Change search
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
  • html
  • text
  • asciidoc
  • rtf
On reliability and maintenance modelling of ageing equipment in electric power systems
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Maintenance optimisation is essential to achieve cost-efficiency, availability and reliability of supply in electric power systems. The process of maintenance optimisation requires information about the costs of preventive and corrective maintenance, as well as the costs of failures borne by both electricity suppliers and customers. To calculate expected costs, information is needed about equipment reliability characteristics and the way in which maintenance affects equipment reliability. The aim of this Ph.D. work has been to develop equipment reliability models taking the effect of maintenance into account.

The research has focussed on the interrelated areas of condition estimation, reliability modelling and maintenance modelling, which have been investigated in a number of case studies. In the area of condition estimation two methods to quantitatively estimate the condition of disconnector contacts have been developed, which utilise results from infrared thermography inspections and contact resistance measurements. The accuracy of these methods were investigated in two case studies. Reliability models have been developed and implemented for SF6 circuit-breakers, disconnector contacts and XLPE cables in three separate case studies. These models were formulated using both empirical and physical modelling approaches. To improve confidence in such models a Bayesian statistical method incorporating information from the equipment design process was also developed. This method was illustrated in a case study of SF6 circuit-breaker operating rods. Methods for quantifying the effect of maintenance on equipment condition and reliability have been investigated in case studies on disconnector contacts and SF6 circuit-breakers. The input required by these methods are condition measurements and historical failure and maintenance data, respectively.

This research has demonstrated that the effect of maintenance on power system equipment may be quantified using available data. However, realising the full potential of these methods requires the gathering and utilisation of failure and maintenance data as well as condition measurements to be improved.

Place, publisher, year, edition, pages
Stockholm: KTH , 2008. , ix, 55 p.
Series
Trita-EE, ISSN 1653-5146 ; 2008:016
Keyword [en]
Reliability, maintenance, electric power systems, circuit breaker, disconnector, thermography
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-4688ISBN: 978-91-628-7465-0 (print)OAI: oai:DiVA.org:kth-4688DiVA: diva2:13436
Public defence
2008-04-25, F3, Lindstedtvägen 26, Stockholm, 13:15
Opponent
Supervisors
Note
QC 20100823Available from: 2008-04-03 Created: 2008-04-03 Last updated: 2010-08-23Bibliographically 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 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
3. 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
4. Hazard rate estimation for high-voltage contacts using infrared thermography
Open this publication in new window or tab >>Hazard rate estimation for high-voltage contacts using infrared thermography
2008 (English)In: Proceedings. Annual Reliability and Maintainability Symposium, ISSN 0149-144X, 233-239 p.Article in journal (Refereed) Published
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.

Keyword
disconnector, electrical contacts, hazard rate, maximum likelihood
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-8179 (URN)10.1109/RAMS.2008.4925800 (DOI)000272027800041 ()2-s2.0-67650286801 (Scopus ID)
Note
QC 20100823Available from: 2008-04-03 Created: 2008-04-03 Last updated: 2011-03-01Bibliographically approved
5. Circuit breaker failure data and reliability modelling
Open this publication in new window or tab >>Circuit breaker failure data and reliability modelling
2008 (English)In: IET Generation, Transmission and Distribution, ISSN 1751-8687, Vol. 2, no 6, 813-820 p.Article in journal (Refereed) Published
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.

Keyword
Capacitance; Circuit breaking arcs; Electric circuit breakers; Electric power transmission; Electric reactors; Power transmission; Reliability; Circuit breaker failures; Finnish; Hazard rates; Modelling; Shunt reactors; Transmission systems
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-8180 (URN)10.1049/iet-gtd:20080127 (DOI)000261469400004 ()2-s2.0-54949114772 (Scopus ID)
Note
QC 20100823. Uppdaterad från submitted till published (20100823).Available from: 2008-04-03 Created: 2008-04-03 Last updated: 2010-08-23Bibliographically approved
6. A practical method for benefit/cost analysis of preventive maintenance tasks in power system equipment
Open this publication in new window or tab >>A practical method for benefit/cost analysis of preventive maintenance tasks in power system equipment
2007 (English)In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 0885-8877Article in journal (Other academic) Submitted
Keyword
Circuit breakers, Cost effectiveness, Hazard rate, Maintenance modeling, Preventive maintenance, Reliability modeling, Virtual age
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-8181 (URN)
Note
QS 20120319Available from: 2008-04-03 Created: 2008-04-03 Last updated: 2012-03-19Bibliographically approved
7. Estimating the accuracy of thermography of disconnector contacts in the field
Open this publication in new window or tab >>Estimating the accuracy of thermography of disconnector contacts in the field
2008 (English)Report (Other academic)
Abstract [en]

This report summarises the results from an investigation into the accuracy of condition assessment of electrical contacts via thermography measurements in the field. The investigation was carried out in Ludvika, Sweden at the Swedish Transmission Research Institute (STRI) outdoor test site during the autumn of 2007. The investigation was performed as a part of the PhD project Modelling of power equipment reliability with special reference to the impact of maintenance carried out at the RCAM research group at the KTH School of Electrical Engineering.

Two naturally aged disconnector poles of the make ABB NSA 400/3150 was loaded up to their nominal load in three stages and the contact temperature rises were measured both using thermography and thermocouples attached to the contacts. The thermography measurements were carried out by am experienced technician from Vattenfall Service. After the first set of measurements some contacts were subjected to standard maintenance and the measurements were repeated.

The investigation resulted in statistical distribution for the errors related to the estimation of contact temperature rise at nominal load based on thermography measurements. These error distributions were used to simulate the accuracy of the estimations. Furthermore the investigation resulted in two linear regression models of the relationship between contact resistance and temperature rise as well as the effect of maintenance on contact temperature rise.

A conclusion from the measurements was that statistical models should be used to estimate the effect of maintenance on the contact condition as well as estimating the contact condition from resistance measurements.

Publisher
26 p.
Series
Trita-EE, ISSN 1653-5146 ; 2008:010
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-8182 (URN)
Note
QC 20100823Available from: 2008-04-03 Created: 2008-04-03 Last updated: 2010-08-23Bibliographically approved

Open Access in DiVA

fulltext(3006 kB)2141 downloads
File information
File name FULLTEXT01.pdfFile size 3006 kBChecksum MD5
d5138f0c3003c97ed7888eb78d6d98cfc06ce667e9cb5f3a82aad497936bbc99c4e7e7d3
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Lindquist, Tommie
By organisation
Electromagnetic Engineering
Other Electrical Engineering, Electronic Engineering, Information Engineering

Search outside of DiVA

GoogleGoogle Scholar
Total: 2141 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 2059 hits
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
  • html
  • text
  • asciidoc
  • rtf