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  • 1. Arafat, Y.
    et al.
    Bertling Tjernberg, Lina
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Gustafsson, P. -A
    Experience from real tests on multiple smart meter switching2015Ingår i: IEEE PES Innovative Smart Grid Technologies Conference Europe, 2015, nr JanuaryKonferensbidrag (Refereegranskat)
    Abstract [en]

    Smart Meters (SMs) offer remote switching functionalities to the Distribution System Operators (DSOs). The DSO can switch the breaker of the SM of any customer remotely whenever needed. The DSOs are currently applying this technique for customers typically one by one when customers are changing their addresses or when contracts are terminated. The breaker functionalities of the SMs could be used for multiple customers, thereby opening up new possibilities to balance electricity consumption and production. How the technology has been functioning in practice has, however, not been fully investigated with regard to multiple SM switching. In this paper, the experience from real tests on simultaneous multiple SM switching is presented. The tests have been conducted to observe the effect of SM switching on power quality (PQ). Power Quality Meters (PQMs) had been used both at the substation as well as the customer level to measure the PQ during SM switching. This paper presents the results by showing current measurements during switching ON and OFF of multiple SMs belonging to each substation.

  • 2. Arafat, Y.
    et al.
    Bertling Tjernberg, Lina
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Gustafsson, P. -A
    Field test on multiple Smart Meter switching to study the effect on power quality at customers level2015Ingår i: 2015 IEEE Eindhoven PowerTech, PowerTech 2015, IEEE conference proceedings, 2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    Smart Meters (SMs) are undergoing an increasing deployment all over the world and have been introduced to several regions. The SMs generally have remotely accessible breakers which offer remote switching functionalities to the Distribution System Operators (DSOs). The DSOs have the possibility of using this unique functionality of SMs for various future applications, e.g., switching some loads during peak loads crisis or outage management during natural disasters. Under these conditions, the DSO can disconnect selected customers by using SM switching while continuing power supply to risk customers and emergency service providers. During multiple SM switching, the power quality (PQ) of the connected loads might be affected. This paper presents results on the impact of multiple SM switching at customer level. Data are used from a field test on multiple SM switching from a DSO in Sweden. The number of customers in this test was higher compared to the previous two tests of the work. Moreover, all customers in the selected test area were not switched in this test. Almost half of the customers in the test area were disconnected remotely using SMs while the other half of the customers remained connected with power supply to investigate the impact of SMs switching in a different way. This work observed some transient events during the SMs switching. Voltage quality was stable during the test except some flickering effects beyond the limit.

  • 3. Arafat, Yasir
    et al.
    Bertling Tjernberg, Lina
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Gustafsson, Per-Anders
    On Possibilities of Using Smart Meters for Emergency Grid Management: Analysing the Effect on Power Quality2015Ingår i: 2015 IEEE INNOVATIVE SMART GRID TECHNOLOGIES - ASIA (ISGT ASIA), 2015, artikel-id 7387158Konferensbidrag (Refereegranskat)
    Abstract [en]

    Electricity grids worldwide are continuing to be severely constrained and stretched to capacity. Certain grid conditions e.g., peak load crisis or loss of generation may lead to severe under frequency situations. Load shedding can then be useful to prevent the national grid from being overwhelmed. Typically, load shedding is done from medium voltage substation level and all customers including emergency service providers under that substation lose power. However, it is beneficial for a society to exclude emergency service providers from load shedding. Smart Meters (SMs) are generally equipped with remotely accessible switch which gives a unique opportunity to exclude prioritized customers during emergency load shedding. Distribution System Operators (DSOs) are currently using remote SM switching typically for one customer at a time. However, the SM switching technique has not been fully investigated with regard to multiple customers. In order to fulfill the gap, this paper presents results obtained from field tests on simultaneous multiple SMs switching with a main focus on the impact of multiple SMs switching on Power Quality (PQ). The results show that impact on PQ might be negligible for small number of SMs switching. Moreover, faster SMs switching and reliable communication system is found as an important prerequisite to use SMs for emergency load shedding.

  • 4.
    Babu, Sajeesh
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Jürgensen, Jan Henning
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Wallnerström, Carl Johan
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Hilber, Patrik
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Tjernberg, Lina Bertling
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Analyses of Smart Grid Technologies and Solutions from a System Perspective2015Ingår i: Smart Grid Technologies - Asia (ISGT ASIA), 2015 IEEE Innovative, IEEE conference proceedings, 2015, s. 1-5, artikel-id 7387089Konferensbidrag (Refereegranskat)
    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.

  • 5. Bahramirad, Shay
    et al.
    Khodaei, Amin
    Matevson, Julia
    Li, Zuyi
    Bertling, Lina
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Passo, Essa Aleksi
    Fotuhi-Firuzabad, Mahmud
    Special Section on Asset Management in Smart Grid2015Ingår i: IEEE Transactions on Smart Grid, ISSN 1949-3053, E-ISSN 1949-3061, Vol. 6, nr 2, s. 953-954Artikel i tidskrift (Övrigt vetenskapligt)
  • 6. Balram, Pavam
    et al.
    Tuan, Le Anh
    Bertling Tjernberg, Lina
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Centralized charging control of plug-in electric vehicles and effects on day-ahead electricity market price2015Ingår i: Plug In Electric Vehicles in Smart Grids, Springer, 2015, s. 267-299Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Global policy targets to reduce greenhouse gas emissions have led to increased interest in plug-in electric vehicles (PEV) and their integration into the electricity network. Existing electricity markets, however, are not well suited to encourage direct participation of flexible demand from small consumers such as PEV owners. The introduction of an aggregator agent with the functions of gathering, aggregating, controlling and representing the energy needs of PEV owners in the electricity market could prove useful in this regard. In this chapter, a mathematical model of PEV aggregator for participation in the day-ahead electricity market is described. The modeling is done by treating each of the individual vehicle batteries as a single large battery. The centralized charging and discharging of this battery is then scheduled based on the traveling needs of the PEV owners determined by an aggregated driving profile and the cumulative electrical energy needs of vehicles over the optimization horizon. Two methods for scheduling PEV demand named as joint scheduling method (JSM) and aggregator scheduling method (ASM) are presented. The two methods are subsequently used to observe the effects of introducing flexible scheduling of PEVs on the day-ahead market price in an IEEE test system and a Nordic test system. Results from the IEEE test system case studies will indicate that the scheduling of PEV energy through direct centralized control at high PEV penetration levels of 50 % or greater could lead to potential lowering of day-ahead market prices as compared to an indirect control method such as the use of fixed period charging. Results from the Nordic test system case study shows that controlled scheduling of PEV demand could lead to only a small increase in day-ahead market price of electricity.

  • 7. Bangalore, P.
    et al.
    Letzgus, S.
    Patriksson, M.
    Bertling, Lina
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknisk teori och konstruktion.
    Analysis of SCADA data for early fault detection with application to the maintenance management of wind turbines2016Ingår i: CIGRE Session 46, CIGRE , 2016, s. 1-10Konferensbidrag (Refereegranskat)
    Abstract [en]

    During the past decade wind turbines have proven to be a promising source of renewable power. Wind turbines are generally placed in remote locations and are subject to harsh environmental conditions throughout their lifetimes. Consequently, the failures in wind turbines are expensive to repair and cause loss of revenue due to long down times. Asset management in wind turbines can aid in assessing and improving the reliability and availability of wind turbines, thereby making them more competitive. Maintenance policies play an important role in asset management and different maintenance models have been developed for wind turbine applications. Typically, mathematical models for maintenance optimization provide either an age based or a condition based preventive maintenance schedule. Age based preventive maintenance schedules provide the owner with the possibility to financially plan for maintenance activities for the entire lifetime of the wind turbine by providing the expected number of replacements for each component. However, age based preventive maintenance schedule may not consume the operating life of the wind turbine components to the maximum. Condition based maintenance scheduling has the advantage of better utilizing the operating life of the components. This paper proposes a wind turbine maintenance management framework which utilizes operation and maintenance data from different sources to combine the benefits of age based and condition based maintenance scheduling. This paper also presents an artificial neural network (ANN) based condition monitoring method which utilizes data from supervisory control and data acquisition (SCADA) system to detect failures in wind turbine components and systems. The procedures to construct ANN models for condition monitoring application are outlined. In order to demonstrate the effectiveness of the ANN based condition monitoring method it is applied to case studies from real wind turbines. Furthermore, a mathematical model called preventive maintenance schedule with interval costs (PMSPIC) is discussed and its application to a case study within the maintenance management framework is presented. The case study demonstrates the advantage of combining both the age based and condition based maintenance scheduling methods. 

  • 8.
    Bangalore, Pramod
    et al.
    Chalmers.
    Bertling Tjernberg, Lina
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Condition Monitoring and Asset Management in the Smart Grid2016Ingår i: Condition Monitoring and Asset Management in the Smart Grid, John Wiley & Sons, 2016, s. 1-13Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    One of the main characteristics of a smart grid is the availability of large volumes of data, for example, gained from sensors. This data can be utilized as a tool to estimate the state of the system as a whole or any component within the system. In order to achieve actionable information from the variety of data that is available from smart grids, it is important to use the correct mathematical and signal processing tools. Furthermore, the future smart grid is expected to have high levels of reliability. This can be achieved by integrating the condition monitoring systems with maintenance management, wherein the focus is shifted from corrective maintenance to predictive condition-based maintenance.

    This chapter introduces the concept of reliability-centered asset management (RCAM). The RCAM approach provides the possibility of both qualitative and quantitative analysis toward optimal maintenance strategy. Furthermore, various issues with condition monitoring in smart grids have been discussed along with some literature that suggest possible solutions for these issues. Finally, a detailed case study of a data-based condition monitoring method based on artificial neural network is presented to demonstrate one of the many possibilities to use data from various measurement systems to reach actionable decisions.

  • 9.
    Bangalore, Pramod
    et al.
    Chalmers.
    Bertling Tjernberg, Lina
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Self Evolving Neural Network Based Algorithm for Fault Prognosis in Wind Turbines: A Case Study2014Ingår i: International Conference on Probabilistic Methods Applied to Power Systems (PMAPS), 2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    Asset management of wind turbines has gained increased importance in recent years. High maintenance cost and longer downtimes of wind turbines have led to research in methods to optimize maintenance activities. Condition monitoring systems have proven to be a useful tool towards aiding maintenance management of wind turbines. Methods using Supervisory Control and Data Acquisition (SCADA) system along with artificial intelligence (AI) methods have been developed to monitor the condition of wind turbine components. Various researchers have presented different artificial neural network (ANN) based models for condition monitoring of components in a wind turbine. This paper presents an application of the approach to decide and update the training data set needed to create an accurate ANN model. A case study with SCADA data from a real wind turbine has been presented. The results show that due to a major maintenance activity, like replacement of component, the ANN model has to be re-trained. The results show that application of the proposed approach makes it possible to update and re-train the ANN model. 

  • 10. Bangalore, Pramod
    et al.
    Tjernberg, Lina Bertling
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    An Artificial Neural Network Approach for Early Fault Detection of Gearbox Bearings2015Ingår i: IEEE Transactions on Smart Grid, ISSN 1949-3053, E-ISSN 1949-3061, Vol. 6, nr 2, s. 980-987Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Gearbox has proven to be a major contributor toward downtime in wind turbines. The majority of failures in the gearbox originate from the gearbox bearings. An early indication of possible wear and tear in the gearbox bearings may be used for effective predictive maintenance, thereby reducing the overall cost of maintenance. This paper introduces a self-evolving maintenance scheduler framework for maintenance management of wind turbines. Furthermore, an artificial neural network (ANN)-based condition monitoring approach using data from supervisory control and data acquisition system is proposed. The ANN-based condition monitoring approach is applied to gearbox bearings with real data from onshore wind turbines, rated 2 MW, and located in the south of Sweden. The results demonstrate that the proposed ANN-based condition monitoring approach is capable of indicating severe damage in the components being monitored in advance.

  • 11.
    Bertling, Lina
    KTH, Tidigare Institutioner, Elektrotekniska system.
    Impact of maintenance on cable failure rates2004Ingår i: 2004 IEEE POWER ENGINEERING SOCIETY GENERAL MEETING, VOLS 1 AND 2, NEW YORK: IEEE , 2004, s. 704-704Konferensbidrag (Refereegranskat)
    Abstract [en]

    This panel presentation discusses the development of a functional relationship between failure rates and maintenance measures for insulated cables. The approach has been applied to rural and urban distribution systems, and demonstrates the value of using a systematic quantitative approach for investigating the effect of different maintenance strategies.

  • 12.
    Bertling, Lina
    KTH, Tidigare Institutioner                               , Elkraftteknik.
    On reliability assessment of distribution systems and reliability centred maintenance1999Licentiatavhandling, monografi (Övrigt vetenskapligt)
  • 13.
    Bertling, Lina
    et al.
    Chalmers.
    Hilber, Patrik
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Jensen, Jolanta
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Setreus, Johan
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Wallnerström, Carl Johan
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    RADPOW development and documentation2008Rapport (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    This report summarizes the status of the computer program RADPOW. RADPOW is a program for Reliability Assessment of electrical Distribution POWer systems. It was developed at KTH School of Electrical Engineering, within the research program EKC and the research project on reliability of new electrical distribution systems. Further on, RADPOW has been used and further developed within the RCAM research group at KTH School of Electrical Engineering.

    This status report contains a brief description of the RADPOW_2006 version, the Loadflow module from the RADPOW_1999_PH version and a description of the work done in the resulting RADPOW_2007 version. This version now includes a tested load flow module and the ability to calculate the latest component importance indices developed within the RCAM research group. The source code for the program has also been restructured and commented in a more detailed level than before.

  • 14.
    Bertling, Lina
    et al.
    Chalmers.
    Larsson, Mats B-O
    Wallnerström, Carl Johan
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Evaluation of the Customer Value of Component Redundancy in Electrical Distribution Systems2005Ingår i: Power Tech, 2005 IEEE Russia, IEEE , 2005, s. 1-8Konferensbidrag (Refereegranskat)
    Abstract [en]

    A new regulatory model for the Swedish electrical distribution system operators has been proposed, and is now being implemented. The model is referred to as the Network Performance Assessment Model (NPAM). The NPAM is based on fictive reference networks. These emanate from a radial network that is reinforced with redundant components if it increases the customer value more than required investment cost for higher system reliability. The NPAM involves a paradigm shift for the Swedish DSO from a system based on compensation for costs to one based on performance. Evidently, it is of great importance to both the regulator and the different DSOs to evaluate how well the NPAM calculates the performance i.e. the customer values. The aim for this paper is to take a first step in this process; by putting light on how these redundant reference networks are created and used for the NPAM. In order to do this a comparative study has been made for a small test system where two different approaches are used for identifying the resulting redundant reference network for a system. The NPAM approach uses a Monte Carlo simulation technique, and the comparative approach uses an analytical based reliability assessment tool RADPOW, developed at KTH.

  • 15.
    Bertling, Lina
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Larsson, Mats B-O
    MML Åhus.
    Wallnerström, Carl Johan
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Review of the Swedish Network Performance Assessment Model2008Rapport (Övrigt vetenskapligt)
    Abstract [en]

    The Swedish energy agency (STEM), has developed a new regulatory model to supervise the revenues of the Distribution System Operators (DSO), referred to as the Network Performance Assessment Model (NPAM). The fundamental idea of the NPAM is that the electrical distribution system provides customer values, and the DSO is allowed to collect revenue corresponding to these values. The NPAM calculates customer values for a fictive electrical distribution system, with a total cost referred to as the Network Performance Assessment (NPA). The allowed debiting rate for a DSO is defined by the quotient of the revenue and the NPA. If the debiting rate is higher than a certain value, defined by the Energy Market Inspection (EMI) at STEM, the DSO is placed under review and could be forced to pay back revenue to customers. A lawsuit is currently in progress on this use of the NPAM, which has highlighted drawbacks in the model. This paper provides a comprehensive presentation of the NPAM. It describes in detail the different input data for the model, the steps in the calculations and the resulting cost factors. The paper also presents for the first time details on the theory underlying the calculations.

  • 16.
    Bertling, Lina M.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    On evaluation of RCM for maintenance management of electric power systems2005Ingår i: 2005 IEEE POWER ENGINEERING SOCIETY GENERAL MEETING, 2005, s. 2638-2640Konferensbidrag (Refereegranskat)
    Abstract [en]

    This panel presentation aims to propose a possible solution for how to evaluate the effect of RCM as a tool for maintenance management. The starting point is a general understanding of the RCM methodology. Further on, a quantitative approach for relating the impact of component maintenance on system reliability and total cost is introduced. The method, referred to as reliability-centred asset maintenance method (RCAM) is being developed within a research group at KTH in Sweden. Finally the presentation comments on ongoing research to evaluate the introduction of RCM. The aim of RCM is to optimize the maintenance achievements in a systematic way.

  • 17.
    Bertling, Lina M.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Allan, R.
    Eriksson, Roland
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    A reliability-centered asset maintenance method for assessing the impact of maintenance in power distribution systems2005Ingår i: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 20, nr 1, s. 75-82Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper proposes a method for comparing the effect of different maintenance strategies on system reliability and cost. This method relates reliability theory with the experience gained from statistics and practical knowledge of component failures and maintenance measures. The approach has been applied to rural and urban distribution systems. In particular, a functional relationship between failure rate and maintenance measures has been developed for a cable component. The results show the value of using a systematic quantitative approach for investigating the effect of different maintenance strategies.

  • 18.
    Bertling, Lina M.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Allan, R
    Eriksson, Roland
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    A reliability-centred asset maintenance method for assessing the impact of maintenance in power distribution systems2005Ingår i: 2005 IEEE Power Engineering Society General Meeting, 2005, s. 2649-2649Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper proposes a method for comparing the effect of different maintenance strategies on system reliability and cost. This method relates reliability theory with the experience gained from statistics and practical knowledge of component failures and maintenance measures. The approach has been applied to rural and urban distribution systems. In particular, a functional relationship between failure rate and maintenance measures has been developed for a cable component. The results show the value of using a systematic quantitative approach for investigating the effect of different maintenance strategies.

  • 19.
    Bertling, Lina
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Wallnerström, Carl Johan
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Nätnyttomodellens tillförlitlighet med avseende på små förändringar i indata2006Rapport (Övrigt vetenskapligt)
  • 20.
    Bertling Tjernberg, Lina
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    The Smart Grid Experience in Europe2014Övrigt (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    The development of a Smart Grid in Europe has a strong link to the climate goals for sustainable energy systems. Europe has been at the forefront of smart grid deployments, especially in the areas of managing large penetrations of renewable sources of energy, advanced metering infrastructure (AMI) and on advanced information technology. 

  • 21. Besnard, Francois
    et al.
    Bertling, Lina
    An approach for condition-based maintenance optimization applied to wind turbine blades2010Ingår i: IEEE Transactions on Sustainable Energy, ISSN 1949-3029, Vol. 1, nr 2, s. 77-83Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A sound maintenance planning is of crucial importance for wind power systems. There is a large potential in cost savings by optimizing maintenance decisions to make the projects more cost-efficient. This paper presents an approach to optimize condition-based maintenance strategies for components which degradation can be classified according to the severity of the damage. The approach is applicable to inspection-based maintenance as well as maintenance based on online condition-monitoring systems. This enables us to compare the maintenance strategies within a unified framework. First decisions associated with the different maintenance strategies are optimized, then the expected life cycle maintenance costs of the strategies are compared. The model is applied to blades of wind turbine in order to compare three maintenance strategies: visual inspection, inspection with a condition-monitoring technique (e.g., ultrasonic or thermography), and online condition monitoring (e.g., fiber optic). It is shown that online condition monitoring is the optimal maintenance strategy for high failure rate and low crack time to failure. In other cases, inspection with condition-based maintenance is slightly more beneficial. © 2010 IEEE.

  • 22.
    Besnard, Francois
    et al.
    KTH, Skolan för elektro- och systemteknik (EES).
    Nilsson, Julia
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Bertling, Lina
    On the economic benefits of using condition monitoring systems for maintenance management of wind power systems2010Ingår i: 2010 IEEE 11th International Conference on Probabilistic Methods Applied to Power Systems, PMAPS 2010, 2010, s. 160-165Konferensbidrag (Refereegranskat)
    Abstract [en]

    The large growth in the wind power industry in the past years mainly focuses on a growing market and the development of large turbines and offshore farms. The high technical availability of wind turbines comes with a high need for frequent maintenance. Current maintenance planning is generally not optimized, and it is possible to make maintenance more efficient. Condition Monitoring Systems (CMS) are commonly used in other industries and can reduce the consequential damage at failure and provides advantages for the planning of the maintenance. It is of interest to determine if the wind industry would benefit of the use of CMS. This paper shows results from Life-Cycle-Cost (LCC) evaluated with probabilistic methods and sensitivity analysis to identify the benefit of using CMS. The results highlight that there is a high economic benefit of using CMS, as well as benefits on the risk. The benefit is highly influenced by the reliability of the gearbox.

  • 23.
    Besnard, Francois
    et al.
    KTH, Skolan för elektro- och systemteknik (EES).
    Patriksson, Michael
    Strömberg, Ann-Brith
    Wojciechowski, Adam
    Bertling, Lina
    An Optimization Framework for Opportunistic Maintenance of Offshore Wind Power System2009Ingår i: 2009 IEEE BUCHAREST POWERTECH, VOLS 1-5 / [ed] Toma L; Otomega B, NEW YORK: IEEE , 2009, s. 2970-2976Konferensbidrag (Refereegranskat)
    Abstract [en]

    A sound maintenance planning is of crucial importance for wind power farms, and especially for offshore locations. There is a large potential in cost savings by maintenance optimization to make the projects more cost-efficient. This paper presents an opportunistic maintenance optimization model for offshore wind power system. The model takes advantage of wind forecasts and corrective maintenance activities in order to perform preventive maintenance tasks at low costs. The approach is illustrated with an example to demonstrate the value of the optimization. In this example 43% of the cost to perform preventive maintenance could be saved using the proposed method.

  • 24. Billinton, R.
    et al.
    Fotuhi-Firuzabad, M.
    Bertling, Lina M.
    KTH, Tidigare Institutioner                               , Elkraftteknik.
    Bibliography on the application of probability methods in power system reliability evaluation 1996-19992001Ingår i: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 16, nr 4, s. 595-602Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents a bibliography of papers on the subject of power system reliability evaluation. Papers in such areas as: probabilistic load flow, probabilistic production costing, probabilistic transient stability evaluation etc. have not been included except where they specifically address power system reliability evaluation. It includes material which has been made available since the publication of six previous papers Bibliography on the Application of Probability Methods in Power System Reliability Evaluation, IEEE Transactions on Power Apparatus and Systems PAS-91, 1972, pp. 649-660, Pas-97, 1978, pp. 2235-2242, PAS-103, 1984, pp. 275-282, IEEE Transactions on Power Systems, Vol. 3, no. 4, Nov. 1988, pp. 1555-1564, Vol. 9, No. 1, Feb. 1994, pp. 41-49, and Vol. 14, no. 1, Feb. 1999, pp. 51-57.

  • 25. Chowdhury, A. A.
    et al.
    Bertling, Lina
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Distribution system in-depth causal reliability assessment2006Ingår i: 2006 International Conference on Probabilistic Methods Applied to Power Systems, Vols 1 and 2, NEW YORK: IEEE , 2006, s. 805-812Konferensbidrag (Refereegranskat)
    Abstract [en]

    The methodology used to assess the historical reliability performance of a Canadian Utility's electric distribution system is outlined. Included is an overview of the process used to collect and organize the required interruption data as well as a description of the performance indices calculated for use in the causal assessment. The various component parts of the reliability performance assessment are described. This includes a description of indices comparison between years and to the average at different levels of the system and by outage cause and component failure. Finally, results from the 2004 reliability assessment of the utility's electric distribution system are summarized and the application of the calculated performance statistics in planning, operating and maintaining distribution systems is described.

  • 26.
    Chowdhury, A. A.
    et al.
    MidAmer Energy Co, Elect Syst Planning, Davenport, IA 52801 USA..
    Bertling, Lina
    KTH. Royal Inst Technol, Stockholm, Sweden..
    Glover, B. P.
    Mid Continent Area Power Pool, St Paul, MN USA..
    Causal and seasonal analysis of bulk transmission lineforced outages using the MAPP outage database2006Ingår i: 2006 INTERNATIONAL CONFERENCE ON PROBABILISTIC METHODS APPLIED TO POWER SYSTEMS, VOLS 1 AND 2, IEEE , 2006, s. 819-825Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper describes the Mid-Continent Area Power Pool (MAPP) transmission equipment outage data collection scheme and presents bulk transmission line average outage statistics for forced outage category for the 230 kV and above systems computed using the data for the ten-year operating period from 1991 to 2000. In addition, a causal and seasonal contribution to forced outages of bulk transmission line is analyzed that helps to identify appropriate remedial actions to improve transmission line reliability. This paper presents selected applications of transmission line forced outage statistics by different MAPP member utilities.

  • 27. Chowdhury, A. A.
    et al.
    Bertling, Lina
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Glover, B. P.
    Haringa, G. E.
    Monte Carlo simulation model for multi-area generation reliability evaluation2006Ingår i: 2006 International Conference on Probabilistic Methods Applied to Power Systems, Vols 1 and 2, NEW YORK: IEEE , 2006, s. 1216-1225Konferensbidrag (Refereegranskat)
    Abstract [en]

    Power system reliability assessment methods can be categorized either analytical or as Monte Carlo simulation. Analytical methods represent the power system by a mathematical model and assess the reliability performance indices from the model utilizing mathematical solutions. On the other hand, Monte Carlo simulation methods, compute the reliability indices by simulating the actual process and random behavior of the power system, and can include any system effects or system processes which may have to be approximated in analytical methods. This paper describes a Monte Carlo simulation tool, which has been developed by General Electric (GE) Company for the reliability analysis of multi-area generation systems with explicit recognition of those unit and system operating considerations, rules, and constraints that influence system reliability indices. The basic features, capabilities and applications of the Monte Carlo simulation model are illustrated using the Mid-Continent Area Power Pool (MAPP) interconnected system reserve capacity obligation (RCO) study in this paper.

  • 28. Chowdhury, A. A.
    et al.
    Bertling, Lina M.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Custer, D. E.
    Determining distribution substation transformer optimal loadings using a reliability cost-benefit approach2006Ingår i: 2006 International Conference on Probabilistic Methods Applied to Power Systems, Vols 1 and 2, NEW YORK: IEEE , 2006, s. 1201-1209Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a novel reliability cost-benefit approach, taking into account customer value of reliability, to compare different transformer loading philosophies while concurrently considering varying levels of transformer emergency capability. Using this cost benefit approach, guidelines for loading existing transformers can be determined. The developed methodology can also be used to establish standard emergency rating criteria for purchasing new transformers, which will optimize reliability performance versus cost. The methodology is illustrated using practical system examples.

  • 29. Chowdhury, A. A.
    et al.
    Bertling, Lina M.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Glover, B. P.
    Causal and seasonal analysis of bulk transmission line forced outages using the MAPP outage database2006Ingår i: 2006 International Conference on Probabilistic Methods Applied to Power Systems, NEW YORK: IEEE , 2006, s. 847-853Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    This paper describes the Mid-Continent Area Power Pool (MAPP), transmission equipment outage data collection scheme and presents bulk transmission line average outage statistics for forced outage category for the 230 kV and above systems computed using the data for the ten-year operating period from 1991 to 2000. In addition, a causal and seasonal contribution to forced outages of bulk transmission line is analyzed that helps to identify appropriate remedial actions to improve transmission line reliability. This paper presents selected applications of transmission line forced outage statistics by different MAPP member utilities.

  • 30.
    Cui, Yue
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknisk teori och konstruktion.
    Bangalore, Pramod
    Greenbyte AB, Gothenburg, Sweden.
    Bertling Tjernberg, Lina
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknisk teori och konstruktion.
    An anomaly detection approach based on machine learning and scada data for condition monitoring of wind turbines2018Ingår i: 2018 International Conference on Probabilistic Methods Applied to Power Systems, PMAPS 2018 - Proceedings, Institute of Electrical and Electronics Engineers Inc. , 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents an anomaly detection approach using machine learning to achieve condition monitoring for wind turbines. The approach applies the information in supervisory control and data acquisition systems as data input. First, machine learning is used to estimate the temperature signals of the gearbox component. Then the approach analyzes the deviations between the estimated values and the measurements of the signals. Finally, the information of alarm logs is integrated with the previous analysis to determine the operation states of wind turbines. The proposed approach has been tested with the data experience of a 2MW wind turbine in Sweden. The result demonstrates that the approach can detect possible anomalies before the failure occurrence. It also certifies that the approach can remind operators of the possible changes inside wind turbines even when the alarm logs do not report any alarms.

  • 31.
    Cui, Yue
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknisk teori och konstruktion.
    Bangalore, Pramod
    Greenbyte AB, Gothenburg, Sweden..
    Bertling Tjernberg, Lina
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknisk teori och konstruktion.
    An Anomaly Detection Approach Using Wavelet Transform and Artificial Neural Networks for Condition Monitoring of Wind Turbines' Gearboxes2018Ingår i: 2018 POWER SYSTEMS COMPUTATION CONFERENCE (PSCC), IEEE , 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents an anomaly detection approach using artificial neural networks and the wavelet transform for the condition monitoring of wind turbines. The method aims to attain early anomaly detection and to prevent possible false alarms under healthy operations. In the approach, nonlinear autoregressive neural networks are used to estimate the temperature signals of the gearbox. The Mahalanobis distances are then calculated to measure the deviations between the current states and healthy operations. Next, the wavelet transform is applied to remove noisy signals in the distance values. Finally, the operation information is considered together with the refined distance values to detect potential anomalies. The proposed approach has been tested with the real data of three 2 MW wind turbines in Sweden. The results show that the approach can detect possible anomalies before failure events occur and avoid reporting alarms under healthy operations.

  • 32. Endrenyi, J.
    et al.
    Anders, G. J.
    Bertling, Lina
    KTH, Tidigare Institutioner, Elektrotekniska system.
    Kalinowski, B.
    Comparison of two methods for evaluating the effects of maintenance on component and system reliability2004Ingår i: 2004 International Conference on Probabilistic Methods Applied to Power Systems, 2004, s. 307-312Konferensbidrag (Refereegranskat)
    Abstract [en]

    Two recently proposed methods for evaluating the effects of various maintenance policies on the reliability and operating costs of electric power systems are compared. Both programs, the one developed in Canada and the other in Sweden, first generate a priority list of components whose failures have the highest effect on system reliability, then examine the failure rates of the components on the top of the list when various maintenance policies are applied. Finally, reliability indices for the whole system are computed with the critical components represented by the failure rates corresponding to the various policies. This way, maintenance policies can be selected either to achieve the highest system reliability or the lowest operating costs. The approach is illustrated in a numerical example where both the similarities of, and the differences between, the two methods can be recognized. Comments are made on the reasons for the differences.

  • 33.
    Eriksson, Roland
    et al.
    KTH, Tidigare Institutioner                               , Elektrotekniska system.
    Lindquist, Tommie
    KTH, Tidigare Institutioner                               , Elektrotekniska system.
    Bertling, Lina
    KTH, Tidigare Institutioner                               , Elektrotekniska system.
    Reliability modelling of aged XLPE cables2003Ingår i: Nordic Insulation Symposium (Nord-Is), 2003, s. 216-224Konferensbidrag (Refereegranskat)
  • 34.
    Feng, Wang
    et al.
    Chalmers, Div Elect Power Engn, S-41296 Gothenburg, Sweden.
    Tuan, Le
    Chalmers, Div Elect Power Engn, S-41296 Gothenburg, Sweden.
    Bertling Tjernberg, Lina
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion. Chalmers, Div Elect Power Engn, S-41296 Gothenburg, Sweden.
    Mannikoff, Anders
    SP Technical Research Institute of Sweden, Borås 501 15, Sweden.
    Bergman, Anders
    SP Tech Res Inst Sweden, S-50115 Boras, Sweden.
    A New Approach for Benefit Evaluation of Multiterminal VSC–HVDC Using A Proposed Mixed AC/DC Optimal Power Flow2014Ingår i: IEEE Transactions on Smart Grid, ISSN 1949-3053, E-ISSN 1949-3061, ISSN 1949-3053, Vol. 29, nr 1, s. 432-443Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, an extended optimal power-flow (OPF) model incorporating a detailed model of a voltage-source con- verter-based–multiterminal high-voltage direct current system (VSC–MTDC) is proposed, hereafter referred to as the mixed ac/dc OPF (M-OPF) model. A cost-benefit analysis approach using the M-OPF model as the calculation engine is proposed to determine the preferred VSC-MTDC alternative to be installed in an existing ac transmission system. In this approach, the op- erational benefits of VSC–MTDC systems are evaluated against their investment costs to derive the benefit-to-cost ratios (BCR) which reflect the cost-effectiveness of the alternatives. A case study has been carried out using a modified Nordic 32-bus system. The results of the study show that VSC–MTDC systems might lead to a reduction in total operation cost, and the reduction of the total system transmission loss depends to a large extent on the VSC–MTDC configuration. The results from sensitivity analyses show that if the VSC loss could be reduced to a third of the original level, the total benefit from the system would be increased by about 70%. A suggestion for the placement and configuration of a VSC–MTDC system is made based on calculated BCRs. 

  • 35.
    Hilber, Patrik
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Bertling, Lina
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    A Method for Extracting Reliability Importance Indices from Reliability Simulations of Electrical Networks2005Ingår i: 15th Power Systems Computation Conference, PSCC 2005, Power Systems Computation Conference ( PSCC ) , 2005Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper proposes a reliability importance index that is possible to extract from existing reliability simulations at a low additional computational cost. The index utilizes the concept of reliability worth as a measure of system reliability in order to establish the importance of components in systems with several load points. Since the method is based on simulations, it is suitable for large networks with a high level of detail. The index can be used as decision support for asset management, for example where maintenance actions will become most beneficial. The index is evaluated against the background of a number of analytically calculated indices. Furthermore, the index is applied to a network in the Stockholm area. The conclusion of the paper is that the proposed simulation based importance index provides a means of improving analysis of electrical network reliability.

  • 36.
    Hilber, Patrik
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Bertling, Lina
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Component Reliability Importance Indices for Electrical Networks2007Ingår i: 2007 CONFERENCE PROCEEDINGS IPEC, VOLS 1-3, NEW YORK: IEEE , 2007, s. 257-263Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents three new component reliability importance indices, developed for electrical networks. Component reliability importance indices are useful for prioritization of components as part of a system, especially when considering maintenance activities and/or investment in new equipment. Traditional component reliability importance indices were developed for systems with one input and one output point, which not captures the general function of electrical networks. The proposed indices utilize the concept of reliability worth as a single measure of system reliability in order to establish the importance of the components. This single measure of reliability works over several supply and load points and does for example enable comparisons between components decicated to different load points as well as components from different systems. Furthermore this paper presents data from application studies, which shows on some of the possibilities with the indices. The conclusion of the paper is that the proposed indices provide means of improving analysis of electrical network reliability.

  • 37.
    Hilber, Patrik
    et al.
    KTH, Tidigare Institutioner, Elektrotekniska system.
    Bertling, Lina
    KTH, Tidigare Institutioner, Elektrotekniska system.
    Monetary Importance of Component Reliability in Electrical Networks for Maintenance Optimization2004Ingår i: 8th International Conference on Probabilistic Methods Applied to Power Systems: Iowa State Univ, Ames, IA, SEP 12-16, 2004, 2004, s. 150-155Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper proposes a method for defining the importance of individual components in a network with respect to total interruption cost. Since the method considers several customer nodes simultaneously, it is especially suitable for network structures that serve many purposes/customers e.g. transmission and distribution networks with more than one load point. The major result is an importance index, I-H, for every component. This index can be used for the evaluation of maintenance actions. Furthermore, the importance index is used to calculate the component contribution to the total system interruption cost. Finally, the goal to reach an optimal maintenance plan is outlined. The methodology is presented together with an application study for an electrical distribution system in-the Stockholm area.

  • 38.
    Hilber, Patrik
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Bertling, Lina
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Multiobjective Maintenance Policy for a Distribution System an Application Study2008Ingår i: 10th International Conference On Probabilistic Methods Applied To Power Systems, 2008, s. 229-234Konferensbidrag (Refereegranskat)
    Abstract [en]

    Maintenance managers of today's electrical distribution systems are faced with the problem of where their maintenance resources will be utilized best. In previous work the authors have developed a method for maintenance policy optimization for electrical networks. This paper presents results from an application study performed for a distribution system, including both urban and rural parts, for this method. A basic optimization is performed in order to find the right level of maintenance for the involved components with respect to customer interruption costs and maintenance budget. For the rural parts of the system the conclusion is that intensified tree trimmings is the most beneficial maintenance activity. While for the urban parts the maintenance should be focused towards customer intense areas. Furthermore, it becomes clear, especially for the urban part of the system, that the operation mode of the network becomes important. The method presented helps the managers to prioritize their maintenance to the places where it will result in the best system performance.

  • 39.
    Hilber, Patrik
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Bertling, Lina
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Hällgren, Bengt
    Karlstads Universitet.
    Effects of Correlation between Failures and Power Consumption on Customer Interruption Cost2006Ingår i: 2006 International Conference on Probabilistic Methods Applied to Power Systems, Vols 1 and 2: 9th International Conference on Probabilistic Methods Applied to Power Systems. KTH, Stockholm, SWEDEN. JUN 11-15, 2006, 2006, s. 1120-1123Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper evaluates the correlation between failures and power consumption for a distribution systems operator. This is done in order to scrutinize whether the commonly used assumptions of constant failure rate and constant power consumption is reasonable to use for reliability calculations. The studied entity is energy not supplied, which is assumed to be a good estimate of how customer interruption costs are affected. Three different aspects are studied with respect to energy not supplied; seasonal variations, daily variations and repair time variations (as a function of the hour of day). The conclusion is that by using constant failure rates, repair rates and power consumption the approximation of customer costs becomes somewhat low, i.e. by 7% for the studied case. This result indicates that the assumptions of constant failure rates, repair rates and power consumption are quite sufficient for at least the actual case study. Le. since this error probably is significantly smaller than other types of errors, for example customer outage costs estimates. Nevertheless, having performed these calculations the current results should be applied to further modeling of the studied network.

  • 40.
    Hilber, Patrik
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Hällgren, Bengt
    Karlstads Universitet.
    Bertling, Lina
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Optimizing the replacement of overhead lines in rural distribution systems with respect to reliability and customer value2005Ingår i: Eighteenth International Conference and Exhibition on Electricity Distribution, CIRED 2005, 2005, s. 127-131Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper we present a method for establishing the value of a network's components from a reliability worth perspective. The method can be applied to a general distribution system i.e. both for radial and meshed network systems. Moreover, this paper shows results from an application study for a rural network system that is dominated by overhead lines. The purpose of the study was to establish the value of a secondary feeding point. Further, the method is used to establish the best replacement strategy for the concerned overhead lines.

  • 41.
    Hilber, Patrik
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Miranda, Vladimiro
    Faculty of Engineering, University of Porto.
    Matos, Manuel A.
    Faculty of Engineering, University of Porto.
    Bertling, Lina
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Multiobjective Optimization Applied to Maintenance Policy for Electrical Networks2007Ingår i: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 22, nr 4, s. 1675-1682Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A major goal for managers of electric power networks is maximum asset performance. Minimal life cycle cost and maintenance optimization becomes crucial in reaching this goal, while meeting demands from customers and regulators. This necessitates the determination of the optimal balance between preventive and corrective maintenance in order to obtain the lowest total cost.

    The approach of this paper is to study the problem of balance between preventive and corrective maintenance as a multiobjective optimization problem, with customer interruptions on one hand and the maintenance budget of the network operator on the other. The problem is solved with meta-heuristics developed for the specific problem, in conjunction with an evolutionary particle swarm optimization algorithm.

    The maintenance optimization is applied in a case study to an urban distribution system in Stockholm, Sweden. Despite a general decreased level of maintenance (lower total maintenance cost), better network performance can be offered to the customers. This is achieved by focusing the preventive maintenance on components with a high potential for improvements. Besides this, this paper displays the value of introducing more maintenance alternatives for every component and choosing the right level of maintenance for the components with respect to network performance.

  • 42.
    Leelaruji, Rujiroj
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Setréus, Johan
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Olguin, Gabriel
    Bertling, Lina
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Availability Assessment of the HVDC Converter Transformer System2008Ingår i: Proceedings of the 10th International Conference on Probabilistic Methods Applied to Power Systems, PMAPS 2008, New York: IEEE , 2008, s. 575-582Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a reliability assessment of the HVDC converter transformer system (CTS) comparing different component models and configurations. The CTS model is based on the Markov modelling approach, which is shown to be well suited for these relatively small systems. The failure rate data in the models is based on statistical surveys by CIGRE. A number of scenarios are calculated in order to evaluate the impact of the availability of the CTS given different conditions. The result shows on the benefit in availability using a spare transformer, particularly at a close location of the HVDC station.

  • 43.
    Lindquist, Tommie
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Bertling, Lina
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    A method for calculating disconnector contact availability as a function of thermography inspection intervals and load current2007Ingår i: CIGRE Symposium Osaka 2007: System Development and Asset Management under Restructuring, 2007Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a practical method of quantifying and evaluating changes to existing thermography inspection schemes for disconnector contacts. The inspection interval availability is used to calculate disconnector contact average maintenance costs. Any changes to existing thermography schemes regarding load or inspection intervals are subsequently evaluated using these maintenance costs. The proposed method is illustrated by a case study of three disconnectors in the Swedish 400-220kV transmission system. The three disconnectors represent different typical load characteristics. The result of the case study was that the new thermography inspection scheme would reduce the total average maintenance cost by a third, for the three disconnectors. In the study, the large reduction in maintenance cost was due to the specific load characteristics of the disconnectors. When applying the method to a larger disconnector population the cost reduction would depend on the actual loading characteristics of all disconnectors. The aim of the case study is to illustrate the usefulness of the proposed method when it comes to quantifying the effect of changes in thermography inspection schemes. The only failure mode considered in this paper is contact over-heating. A disconnector contact that is found to be failed is assumed to be replaced by a new identical contact. Since the exact time of a hidden failure is unknown, the exponential distribution is used for the time to failure in order to adapt the model to the amount of information available to the network owner. The proposed method provides a practical tool to quantify and evaluate the effect of different changes to the inspection scheme with respect to maintenance costs and availability.

  • 44.
    Lindquist, Tommie
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Bertling, Lina
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Hazard rate estimation for high-voltage contacts using infrared thermography2008Ingår i: Proceedings. Annual Reliability and Maintainability Symposium, ISSN 0149-144X, s. 233-239Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Infrared thermography is the most common way to assess the condition of high-voltage electrical contacts in electric distribution and transmission systems. However, thermography has one major drawback as contacts carrying low or no load may not be assessed.

    This paper proposes a method to save and make use of thermography measurements to estimate statistical distribution parameters for the time to failure for a population of electrical contacts. The statistical distributions may then be used to support maintenance decisions for the sometimes large proportion of contacts that may not be assessed directly due to low load. As the measurement results accumulate over the years more accurate predictions can be made.

    The proposed method is illustrated using three test cases applied to a population of high-voltage disconnectors with randomly generated thermography measurements.

    The main conclusion of the paper is that using the proposed method will provide maintenance decision support for high-voltage apparatus that may not be assessed directly by thermography.

  • 45.
    Lindquist, Tommie
    et al.
    KTH, Tidigare Institutioner, Elektrotekniska system.
    Bertling, Lina
    KTH, Tidigare Institutioner, Elektrotekniska system.
    Eriksson, Roland
    KTH, Tidigare Institutioner, Elektrotekniska system.
    A feasibility study for probabilistic modeling of aging in circuit breakers for maintenance optimization2004Ingår i: 2004 INTERNATIONAL CONFERENCE ON PROBABILISTIC METHODS APPLIED TO POWER SYSTEMS, NEW YORK: IEEE , 2004, s. 1020-1025Konferensbidrag (Refereegranskat)
    Abstract [en]

    To support the maintenance optimization carried out within the framework of the reliability-centered asset management (RCAM) method this paper presents a feasibility study for the probabilistic modeling of the aging of circuit-breakers (CB). The aim of the study is to investigate the possibilities of the development of a reliability model for a CB, using failure data and maintenance records. A study of such statistics was carried out on all 565 CBS in the Swedish National Grid (transmission level) during a time period ranging from 1999-01-01 to 2003-06-30. A total of 53 CB failures were identified and studied with respect to faulty subcomponent, CB function, number of operating cycles to failure and time in operation to failure. Results from this study are presented in this paper.

  • 46.
    Lindquist, Tommie
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Bertling, Lina
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Eriksson, Roland
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    A method for age modeling of power system components based on experiences from the design process with the purpose of maintenance optimization2005Ingår i: Proceedings. Annual Reliability and Maintainability Symposium, ISSN 0149-144X, s. 82-88Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper introduces a first step towards establishing the effect of maintenance on component reliability. The concept of relative age is introduced and defined as well as a method to establish this relative age of electric power system components for the purpose of maintenance optimization. The proposed method is demonstrated by modeling the relative age of a sub-component for a circuit breaker (CB). The modeling is based on the results from a major CB reliability study and a survey of all CB failures in the Swedish National Grid during the period from January 1(st), 1999 to July 31(st), 2003. The results from this application study show that it is possible to model the reliability of power system components by using results from development tests and calculations from the design process along with failure and maintenance data.

  • 47.
    Lindquist, Tommie
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Bertling, Lina
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Eriksson, Roland
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    A practical method for benefit/cost analysis of preventive maintenance tasks in power system equipment2007Ingår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208Artikel i tidskrift (Övrigt vetenskapligt)
  • 48.
    Lindquist, Tommie
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Bertling, Lina
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Eriksson, Roland
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Circuit breaker failure data and reliability modelling2008Ingår i: IET Generation, Transmission and Distribution, ISSN 1751-8687, Vol. 2, nr 6, s. 813-820Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The results from an extensive study of SF6 and minimum-oil circuit breaker failures in the Swedish and Finnish transmission systems are presented. The study includes 1546 breakers with a total operating history of 16 384 years. In the study, a detailed analysis of a specific SF6 type of breaker revealed which parts caused the failures and an estimation of their hazard rates was made. A model of complete reliability for this type of breaker is presented, illustrated by presenting the operating and maintenance history of a shunt reactor breaker in the Swedish transmission system.

  • 49.
    Lindquist, Tommie
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Bertling, Lina
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Eriksson, Roland
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Estimation of disconnector contact condition for modelling the effect of maintenance and ageing2005Ingår i: 2005 IEEE Russia Power Tech, PowerTech, 2005Konferensbidrag (Refereegranskat)
    Abstract [en]

    In order to optimize the maintenance of electric power equipment, models of equipment reliability as a function of age and maintenance are necessary. As a first step towards the development of these kinds of models, this paper proposes a quantitative method for establishing the condition of disconnector contacts by the use of thermography, which is a well-established diagnostic practice used in preventive maintenance programmes. Results from two sets of thermography measurements carried out in the Swedish transmission grid are presented. Statistical distributions for the uncertainties when using the method are estimated from the measurements. A method for converting temperature rises measured at non steady state loading conditions to a corresponding steady state temperature rise have been devised using a simple thermal model. The probability of sending an unaged contact to maintenance is estimated using Monte Carlo simulations based on the statistical distributions of the uncertainties. Finally, it is shown that by using the method proposed in this paper it is possible to estimate the contact condition of disconnectors, including Monte Carlo simulated confidence intervals.

  • 50.
    Mazidi, Peyman
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Bertling, Lina
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Sanz-Bobi, Miguel A.
    Performance Analysis and Anomaly Detection in Wind Turbines based on Neural Networks and Principal Component Analysis2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper proposes an approach for maintenancemanagement of wind turbines based on their life. The proposedapproach uses performance analysis and anomaly detection(PAAD) which can detect anomalies and point out the originof the detected anomalies. This PAAD algorithm utilizes neuralnetwork (NN) technique in order to detect anomalies in theperformance of the wind turbine (system layer), and then appliesprincipal component analysis (PCA) technique to uncover theroot of the detected anomalies (component layer). To validatethe accuracy of the proposed algorithm, SCADA data obtainedfrom online condition monitoring of a wind turbine are utilized.The results demonstrate that the proposed PAAD algorithm hasthe capability of exposing the cause of the anomalies. Reducingtime and cost of maintenance and increasing availability and inreturn profits in form of savings are some of the benefits of theproposed PAAD algorithm.

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