This paper presents a method for modelling the different modes of failures in a substation and feeder architecture along with updating the possible false tripping scenarios in it. A traditional approach to collectively assess the failure modes using reliability block diagram is reviewed, and the method is updated to count in the unaccounted false tripping scenarios. A generalizable radial feeder branching structure is adopted and the effect of total feeder length and number of feeders from each busbar is examined and modelled with the help of the updated reliability block diagram. The modelled trends are also studied from real-world substation architectures. Thus, the analysis attains an improved estimation of the complex hidden failure probabilities combining theoretical and practical models.

Power system automation requires logical presumptions made on practical grids to correctly comprehend and manage complex and correlated faults occurring in real world systems. Traditional grid fault analysis methods lack in-depth understanding of these complex events and demand development of approaches that make use of available data to address this problem. Here, the traditional classification approach and challenges relating control equipment in power system are reviewed and a method observing the affected customers during faults along with grid design is discussed based on Swedish case study data. Various contrasting observations are made on the data recorded over two time periods to understand the trend developing over years. Moreover, it will be shown that the classification method also has potential in identifying weak spots in the grid when it comes to the reliability of control equipment.

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.

This paper proposes a method to make future failure predictions from input data on population age distribution and failure rates, using a Monte Carlo approach. In contrast to many methods used today, the method in this paper is designed to address multiple properties and assumptions simultaneously, which makes the task complicated. For example, the component population is allowed to be divided into both age and different types. The time-dependent failure rates are defined separately for each individual type, can consist of a combination of multiple different failure rates for separate modes, and can be of practically any shape. Furthermore, a volatility measure for the failure rates is introduced and used to model the uncertainties in failure rate estimates. The method handles investment and reinvestment scenarios as well as different restoration models, such as replacing a failed component with a new component of a different type. As a part of the project, a stand-alone software tool was developed and presented in the paper. In the included case study, the method and the tool are shown to be useful when investigating reinvestment strategies to renew the population and decrease the expected number of future failures. The paper gives the reader useful information and understanding on how the problem of predicting the reliability of the future power system can be addressed and solved.

Power systems are in a phase of automation where intelligent components and sub-systems are employed to monitor, control and manage the grid. Quantifying the complex consequences on system reliability, from the integration of such automated and semi-automated equipment into the existing grid is important for maintenance optimisation and fault mitigation. This thesis identifies the  advanced approaches in power system reliability analysis with the potential to capture the complications and correlations in modern power grid after reviewing the traditional reliability evaluation methods.

A method for modelling the different modes of failures, possible in a substation and feeder architecture along with the probable false tripping scenarios was developed. An improved Reliability Block Diagram based approach was designed to count in the traditionally unaccounted failure cases affecting both the primary grid and the protectionand control equipment. The effect and corresponding trend of additional feeder lines in a radial distribution system on the net interruption rate experienced at load ends of feeders are derived and modelled. Such real-world substation architectures are analysed and the aforementioned trends are compared with those from the practical grid. Thus, the analysis was able to identify and measure the complex hidden failure probabilities due to both unwanted operation of breakers and functional failure of protection systems.

The measured probabilities were used to calculate the impact of protection and control equipment on system  reliability. The obtained results were verified by comparing it with the observations by energy researchers on ten years of protection system failure statistics. The application of the model and results, in optimal maintenance planning and power network optimisation are identified as the next step.

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.

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.

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.

This paper provides an overview of risk and reliability assessment techniques, some which are available for distribution system operators, and others that are in the process of development. The main contribution of this paper is showing the possibilities and benefits of detailed risk and reliability analysis. Six samples of findings from research developed over the last decade within the RCAM group (Reliability Centred Asset Management) at the Royal Institute of Technology, Stockholm Sweden, are presented. The research is directly associated with risk and asset management applied to power systems. The first three examples are within developed research, followed by three areas where great potential is seen: 1) The value of accurate thermal models of transformers; 2) The impact of tariff regulation on asset management decisions; 3) Detailed interruption studies; 4) Dynamic rating; 5) Combined risk and reliability analysis of primary equipment and control equipment; 6) Systematic diagnostic measures for asset management.