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Influence of Ambient Temperature on Transformer Overloading During Cold Load Pickup
KTH, School of Electrical Engineering (EES), Electric Power Systems.
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.ORCID iD: 0000-0002-5138-0272
KTH, School of Electrical Engineering (EES), Electric Power Systems.
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
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2013 (English)In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 0885-8877, Vol. 28, no 1, 153-161 p.Article in journal (Refereed) Published
Abstract [en]

This paper proposes a method to investigate the socioeconomical aspects of transformer overloading during a cold load pickup (CLPU) in residential areas. The method uses customer damage functions to estimate the cost for their power interruption and a deterioration model to estimate the cost for transformer wear due to the CLPU. A thermodynamic model is implemented to estimate the peak and the duration of cold residential load. A stochastic differential equation is used to capture the volatility of the load and to estimate the probability for transformer overloading. In a numerical example, an optimal cold load pickup for a two-area system is demonstrated where transformer overloading is allowed. In this example, an ambient temperature threshold is identified, where transformer overloading is socioeconomically beneficial.

Place, publisher, year, edition, pages
2013. Vol. 28, no 1, 153-161 p.
Keyword [en]
Cold load pickup (CLPU), restoration, transformer aging, transformer loading
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
URN: urn:nbn:se:kth:diva-117646DOI: 10.1109/TPWRD.2012.2219079ISI: 000312889500018ScopusID: 2-s2.0-84871718818OAI: diva2:602778

QC 20150625

Available from: 2013-02-04 Created: 2013-02-01 Last updated: 2015-06-25Bibliographically 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.
Trita-EE, ISSN 1653-5146 ; 2013:037
transformers, lifetime modeling, asset management, thermal modeling, lifetime estimation
National Category
Engineering and Technology
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)

QC 20131007

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

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