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Temperature and heat losses simulation in core and winding of a power transformer
Mälardalen University, Department of Public Technology. (Process Efficiency Improvement and Energy Management & Load Control)
2008 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [sv]

Simulering av temperatur och värmeförluster i kärna och lindning för en högspänningstransformator

“... Ett ljus som lyser dubbelt så starkt, varar hälften så länge …”, i analogi med ljuset så kan transformatorer köras med överlast inom vissa gränser, men med följden att livslängden blir kortare.

 

Transformatorn är vital del i en kraftindustri; transformatorn står för en betydande del av investeringen i en kraftanläggning. Tekniska livslängden för en transformator är cirka 30 år, men överlast kan förkorta livslängden. Överlast orsakar heta punkter i transformatorlindningen och kärnan och leder till nedbrytning av isoleringsförmåga samt orsakar förkortad livslängd och kylproblem. Det finns ett ökande intresse i att nyttja hela transformatorns kapacitet och samtidigt hålla sig inom säkra gränser. För att konstruera en transformator behövs kunskap om dynamik under varierande last, temperaturer i heta punkter, temperaturer i lindningen och förluster. Data kan erhållas genom att mäta på transformatorer, ställa upp och använda analytiska uttryck och utföra datorsimuleringar. Att bygga simuleringsmodell före fysisk prototyp har fördelen att man enkelt kan prova konsekvenserna av ändringar i transformatorns parametrar innan man bygger prototypen.

 

Under driften av transformatorn är temperaturen i den heta punkten den kritiska parametern. Temperaturen i heta punkten får inte överskrida en viss temperatur. Den sammanlagda effekten av åldring av isolering på grund av temperaturen i heta punkten bör också ligga lägre än ett förutbestämt värde.

Nya metoder behövs för detektion, övervakning och eliminering av heta punkter. I avhandlingen föreslås en ny apparatur och system för eliminering av heta punkter. Oljesprutningens effekt på transformatoroljan och oljecirkuleringen har utvärderats, simulerats och beräknats. Baserat på data och mätningar från en transformatorstation 230/63/20 kV i Sari i Iran har det utförts beräkningar och simuleringar. Resultaten visar att elektrisk nyttig energi kan ökas genom att minska begränsningarna i last på grund av problem med heta punkter i transformatorer. System för sprutning av olja är undersökta och modifierade för lokal kylning. En robust algoritm har föreslagits, utvecklats och optimerats för ökad noggrannhet i kylningen. Ett viktigt resultat är möjligheten att simulera temperaturer, speciellt heta punkter och förluster i magnetiska kärnan och lindningarna.

Abstract [en]

“…A candle that burns twice as bright lasts half as long …” So too transformers can run at over rated loadings within limits, consequently shortening their expected service life.

 

Power transformers are vital devices in power industries. Electrical utilities have to pay a significant portion of capital investment costs for Power transformers. Although the useful service life of transformer is around of 30 years, but some times utility needs to achieve over loading of transformers. It can decrease transformer expected life. Over loading and other problems make a hottest spot point in windings and core and as a result, these lead to insulation degradations, loss of life and cooling problems. There fore, here is an increased interest in safely utilizing all available capacity.

In order to design a power transformer it is essential to understand its performance in loading times, same as hottest spot temperature, temperature profile in windings and losses. Exactly these can be obtained by measurements on physical transformers, analytical expressions and computer simulations. One important benefit on using of simulations before prototype is that the transformer can be modelled and simulated before it is built physically and that the consequences of varying dimensions and parameters easily can be tested.

 

During the operation of power transformers, the critical parameter is the hottest temperature. The hot spot temperature (HST) has to be held under a prescribed limit. A cumulative effect of insulation aging, depending on time change of hot spot temperature, should be less than a planed value.

Therefore, essentially utilities need to find a new method for hot spot detecting, monitoring and removing. In this thesis, I have suggested a new apparatus and system for hot spot point removing. The effects of oil spraying has been assessed, simulated and calculated. Using test data of 230/63/20kV Sari substation, simulation and calculation (using this device) have been performed; consequently it has been shown that electrical utility can mitigate the limitations of loading due to HST problem in transformers. Oil spraying system are investigated and modified to apply for local cooling. A robust algorithm have been proposed and trained for working out this task and are further optimally combined to give an improved accuracy.

One important result of the thesis is the possibility to simulate temperature including the hot spot temperature and losses in the magnetic core material and windings.

 

Place, publisher, year, edition, pages
Västerås: Mälardalen University , 2008.
Series
Mälardalen University Press Licentiate Theses, ISSN 1651-9256 ; 86
Keywords [en]
Electric Power Transformer, Losses, Simulation, Temperature, Calculation
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electronics
Identifiers
URN: urn:nbn:se:mdh:diva-1503ISBN: 978-91-85485-83-3 (print)OAI: oai:DiVA.org:mdh-1503DiVA, id: diva2:113721
Presentation
Lambda, MDH, Västerås, Sweden (English)
Opponent
Supervisors
Projects
Electric Power TransformerAvailable from: 2008-10-27 Created: 2008-10-24 Last updated: 2010-06-04Bibliographically approved
List of papers
1. A novel device (oil spraying system) for local cooling of hot spot and high temperature areas in power transformer
Open this publication in new window or tab >>A novel device (oil spraying system) for local cooling of hot spot and high temperature areas in power transformer
2007 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Power transformer is a vital device in substations. Load and no load losses create a hot spot point in transformer, so it is obviously necessary to limit the core temperature to values that cause no damage to the core itself, adjacent materials, or the oil. Core temperatures as low as 110 C–120 may degrade oil. This has led experts in the field to suggest that 130 C would be a reasonable limit for the core temperature. For this reason, need to a device for local cooling is necessary. Authors in this paper find a novel method for oil cooling in hot spot point or area. Oil spraying device is simulated and then path of pressured oil after shooting in hot spot point, is evaluated. With using of 230/63/20kv Punel substation in Iran data, and after simulation and calculation, authors find that with using of this device utilities could remove their problem for over loading of transformers in the load peak time.

Place, publisher, year, edition, pages
Västerås, Sweden: IGECIII, 2007
National Category
Energy Engineering
Identifiers
urn:nbn:se:mdh:diva-1240 (URN)978-91-85485-52-9 (ISBN)
Conference
3rd INTERNATIONAL GREEN ENERGY CONFERENCE, 17-21 june 2OO7, VÄSTERÅS, SWEDEN
Available from: 2008-10-10 Created: 2008-10-10 Last updated: 2016-01-18Bibliographically approved
2. Identification of a best thermal formula and model for oil and winding
Open this publication in new window or tab >>Identification of a best thermal formula and model for oil and winding
2007 (English)Conference paper, Published paper (Refereed)
Abstract [en]

System identification is about building models from data. A data set is characterized by several pieces of information: The input and output signals, the sampling interval, the variable names and units, etc.Similarly, the estimated models contain information of different kinds, estimated parameters, their covariance matrices, and model structure and so on. In this paper we collected Temperature of oil and winding in 230/63kv transformer of SARI Substation and considered the winding temperature for input in the model and oil temperature for out put. After that calculated their data by MATLAB software and get a new model with the good best fit for the heat transfer from core and winding to oil. For verification of were calculated results, has been simulated the process in COMSOL Software.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2007
Series
Linköping Electronic Conference Proceedings, ISSN 1650-3686
Keywords
best fit, simulation, identification, error, model
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:mdh:diva-1247 (URN)
Conference
The 48th Scandinavian Conference on Simulation and Modeling (SIMS 2007); 30-31 October; 2007; Göteborg (Särö)
Available from: 2008-10-10 Created: 2008-10-10 Last updated: 2016-01-18Bibliographically approved
3. A new apparatus for mitigating the hot spot problem in large power transformers using Ants algorithm
Open this publication in new window or tab >>A new apparatus for mitigating the hot spot problem in large power transformers using Ants algorithm
2007 (English)In: IEEE PES PowerAfrica 2007 Conference and Exposition, PowerAfrica, 2007, p. 587-594Conference paper, Published paper (Refereed)
Abstract [en]

Hot spot temperature (HST) is the most important parameter in the operation of power transformers. The HST has to be held under a prescribed limit. HST has a considerable effect on the insulation aging. Therefore detecting, monitoring and removing the HST could be a very important and necessary action for Utilities. A new design of oil spraying and its effect, along with a thermal management in a transformer cooling system has been studied in this paper. The effect of oil fluid flow on the HST problem has been considered in this paper; and the calculations and simulation have been performed by Ants algorithm. The simulation results have been validated based on a 230/63/20 kV, 250MVA transformer at the Sari substation in Iran, and the results indicate that the new design could mitigate the limitations of transformer loading due to the HST problem. The Ants algorithm have been proposed and applied for accomplishing this task and to give an improved level of accuracy.

Keywords
Ant algorithm, simulation, nozzle, oil spraying, oil
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:mdh:diva-1237 (URN)10.1109/PESAFR.2007.4498064 (DOI)000257092200095 ()2-s2.0-50649120118 (Scopus ID)1-4244-1478-4 (ISBN)
Conference
IEEE PES PowerAfrica 2007 Conference and Exposition, PowerAfrica; Johannesburg; South Africa; 16 July 2007 through 20 July 2007
Available from: 2008-10-10 Created: 2008-10-10 Last updated: 2019-06-26Bibliographically approved
4. Thermal evaluation and energy saving with loss reduction in core and winding of power transformers
Open this publication in new window or tab >>Thermal evaluation and energy saving with loss reduction in core and winding of power transformers
2007 (English)Conference paper, Published paper (Refereed)
Abstract [en]

A power loss, heat generation and heat distribution evaluations in a large-scale oil cooled power transformer are presented here, along with the details of computer implementation and experimental verification. In this paper, we consider that core power losses are approximately constant with temperature various or might decreased with that. Winding temperature and oil will increase with the load increasing and might create a hot spot and that is caused by degradation insulation and the loss of life in the power transformer. Therefore the authors tried to Asses these phenomena with use of electrical and thermal soft wares. On the results (with Iranian network data) of simulation showed that in case of oil spraying on the hotspot point or area, very low temperature with the best conditions would be obtained. Then it is best to provide a cooling system with the best insulation and with the minimum side effect on the magnetic and electrical field distribution. Finally by reduction in transformer losses, could savings potential of 22 TWh / year for EU.

Keywords
hysteresis loss, eddy current loss, ONAN, Oil spraying system, nozzles, Energy
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-1257 (URN)978-91-84585-52-9 (ISBN)
Conference
IGECIII, Västerås, Sweden, June 17-21, 2007
Available from: 2008-10-10 Created: 2008-10-10 Last updated: 2015-10-12Bibliographically approved
5. Thermal and hot spot evaluations on oil immersed power Transformers by FEMLAB and MATLAB software’s
Open this publication in new window or tab >>Thermal and hot spot evaluations on oil immersed power Transformers by FEMLAB and MATLAB software’s
2007 (English)In: EuroSime 2007: International Conference on Thermal, Mechanical and Multi-Physics Simulation Experiments in Microelectronics and Micro-Systems, 2007, 2007, p. 529-534Conference paper, Published paper (Refereed)
Abstract [en]

Transformers are important and expensive elements of a power system. Inordinate localized temperature rise, hottest spot temperature (HST), causes rapid thermal degradation of insulation and subsequent thermal breakdown. To prescribe the limits of short-term and long-term loading capability of a transformer, it is necessary to estimate the HST of transformer winding to as high a degree of accuracy as can possibly be made. These papers have now improved the accuracy of estimation of hottest spot temperature. Inordinate temperature rise in a power transformer due to load current is known to be the most important factor in causing rapid degradation of its insulation and decides the optimum load catering ability or the load ability of a transformer. The Top Oil Temperature (TOT) and Hottest Spot Temperature (HST) being natural outcome of this process, an accurate estimation of these parameters is of particular importance. IEEE / IEC among others have proposed procedure to estimate the temperatures, however, the accuracy of the predictions are not always as good as are desired. Unacceptable temperature rise may occur due to several fault conditions other than overloading, and hence warrant an online monitoring of the transformer.

Keywords
power transformer, HST, TOT, Oil, Temperature, Henkel transform
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-1252 (URN)10.1109/ESIME.2007.359924 (DOI)000246444700083 ()2-s2.0-36349021992 (Scopus ID)9781424411061 (ISBN)
Conference
EuroSime 2007: International Conference on Thermal, Mechanical and Multi-Physics Simulation Experiments in Microelectronics and Micro-Systems, 2007; London; United Kingdom; 16 April 2007 through 18 April 2007
Available from: 2008-10-10 Created: 2008-10-10 Last updated: 2018-08-21Bibliographically approved

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CiteExportLink to record
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Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
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Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
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  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf