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Benefits of Reliability Centred Asset Management
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. (RCAM)ORCID iD: 0000-0002-2964-7233
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.ORCID iD: 0000-0001-6882-3642
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. (RCAM)ORCID iD: 0000-0002-5138-0272
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. (RCAM)ORCID iD: 0000-0003-4021-839X
Show others and affiliations
2013 (English)In: 22nd International Conference and Exhibition on Electricity Distribution (CIRED 2013), 2013, 0668- p.Conference paper, Published paper (Refereed)
Abstract [en]

This paper provides an overview of risk and reliability assessment techniques, some which are available for distribution system operators, and others that are in the process of development. The main contribution of this paper is showing the possibilities and benefits of detailed risk and reliability analysis. Six samples of findings from research developed over the last decade within the RCAM group (Reliability Centred Asset Management) at the Royal Institute of Technology, Stockholm Sweden, are presented. The research is directly associated with risk and asset management applied to power systems. The first three examples are within developed research, followed by three areas where great potential is seen: 1) The value of accurate thermal models of transformers; 2) The impact of tariff regulation on asset management decisions; 3) Detailed interruption studies; 4) Dynamic rating; 5) Combined risk and reliability analysis of primary equipment and control equipment; 6) Systematic diagnostic measures for asset management.

Place, publisher, year, edition, pages
2013. 0668- p.
Series
IET Conference Publications, Volume 2013, Issue 615
Keyword [en]
Diagnostic measures, Distribution systems, Management decisions, Primary equipments, Reliability assessments, Risk and reliability analysis, Royal Institute of Technology, Tariff regulation
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-123575DOI: 10.1049/cp.2013.0668Scopus ID: 2-s2.0-84897619482ISBN: 978-184919732-8 (print)OAI: oai:DiVA.org:kth-123575DiVA: diva2:627813
Conference
22nd International Conference and Exhibition on Electricity Distribution, CIRED 2013; Stockholm; Sweden; 10 June 2013 through 13 June 2013
Note

QC 20130718

Available from: 2013-06-12 Created: 2013-06-12 Last updated: 2015-10-02Bibliographically approved
In thesis
1. Lifetime modeling and management of transformers
Open this publication in new window or tab >>Lifetime modeling and management of transformers
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This work have studied and developed lifetime estimation methods for the power transformer and how these could be used for asset management purposes. It is researchperformed in the intersection of the fields of reliability theory, statistical analysis, and stochastic process theory applied to lifetime estimations and management of transformers.

The chosen approaches are the following. The thesis assess the effect of thermal stresses on the lifetime of the transformer. The effect of hotspot temperature is assessed with a loss of life measure. Within this study, improvements to the thermal model have been made.

The thesis moves on to an alternative method for lifetime estimation in which diagnostic measurements are forecasted using a stochastic process and iterative realizations of this stochastic process is used to estimate a probability distribution for the transformer.

The thesis moves on to study the loss of life measure from a system perspective by calculating the loss of life estimate from the load profiles of cold load pickup, increased electric vehicle penetration, and normal operation. These are applied in such a way that they can be used for asset management purposes.

Then, the thesis uses estimates of failure times with the aim to reach a probabilistic, dynamic capacity rating selection method which use a failure rate which is conditioned on the time-dependent load level.

Abstract [sv]

Det här arbetet har studerat och utvecklat metoder för estimering av transformatorlivslängden och hur dessa skulle kunna användas för hantering av tillgångar1. Detta är forskning framförd inom skärningspunkten mellan fälten: tillförlitlighetsteori, statistiskanalys och statistisk process teori. Detta har sedan blivit applicerat på hantering av transformatorer som tillgång.

En beskrivning av de valda ansatserna följer. Den här avandlingen skattar effekten av termisk påfrestning på livslängden av en transformator. Effekten av hotspot temperaturenestimeras med ett mått som skattar livslängdsförlusten för given drift. Inom den här studien så har förbättringar påden termiska modellen gjorts.

Avhandlingen går vidare till att utveckla en alternativ metod för livslängds estimering som nyttjar diagnostiska mätningar genom att prognosticera dessa med hjälp av en stokastisk process och genom iterativa realisationer av dessa, estimera sannolikhetsfördelningen för transformatorns livslängd.

Avhandlingen går vidare till att positionera livslängsförlustsmåttet i ett system genom att beräkna livslängdsförlusten under de olika driftförhållandena: kallastpåslag, ökad penetration av elektriska fordon, och normal drift. Dessa implementeras så att de kan användas med syftet att hantera tillgångar.

Slutligen så går avhandlingen vidare till att estimera feltider med syftet att välja en probabilistisk, dynamisk kapacitet som använder en felintensitet som är betingad på en tidsberoende belastningsnivå.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. xiii, 60 p.
Series
Trita-EE, ISSN 1653-5146 ; 2013:037
Keyword
transformers, lifetime modeling, asset management, thermal modeling, lifetime estimation
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-129971 (URN)978-91-7501-883-6 (ISBN)
Public defence
2013-10-21, F3, Lindstedtsvägen 26 (Entreplan), KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20131007

Available from: 2013-10-07 Created: 2013-10-07 Last updated: 2013-10-07Bibliographically approved
2. Condition measuring and lifetime modelling of electrical power transmission equipment
Open this publication in new window or tab >>Condition measuring and lifetime modelling of electrical power transmission equipment
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The electric grid is important in modern society, so the outages should be few. The transmission grid should have a real high availability, since it transports electrical energy across the country. Then, it is difficult to plan outages for maintenance and installation. This thesis lists twenty surveys about failures of circuit breakers and disconnectors, with data about the cause and the lifetime. It also contains a survey of about forty condition-measuring methods for circuit breakers and disconnectors, mostly applicable to the electric contacts and the mechanical parts.

As there is no published method to monitor the electric contacts at voltages around 400 kV, a system with IR sensors has been installed at the nine contacts of six disconnectors. The purpose is to avoid outages for maintenance by estimating the condition of the contacts while the disconnectors are still connected to high voltage. The measured temperatures are collected by radio and regressed against the square of the current, since the best exponent for the current was found to be 2.0. The coefficient of determination $R^2$ is high, greater than 0.9. This gives for each contact a regression coefficient, which can serve as an estimate of the condition of the contact. The higher the coefficient is, the more heat is produced at the contact, which can damage the material. This enables a ranking of the different contacts and shows which the worst ones are. This coefficient can also give a dynamic rating of the disconnector.

Abstract [sv]

Elnätet är viktigt i det moderna samhället, så antalet avbrott bör vara lågt. Särskilt stamnätet bör ha en särskilt hög tillgänglighet, då det transporterar elektrisk energi tvärsöver landet. Då blir det svårt att planera avbrott för underhåll och utbyggnad. Denna avhandling tar upp tjugo studier av fel i brytare och frånskiljare med data om felorsak och livslängd. Den har också en översikt av ett fyrtiotal olika metoder för tillståndsmätningar för brytare och frånskiljare, som huvudsakligen rör de elektriska kontakterna och de mekaniska delarna.

Eftersom det inte finns någon beskriven metod för att övervaka elektriska kontakter för spänningar på runt 400 kV, har ett system med IR sensorer installerats på de nio kontakterna på sex frånskiljare. Målet är att minska antalet avbrott för underhåll genom att skatta skicket hos kontakterna, när frånskiljarna fortfarande är kopplade till högspänning. De uppmätta temperaturerna tas emot genom radio och behandlas genom regression mot kvadraten av strömmen, då den bästa exponenten för strömmen visade sig vara 2,0. Förklaringsfaktorn $R^2$ är hög, över 0,9. För varje kontakt ger det en regressionskoefficient, som blir en skattning av kontaktens skick. Ju högre koefficienten är, desto mer värme utvecklas det i kontakten, vilket kan leda till skador på materialet. Kontakternas olika koefficienter ger en rankordning dem och därmed en möjlighet att prioritera vilken frånskiljare som ska underhållas först. Systemet kan också användas för att minska eller öka den tillåtna strömmen baserat på skicket.

Place, publisher, year, edition, pages
Stockhom: KTH Royal Institute of Technology, 2015. xii, 26 p.
Series
TRITA-EE, ISSN 1653-5146 ; 2015:026
Keyword
disconnectors, circuit breakers, reliability, lifetime, electric contacts, electric power transmission
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-167136 (URN)978-91-7595-611-4 (ISBN)
Presentation
2015-06-12, Seminarierum H21, Teknikringen 33, KTH, Stockholm, 10:15 (English)
Opponent
Supervisors
Funder
SweGRIDS - Swedish Centre for Smart Grids and Energy Storage
Note

QC 20150522

Available from: 2015-05-22 Created: 2015-05-21 Last updated: 2015-05-22Bibliographically approved
3. Reliability Evaluation of Distribution ArchitecturesConsidering Failure Modes and Correlated Events
Open this publication in new window or tab >>Reliability Evaluation of Distribution ArchitecturesConsidering Failure Modes and Correlated Events
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Power systems are in a phase of automation where intelligent components and sub-systems are employed to monitor, control and manage the grid. Quantifying the complex consequences on system reliability, from the integration of such automated and semi-automated equipment into the existing grid is important for maintenance optimisation and fault mitigation. This thesis identifies the  advanced approaches in power system reliability analysis with the potential to capture the complications and correlations in modern power grid after reviewing the traditional reliability evaluation methods.

A method for modelling the different modes of failures, possible in a substation and feeder architecture along with the probable false tripping scenarios was developed. An improved Reliability Block Diagram based approach was designed to count in the traditionally unaccounted failure cases affecting both the primary grid and the protectionand control equipment. The effect and corresponding trend of additional feeder lines in a radial distribution system on the net interruption rate experienced at load ends of feeders are derived and modelled. Such real-world substation architectures are analysed and the aforementioned trends are compared with those from the practical grid. Thus, the analysis was able to identify and measure the complex hidden failure probabilities due to both unwanted operation of breakers and functional failure of protection systems.

The measured probabilities were used to calculate the impact of protection and control equipment on system  reliability. The obtained results were verified by comparing it with the observations by energy researchers on ten years of protection system failure statistics. The application of the model and results, in optimal maintenance planning and power network optimisation are identified as the next step.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2015. xi, 38 p.
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-174178 (URN)
Presentation
2015-10-20, Q21, Osquldas väg 6B, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20151002

Available from: 2015-10-02 Created: 2015-10-01 Last updated: 2015-10-21Bibliographically approved

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Wallnerström, Carl JohanRosenlind, JohannaBabu, SajeeshWesterlund, Per

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