| 1. |
- Bertling, Lina, et al.
(författare)
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RADPOW development and documentation
- 2008
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Rapport (populärvet., debatt m.m.)abstract
- 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.
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| 2. |
- Hilber, Patrik, et al.
(författare)
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A Method for Extracting Reliability Importance Indices from Reliability Simulations of Electrical Networks
- 2005
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Ingår i: 15th Power Systems Computation Conference, PSCC 2005. - : Power Systems Computation Conference ( PSCC ).
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 3. |
- Hilber, Patrik, et al.
(författare)
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Component Reliability Importance Indices for Electrical Networks
- 2007
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Ingår i: 2007 CONFERENCE PROCEEDINGS IPEC, VOLS 1-3. - NEW YORK : IEEE. - 9789810594237 ; , s. 257-263
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 4. |
- Hilber, Patrik, 1975-
(författare)
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Component reliability importance indices for maintenance optimization of electrical networks
- 2005
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Maximum asset performance is one of the major goals for electric power system managers. To reach this goal minimal life cycle cost and maintenance optimization become crucial while meeting demands from customers and regulators. One of the fundamental objectives is therefore to relate maintenance and reliability in an efficiently and effectively way, which is the aim of several maintenance methods such as the Reliability Centered Maintenance method (RCM). Furthermore, this necessitates the determination of the optimal balance between preventive and corrective maintenance to obtain the lowest total cost. This thesis proposes methods for defining the importance of individual components in a network with respect to total interruption cost. This is a first step in obtaining an optimal maintenance solution. Since the methods consider several customer nodes simultaneously, they are especially suitable for network structures that serve many purposes/customers e.g. transmission and distribution networks with more than one load point. The major results are three component reliability importance indices, which are applied in two case studies. The first case study is based on a network in the Stockholm area. The second case study is performed for one overhead line system in the rural parts of Kristinehamn. The application studies demonstrate that the indices are possible to implement for existing electrical networks and that they can be used for maintenance prioritization. Consequently these indices constitute a first step in the overall objective of a maintenance optimization method. The computations of the indices are performed both with analytical and simulation based techniques. Furthermore, the indices can be used to calculate the component contribution to the total system interruption cost. The approach developed for the importance indices can be utilized in any multi-state network that can be measured with one performance indicator.
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| 5. |
- Hilber, Patrik, et al.
(författare)
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Effects of Correlation between Failures and Power Consumption on Customer Interruption Cost
- 2006
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Ingår i: 2006 International Conference on Probabilistic Methods Applied to Power Systems, Vols 1 and 2. - 9789171785855 ; , s. 1120-1123
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 6. |
- Hilber, Patrik, 1975-
(författare)
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Maintenance optimization for power distribution systems
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Maximum asset performance is one of the major goals for electric power distribution system operators (DSOs). To reach this goal minimal life cycle cost and maintenance optimization become crucial while meeting demands from customers and regulators. One of the fundamental objectives is therefore to relate maintenance and reliability in an efficient and effective way. Furthermore, this necessitates the determination of the optimal balance between pre¬ventive and corrective maintenance, which is the main problem addressed in the thesis. The balance between preventive and corrective maintenance is approached as a multiobjective optimization problem, with the customer interruption costs on one hand and the maintenance budget of the DSO on the other. Solutions are obtained with meta-heuristics, developed for the specific problem, as well as with an Evolutionary Particle Swarm Optimization algorithm. The methods deliver a Pareto border, a set of several solutions, which the operator can choose between, depending on preferences. The optimization is built on component reliability importance indices, developed specifically for power systems. One vital aspect of the indices is that they work with several supply and load points simultaneously, addressing the multistate-reliability of power systems. For the computation of the indices both analytical and simulation based techniques are used. The indices constitute the connection between component reliability performance and system performance and so enable the maintenance optimization. The developed methods have been tested and improved in two case studies, based on real systems and data, proving the methods’ usefulness and showing that they are ready to be applied to power distribution systems. It is in addition noted that the methods could, with some modifications, be applied to other types of infrastructures. However, in order to perform the optimization, a reliability model of the studied power system is required, as well as estimates on effects of maintenance actions (changes in failure rate) and their related costs. Given this, a generally decreased level of total maintenance cost and a better system reliability performance can be given to the DSO and customers respectively. This is achieved by focusing the preventive maintenance to components with a high potential for improvement from system perspective.
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| 7. |
- Hilber, Patrik, et al.
(författare)
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Multiobjective Maintenance Policy for a Distribution System an Application Study
- 2008
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Ingår i: 10th International Conference On Probabilistic Methods Applied To Power Systems. - 9781934325216 ; , s. 229-234
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 8. |
- Hilber, Patrik, et al.
(författare)
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Multiobjective Optimization Applied to Maintenance Policy for Electrical Networks
- 2007
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Ingår i: IEEE Transactions on Power Systems. - 0885-8950 .- 1558-0679. ; 22:4, s. 1675-1682
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 9. |
- Hilber, Patrik, et al.
(författare)
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Optimizing the replacement of overhead lines in rural distribution systems with respect to reliability and customer value
- 2005
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Ingår i: Eighteenth International Conference and Exhibition on Electricity Distribution, CIRED 2005. ; , s. 127-131
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Konferensbidrag (refereegranskat)abstract
- 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.
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