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Reliability considerations and economic benefits of dynamic transformer rating for wind energy integration
KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering. (QED Asset Management group)ORCID iD: 0000-0002-4065-715X
ABB AB Corporate Research.
KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering. (QED Asset Management group)ORCID iD: 0000-0002-2964-7233
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2019 (English)In: International Journal of Electrical Power & Energy Systems, ISSN 0142-0615, E-ISSN 1879-3517, Vol. 106, p. 598-606Article in journal (Refereed) Published
Abstract [en]

An increasing share of renewable energy on the electricity market creates the need for economic and efficient production, operation and integration technologies, associated with the specific behavior of renewable energy sources (RES). Dynamic rating (DR) provides a possibility to apply improvements to the system both during planning and operation stages. The DR benefits are well described in various literature sources. However, DR is often focused on more efficient exploitation of power lines, not power transformers. Power transformers are costly equipment and their efficient usage and planning can have drastic effect on total costs.

Our analysis focuses on the dynamic transformer rating (DTR) for wind energy applications. The main objective is to study reliability effects of DTR from the component perspective. We utilize existing knowledge about transformer heat balance models from IEC and IEEE standards to obtain information on the loss of life (LOL) of the transformer under investigation and propose possible improvements for the system in question. The method can be employed for identifying the appropriate transformer size by taking into account ambient temperature and load variations and then overloading the transformer beyond nameplate ratings. The reliability of the proposed application is ensured by calculating the risk of overloading the transformer for each day of the year. A risk of overloading is quantified as LOL of the transformer. The risk is presented as a function of ambient temperature and duration of an overload. The final step consists of an economic analysis, which demonstrates economic benefits of DTR application.

Place, publisher, year, edition, pages
2019. Vol. 106, p. 598-606
Keywords [en]
Dynamic transformer rating, Loss of life, Heat balance, Wind energy
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-239531DOI: 10.1016/j.ijepes.2018.09.038ISI: 000454377000055Scopus ID: 2-s2.0-85056630521OAI: oai:DiVA.org:kth-239531DiVA, id: diva2:1265520
Projects
Dynamic rating with applications to renewable energy
Funder
SweGRIDS - Swedish Centre for Smart Grids and Energy Storage, FPS18Swedish Energy AgencyStandUp for Wind
Note

QC 20181130

Available from: 2018-11-23 Created: 2018-11-23 Last updated: 2020-01-09Bibliographically approved
In thesis
1. Dynamic Rating with Applications to Renewable Energy
Open this publication in new window or tab >>Dynamic Rating with Applications to Renewable Energy
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Dynamic rating (DR) of power components is a method for assessing real-time capacity of large scale power transmission and distribution devices (commonly: transmission lines, power transformers, underground cables) and using this knowledge for adjusting loading limits of these components. 

Dynamic rating of power lines or dynamic line rating (DLR) is a pioneering technology in the area of dynamic rating. Heat balance of an overhead conductor is a defining factor when designing capacity limits for power lines. The maximum ampacity of the power line depends on the factors, such as ambient temperature, wind speed, wind direction, solar radiation, humidity, location, height above the sea level and conductor dimensions and material properties. 

Dynamic transformer rating (DTR) is a new emerging technology with high interest from industry and academia. Similarly to DLR, the dynamic rating of transformers relies on a thermal assessment of the device by locating the hottest spot in the transformer windings. The hot-spot temperature is the limiting factor for determining the maximum allowable ampacity. By shifting from the power-constrained the loading limits to the temperature-constrained, it is possible to achieve much better utilization of power transformer.

Recently, DLR became a recognizable concept in the power systems research community; DTR is also slowly gaining its popularity among researchers. At the same time, the industry begins to recognize DR benefits and invest in dynamic rating technologies. However, there exist many unanswered questions to the technology's reliability, applicability and safe operation. One of the central questions is: how to integrate dynamic rating into short term and long term planning decisions?

he results of the work presented in this thesis show that dynamic rating has high potential to improve power system performance and reduce the costs for power dispatch and increase the share of the renewable energy in the electricity mix. Together with that dynamic rating can help to make renewable energy more accessible by decrease the investment needed for supplying the electricity demand and providing cheaper and faster grid connection.

Abstract [sv]

Dynamisk rating (DR) av elkraftkomponenter syftar till tekniker för att uppskatta kapaciteten hos komponenter för storskalig överföring av elkraft (vanligtvis: kraftledningar, transformatorer, underjordiska kablar) i realtid och använda denna information för att justera belastningsgränserna för dessa. 

Dynamisk rating av kraftledningar (DLR) är en nydanande teknik inom detta område. Värmebalansen för en kraftledning är en viktig faktor för att bestämma dess överföringskapacitet. En kraftlednings maximala strömledningsförmåga beror därför på faktorer så som temperatur, vindhastighet, vindriktning, solstrålning, fuktighet, geografiskt läge, höjd över havet och ledarens dimensioner och materialegenskaper.

Dynamisk rating av transformatorer (DTR) är en ny teknik med stort intresse från industri och akademi. Liknande som för DLR använder sig DTR av en uppskattning av den hot-spot temperaturen, hos komponenten genom att hitta den varmaste punkten i transformatorlindningarna. Hot-spot temperaturen är den begränsande faktorn för att avgöra transformatorns överföringskapacitet. Genom att låta den maximalt tillåtna belastningen bero på temperaturen istället för effekten kan utnyttjandet av transformatorn förbättras väsentligt. 

Nyligen har DLR blivit ett erkänt koncept inom forskningen för elkraft och DTR har också börjat bli populärt bland forskare. Samtidigt har industrin börjat se fördelarna av DR och investera i dessa tekniker. Det finns dock fortfarande många frågor kring teknikern som rör tillförlitlighet, applicerbarhet och säkerhet. En av de viktigaste frågorna är hur man bäst kan integrera dynamisk rating i kort- och långtidsplaneringen av elkraftsystem.

Resultaten av arbetet som presenteras i denna avhandling visar att dynamisk rating har en stor potential att minska kostnaderna för driften av elnätet och tillåta integrering av mer förnybara energikällor. Dessutom kan dynamisk rating göra förnybar energi mer tillgänglig genom att minska de investeringar som krävs för att tillgodose efterfrågan på elektricitet och möjliggöra snabbare och billigare anslutning till elnätet.

Place, publisher, year, edition, pages
Stockholm,: KTH Royal Institute of Technology, 2020. p. 84
Series
TRITA-EECS-AVL ; 2020:3
Keywords
dynamic rating, dynamic line rating, dynamic transformer rating, power transformers, power system optimization, wind farm planning
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-266363 (URN)978-91-7873-390-3 (ISBN)
Public defence
2020-01-31, Kollegiesalen, Brinellvägen 8, Stockholm, 14:00 (English)
Opponent
Supervisors
Funder
Swedish Energy AgencySweGRIDS - Swedish Centre for Smart Grids and Energy Storage, FPS18StandUp for Wind
Note

QC 20200109

Available from: 2020-01-09 Created: 2020-01-09 Last updated: 2020-01-21Bibliographically approved

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