade kategorier. Även energilager i systemdel innehållendes både elkonsumtion och elproduktion, vilken har problem med både import- och exportbegränsningar, har analyserats. Denna kombination balanserar ofta varandra så att överlast undviks; energilagret tar hand om de två ytterligheterna: export- respektive importtoppar. Hur energilager potentiellt kan användas för att höja leveranskvalitet har också analyserats. Energilager som hanterar överföringstoppar behöver endast användas under en liten period av årets timmar och skulle därför kunna användas för flera olika saker såsom att öka leverenssäkerhet.

     

    I ett appendix till rapporten görs en ansats till att koppla studiens innehåll till rekommendationer presenterade i Samordningsrådet för smarta elnäts handlingsplan.

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  • 20.
    Babu, Sajeesh
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Hilber, Patrik
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Jürgensen, Jan Henning
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    On the status of reliability studies involving primary and secondary equipment applied to power system2014In: 2014 International Conference on Probabilistic Methods Applied to Power Systems, PMAPS 2014 - Conference Proceedings, IEEE , 2014, p. 6960653-Conference paper (Refereed)
    Abstract [en]

    Growth in infrastructure and energy utilization consistently put forward the demand for added quality and quantity of electric power. Reliability concerns over power systems are widespread within its different associated divisions like 'primary' power system structure, protection system, control equipment, ICT (Information and Communication Technologies) etc. This paper is a review of the present status of practices regarding reliability analysis in these divisions and works towards collectively assessing some of the studies in the respective areas. The idea of integrating reliability analysis from the above areas is introduced along with pointing out the major challenges associated. A set of tools for operators to make use in these reliability evaluations and modelling are mentioned. The earlier attempts towards combined overall system reliability analysis are discussed and the approach in this regard with the help of 'control functions' is emphasised. The paper includes works dealing with theory, different methodologies and data associated with power system reliability.

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    On the Status of Reliability Studies Involving Primary and Secondary Equipment Applied to Power System
  • 21.
    Ekstedt, Niklas
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Wallnerström, Carl Johan
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Babu, Sajeesh
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Hilber, Patrik
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Westerlund, Per
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Jürgensen, Jan Henning
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Lindquist, Tommie
    Svenska kraftnät.
    Reliability Data: A Review of Importance, Use, and Availability2014Conference paper (Refereed)
    Abstract [en]

    For reliability studies of power distribution systems availability and collection of data on reliability is a key aspect. The acquirement of data can be challenging, because it endures effort and experience to know where to obtain accessible types of data. This paper gives the reader a guide to why input data to reliability analyses and asset management are useful, which data that can be obtained, and how to access the different types of data. Also, how to measure data accurately and the quality needed are discussed in the paper.

    After a general discussion on the benefits of data, we discuss the importance of knowing exactly what the data are measurements of. Furthermore, we argue that data from different contexts, even if seemingly similar, should be used with care. We also state and explain that the amount data restrict the type of analysis that can be conducted. The paper continues with a description of some examples of (to different degrees) open accessible data. Nationally collected reliability data from Swedish utilities, reported to authorities and interest organizations, are described and discussed. We discuss how Swedish weather data, which recently have become free and open, enable more studies on the weather related reliability effects, and some existing test systems are mentioned. A section follows that describes how failure and condition data are typically stored and utilized internally in organizations. Finally, we conclude that the paper is a potential guide and inspiration for anyone planning to conduct a reliability study in the future.

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    fulltext
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