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On reliability modelling of ageing equipment in electric power systems with regard to the effect of maintenance
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
2005 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

Power system maintenance optimisation involves obtaining the minimum total costs, including preventive and corrective maintenance costs and the cost of failures for both supplier and customer. To calculate the cost of failure, information is needed about the equipment reliability characteristics. It is also necessary to know how maintenance affects component reliability. The aim of the work leading up to this thesis has been to develop reliability models that include the effect of maintenance.

Three case studies have been carried out for different types of power system components using three distinct methods. In the first study the reliability of the first generation XLPE cables was modelled with respect to failures caused by water treeing using load-strength modelling. The model was based on assumptions of the ageing process and the distribution system characteristics. This study showed that it is possible to and overvoltage and insulation characteristics that can be fitted to agree with failure statistics for water tree ageing in XLPE cables. The second case study included a study of all circuit breaker failures in the Swedish transmission grid during the period from 1 January 1999 to 30 June 2003. In a subsequent investigation a method to combine information from the design process with maintenance records and failure statistics was employed using Bayesian methods. The resulting reliability model is continuously updated as more failure and maintenance data

becomes available. This case study showed that it is possible to develop reliability models for components that have not yet failed by utilising information from the design process and right-censored observations from inspections. Finally, in the third case study a quantitative method for establishing the condition of disconnector contacts by the use of thermography was developed. Two sets of measurements on disconnector contacts in the Swedish transmission

grid were carried out to establish the accuracy of the method. By utilising the results from the measurements estimates of the statistical distributions of the error sources were produced.

The results from the case studies show that the lack of detailed, high-quality data remains a critical problem when modelling reliability of power system equipment, even when using methods that require a minimum of data.

Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , xi, 42 p.
Series
Trita-ETS, ISSN 1650-674X ; 2005:05
Keyword [en]
Electrical power technology, Maintenance, reliability modelling, electrical power systems, ageing, failure mechanisms
Keyword [sv]
Elkraftteknik
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-273ISBN: 91-7178-054-8 (print)OAI: oai:DiVA.org:kth-273DiVA: diva2:8439
Presentation
2005-05-25, H1, Teknikringen 33, Stockholm, 09:30
Opponent
Supervisors
Note
QC 20101209Available from: 2005-06-07 Created: 2005-06-07 Last updated: 2010-12-09Bibliographically approved
List of papers
1. Reliability modelling of aged XLPE cables
Open this publication in new window or tab >>Reliability modelling of aged XLPE cables
2003 (English)In: Nordic Insulation Symposium (Nord-Is), 2003, 216-224 p.Conference paper, Published paper (Refereed)
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-8176 (URN)
Conference
The Nordic Insulation Symposium(Nord-Is), Tampere, Finland, June 2003
Note
QC 20100823Available from: 2008-04-03 Created: 2008-04-03 Last updated: 2010-12-09Bibliographically approved
2. A feasibility study for probabilistic modeling of aging in circuit breakers for maintenance optimization
Open this publication in new window or tab >>A feasibility study for probabilistic modeling of aging in circuit breakers for maintenance optimization
2004 (English)In: 2004 INTERNATIONAL CONFERENCE ON PROBABILISTIC METHODS APPLIED TO POWER SYSTEMS, NEW YORK: IEEE , 2004, 1020-1025 p.Conference paper, Published paper (Refereed)
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.

Place, publisher, year, edition, pages
NEW YORK: IEEE, 2004
Keyword
asset management, maintenance, aging, circuit-breakers reliability, reliability centered asset management (RCAM)
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-27200 (URN)000225735200173 ()2-s2.0-14544306110 (Scopus ID)
Conference
8th International Conference on Probabilistic Methods Applied to Power Systems Iowa State Univ, Ames, IA, SEP 12-16, 2004
Note

QC 20101209

Available from: 2010-12-09 Created: 2010-12-09 Last updated: 2017-06-08Bibliographically approved
3. A method for age modeling of power system components based on experiences from the design process with the purpose of maintenance optimization
Open this publication in new window or tab >>A method for age modeling of power system components based on experiences from the design process with the purpose of maintenance optimization
2005 (English)In: Proceedings. Annual Reliability and Maintainability Symposium, ISSN 0149-144X, 82-88 p.Article in journal (Refereed) Published
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.

Keyword
reliability modeling; maintenance; power system components
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-8177 (URN)10.1109/RAMS.2005.1408343 (DOI)000228469800015 ()2-s2.0-27744483092 (Scopus ID)
Note
QC 20100823Available from: 2008-04-03 Created: 2008-04-03 Last updated: 2010-12-09Bibliographically approved
4. Estimation of disconnector contact condition for modelling the effect of maintenance and ageing
Open this publication in new window or tab >>Estimation of disconnector contact condition for modelling the effect of maintenance and ageing
2005 (English)In: 2005 IEEE Russia Power Tech, PowerTech, 2005Conference paper, Published paper (Refereed)
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.

Keyword
Ageing; Contact condition; Disconnectors; Infrared image sensors; Maintenance; Reliability; Thermography
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-8178 (URN)10.1109/PTC.2005.4524406 (DOI)2-s2.0-51649085875 (Scopus ID)978-142441874-9 (ISBN)
Conference
2005 IEEE Russia Power Tech, PowerTech; St. Petersburg; 27 June 2005 through 30 June 2005
Note
QC 20100823Available from: 2008-04-03 Created: 2008-04-03 Last updated: 2010-12-09Bibliographically approved

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Citation style
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