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A novel device (oil spraying system) for local cooling of hot spot and high temperature areas in power transformer
Mälardalen University, School of Sustainable Development of Society and Technology. (Process Efficiency Improvement+Energy Management & Load Control)
(Process Efficiency Improvement+Energy Management & Load Control)
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: urn:nbn:se:mdh:diva-1240ISBN: 978-91-85485-52-9 (print)OAI: oai:DiVA.org:mdh-1240DiVA, id: diva2:37703
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
In thesis
1. Temperature and heat losses simulation in core and winding of a power transformer
Open this publication in new window or tab >>Temperature and heat losses simulation in core and winding of a power transformer
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
Electric Power Transformer, Losses, Simulation, Temperature, Calculation
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electronics
Identifiers
urn:nbn:se:mdh:diva-1503 (URN)978-91-85485-83-3 (ISBN)
Presentation
Lambda, MDH, Västerås, Sweden (English)
Opponent
Supervisors
Projects
Electric Power Transformer
Available from: 2008-10-27 Created: 2008-10-24 Last updated: 2010-06-04Bibliographically approved

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