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Maintenance optimization for power distribution systems
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.ORCID iD: 0000-0002-2964-7233
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

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.

Place, publisher, year, edition, pages
Stockholm: KTH , 2008. , vii, 56 p.
Series
Trita-EE, ISSN 1653-5146 ; 2008:012
Keyword [en]
Reliability Importance Index, Multiobjective Optimization, Maintenance Optimization, Asset Management, Customer Interruption Cost, Reliability Centred Maintenance (RCM), Reliability Centered Asset Management (RCAM), Monte Carlo Simulation, Evolutionary Particle Swarm Optimization.
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-4686ISBN: 978-91-628-7464-3 (print)OAI: oai:DiVA.org:kth-4686DiVA: diva2:13421
Public defence
2008-04-18, D3, D, Lindstedsv. 5, Stockholm, 13:15
Opponent
Supervisors
Note
QC 20100810Available from: 2008-04-03 Created: 2008-04-03 Last updated: 2010-08-10Bibliographically approved
List of papers
1. Monetary Importance of Component Reliability in Electrical Networks for Maintenance Optimization
Open this publication in new window or tab >>Monetary Importance of Component Reliability in Electrical Networks for Maintenance Optimization
2004 (English)In: 8th International Conference on Probabilistic Methods Applied to Power Systems: Iowa State Univ, Ames, IA, SEP 12-16, 2004, 2004, 150-155 p.Conference paper, Published paper (Refereed)
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.

Keyword
maintenance; optimization; reliability; interruption cost; importance index; reliability-centered maintenance (RCM); reliability-centered asset management (RCAM)
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-8163 (URN)000225735200026 ()2-s2.0-14544273157 (Scopus ID)0-9761319-1-9 (ISBN)
Note

QC 20100810

Available from: 2008-04-03 Created: 2008-04-03 Last updated: 2017-06-14Bibliographically approved
2. Optimizing the replacement of overhead lines in rural distribution systems with respect to reliability and customer value
Open this publication in new window or tab >>Optimizing the replacement of overhead lines in rural distribution systems with respect to reliability and customer value
2005 (English)In: Eighteenth International Conference and Exhibition on Electricity Distribution, CIRED 2005, 2005, 127-131 p.Conference paper, Published paper (Refereed)
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.

Series
IEE Conference Publication, 2005-11034
Keyword
Electric power distribution; Reliability; Rural areas; Rural distribution systems; Rural network systems
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-8164 (URN)2-s2.0-28644436819 (Scopus ID)
Note
QC 20100810Available from: 2008-04-03 Created: 2008-04-03 Last updated: 2010-11-30Bibliographically approved
3. A Method for Extracting Reliability Importance Indices from Reliability Simulations of Electrical Networks
Open this publication in new window or tab >>A Method for Extracting Reliability Importance Indices from Reliability Simulations of Electrical Networks
2005 (English)In: 15th Power Systems Computation Conference, PSCC 2005, Power Systems Computation Conference ( PSCC ) , 2005Conference paper, Published paper (Refereed)
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.

Place, publisher, year, edition, pages
Power Systems Computation Conference ( PSCC ), 2005
Keyword
reliability importance index, Monte Carlo simulation, electrical network, customer interruption cost, reliability worth
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-8165 (URN)2-s2.0-84982318178 (Scopus ID)
Conference
15th Power Systems Computation Conference, PSCC 2005, Liege, Belgium, 22 August 2005 through 26 August 2005
Note

QC 20161121

Available from: 2008-04-03 Created: 2008-04-03 Last updated: 2016-11-21Bibliographically approved
4. Effects of Correlation between Failures and Power Consumption on Customer Interruption Cost
Open this publication in new window or tab >>Effects of Correlation between Failures and Power Consumption on Customer Interruption Cost
2006 (English)In: 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, 1120-1123 p.Conference paper, Published paper (Refereed)
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.

Keyword
failure rate; interruption cost; repair rate; reliability
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-8166 (URN)10.1109/PMAPS.2006.360419 (DOI)000246355900174 ()2-s2.0-46149086567 (Scopus ID)978-91-7178-585-5 (ISBN)
Note
QC 20100810Available from: 2008-04-03 Created: 2008-04-03 Last updated: 2011-10-05Bibliographically approved
5. Multiobjective Optimization Applied to Maintenance Policy for Electrical Networks
Open this publication in new window or tab >>Multiobjective Optimization Applied to Maintenance Policy for Electrical Networks
2007 (English)In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 22, no 4, 1675-1682 p.Article in journal (Refereed) Published
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.

Keyword
asset management; component reliability importance; maintenance; multiobjective optimization; power distribution systems
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-8167 (URN)10.1109/TPWRS.2007.908468 (DOI)000250559200030 ()2-s2.0-36348973029 (Scopus ID)
Note
QC 20100810Available from: 2008-04-03 Created: 2008-04-03 Last updated: 2017-12-14Bibliographically approved
6. Component Reliability Importance Indices for Electrical Networks
Open this publication in new window or tab >>Component Reliability Importance Indices for Electrical Networks
2007 (English)In: 2007 CONFERENCE PROCEEDINGS IPEC, VOLS 1-3, NEW YORK: IEEE , 2007, 257-263 p.Conference paper, Published paper (Refereed)
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.

Place, publisher, year, edition, pages
NEW YORK: IEEE, 2007
Keyword
asset management; component importance; maintenance; Monte Carlo simulation; optimization; reliability
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-8168 (URN)000257065300048 ()2-s2.0-51349093396 (Scopus ID)978-981-05-9423-7 (ISBN)
Conference
IPEC 2007 Meeting. Singapore, SINGAPORE. DEC 03-06, 2007
Available from: 2008-04-03 Created: 2008-04-03 Last updated: 2011-09-13Bibliographically approved
7. Multiobjective Maintenance Policy for a Distribution System an Application Study
Open this publication in new window or tab >>Multiobjective Maintenance Policy for a Distribution System an Application Study
2008 (English)In: 10th International Conference On Probabilistic Methods Applied To Power Systems, 2008, 229-234 p.Conference paper, Published paper (Refereed)
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.

Keyword
Asset management, Component reliability importance, Maintenance, Multiobjective optimization, Power distribution systems
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-8169 (URN)000271680900034 ()978-1-934325-21-6 (ISBN)
Note
QC 20100810Available from: 2008-04-03 Created: 2008-04-03 Last updated: 2011-03-01Bibliographically approved

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CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
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