| 1. |
- Babu, Sajeesh, 1987-, et al.
(författare)
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Analyses of Smart Grid Technologies and Solutions from a System Perspective
- 2015
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Ingår i: Smart Grid Technologies - Asia (ISGT ASIA), 2015 IEEE Innovative. - : IEEE conference proceedings. - 9781509012374 ; , s. 1-5
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Konferensbidrag (refereegranskat)abstract
- 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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| 2. |
- Babu, Sajeesh, et al.
(författare)
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Analysing Correlated Events in Power System Using Fault Statistics
- 2016
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Ingår i: Probabilistic Methods Applied to Power Systems (PMAPS), 2016 International Conference on. - : IEEE. - 9781509019700
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 3. |
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| 4. |
- Babu, Sajeesh, 1987-
(författare)
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Reliability Evaluation of Distribution ArchitecturesConsidering Failure Modes and Correlated Events
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 5. |
- Babu, Sajeesh, et al.
(författare)
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Reliability Evaluation of Distribution Structures Considering the Presence of False Trips
- 2018
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Ingår i: IEEE Transactions on Smart Grid. - : IEEE. - 1949-3053 .- 1949-3061.
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 6. |
- Babu, Sajeesh, 1987-
(författare)
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Reliability Evaluation of Distribution Systems Considering Failure Modes and Network Configuration
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Power distribution networks are recognized as the constituent part of power systems with the highest concentration of failure events. Even though the faults in distribution networks have a local effect when compared to the generation and transmission sides, major contingency escalation events are being more frequently reported from this section. The various aspects regarding the reliability and performance of distribution networks are identified as an important topic. Integration of new technologies, automation and increased penetration of distributed generation is expected to make improving and even sustaining high reliability standards a complex task. This thesis presents developed approaches to quantify and analyze the complex correlated failure probabilities of different failure modes in distribution networks. A theoretical simulation model that relates to real world data to measure false tripping probabilities is developed and tested. More simplified approaches that utilities can exercise with readily available data in fault registers are also established. Optimal configurations that could improve system performance and respective investment costs are analyzed and savings in system reliability at the cost of grid investments are modelled. The optimization helps in prioritizing the most critical investments by considering the system impact of reconfigurations focusing on meeting customer demands and respecting transfer capacities of weak links. The value of existing networks and willingness of the grid owner in investing can be integrated into suggestive alterations to assist decision making in planning and maintenance allocation. The thesis makes both system specific and generalizable observations from detailed data collection from power utilities. The observations and results have potential in aiding future research by giving important understanding of the reliability impacts of network structures and of control and protection equipment.
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| 7. |
- Bergerland, Sune, et al.
(författare)
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Summary of the Swedish tariff regulation and impact of changes on investment strategies
- 2015
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Konferensbidrag (refereegranskat)abstract
- This paper evaluates how upcoming changes in the Swedish tariff regulation could affect distribution system operators (DSOs), with focus on reinvestment planning. This is done by general analyses as well as by authentic calculation examples of a real power distribution system. The paper describes the Swedish tariff regulation with expected changes, provides a summary of changes in Swedish laws and regulation affecting DSOs between 1996 and 2016, describes how a DSO at local distribution level conduct their reinvestments, illustrates economic calculation examples and finally presents analyses and conclude the results. Analysis results presented show that the outcome from the regulation is sensitive towards relatively small changes in WACC and age structure. The tariff cap allowed will however be significantly reduced for all tested scenarios. A reinvestment rate of in average~10 % regarding meters and IT and ~2.5 % regarding all other categories could be a rough guideline to meet the new incentives, but that could differ depending on the actual age structure of the DSO.
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| 8. |
- Brodersson, Anna Lilly, et al.
(författare)
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Towards health assessment : Failure analysis and recommendation of condition monitoring techniques for large disconnector populations
- 2016
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Ingår i: CIRED Workshop -. - Helsinki : Institution of Engineering and Technology. ; , s. 4-
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 9. |
- Colmenares, Juan, 1989-, et al.
(författare)
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Reliability Analysis of a High-Efficiency SiC Three-Phase Inverter
- 2016
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Ingår i: IEEE Journal of Emerging and Selected Topics in Power Electronics. - : IEEE. - 2168-6777 .- 2168-6785. ; 4:3, s. 996-1006
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Tidskriftsartikel (refereegranskat)abstract
- Silicon carbide as an emerging technology offers potential benefits compared with the currently used silicon. One of these advantages is higher efficiency. If this is targeted, reducing the on-state losses is a possibility to achieve it. Parallel-connecting devices decrease the on-state resistance and therefore reduce the losses. Furthermore, increasing the amount of components such as parallel connection of devices introduces an undesired tradeoff between efficiency and reliability, since an increased component count increases the probability of failure. A reliability analysis has been performed on a three-phase inverter rated at 312 kVA, using parallel-connected power modules. This analysis shows that the gate voltage stress has a high impact on the reliability of the complete system. Decreasing the positive gate-source voltage could, therefore, increase the reliability of the system approximately three times without affecting the efficiency significantly. Moreover, adding redundancy in the system could also increase the mean time to failure by approximately five times.
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| 10. |
- Colmenares, Juan, 1989-, et al.
(författare)
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Reliability analysis of a high-efficiency SiC three-phase inverter for motor drive applications
- 2016
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Ingår i: 2016 IEEE Applied Power Electronics Conference and Exposition (APEC). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781467395502 ; , s. 746-753
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Konferensbidrag (refereegranskat)abstract
- Silicon Carbide as an emerging technology offers potential benefits compared to the currently used Silicon. One of these advantages is higher efficiency. If this is targeted, reducing the on-state losses is a possibility to achieve it. Parallel-connecting devices decrease the on-state resistance and therefore reducing the losses. Furthermore, increasing the amount of components introduces an undesired tradeoff between efficiency and reliability. A reliability analysis has been performed on a three-phase inverter for motor drive applications rated at 312 kVA. This analysis has shown that the gate voltage stress determines the reliability of the complete system. Nevertheless, decreasing the positive gate-source voltage could increase the reliability of the system approximately 8 times without affecting the efficiency significantly. Moreover, adding redundancy in the system could also increase the mean time to failure approximately 5 times.
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