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On Improvements of Power Transformer ConditionMonitoring by Considering Thermal Models
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. (Reliability Centered Asset Management (RCAM))ORCID iD: 0000-0002-5138-0272
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. (Reliability Centered Asset Management (RCAM))ORCID iD: 0000-0002-2964-7233
2012 (English)In: Proceedings of the 12th International Conference on Probabilistic Methods Applied to Power Sysmens, 2012Conference paper, Published paper (Refereed)
Abstract [en]

This paper aims to improve condition monitoring of power transformers by concerning thermal modeling. The common loss of life estimate could be used as a condition estimate during condition monitoring but for this estimate to be reliable, an accurate thermal model for the hotspot temperature calculations is absolutely essential to develop.

Studies have shown a significant deviation between measured and calculated hotspot values. This deviation is particularly pronounced during transient load at severe environments. Temperature modeling during transient load conditions puts high requirements on the dynamic part of the model; hence focus has been given to this particular load type in this paper. Moreover, the Nordic climate have winters with temperatures as low as -20C. In order to apply these models in these settings, this paper is discussing this as well. As possible thermal model improvements, this paper identifies the ambient temperature, loss variation with temperature, and oil viscosity changes with temperature as features which need to be utilized in the thermal model. This paper describes the current research within these areas.

Furthermore, presented in a concluding discussion, the appropriate approach for these models are seen to be either the thermal-electrical analogy or the soft modeling techniques.

Place, publisher, year, edition, pages
2012.
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-129981OAI: oai:DiVA.org:kth-129981DiVA: diva2:654003
Conference
PMAPS 2012 in Turkey
Note

QC 20131007

Available from: 2013-10-07 Created: 2013-10-07 Last updated: 2013-10-07Bibliographically 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

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Rosenlind, Johanna

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