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Impact of transformer core size on the reactive power requirement of power transformers due to GIC
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
2014 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesisAlternative title
Inverkan av magnetkärnans storlek på det reaktiva effektbehovet hos krafttransformationer på grund av GIC (Swedish)
Abstract [en]

Geomagnetically induced currents (GIC) are a natural phenomenon which arises due to solar

storms. During a solar storm, large amounts of magnetized plasma are ejected from the surface

of the sun. When this plasma reaches earth, it causes fluctuations in the geomagnetic field. Such

 fluctuations may induce DC over-currents in long transmission lines. These currents affect the

transmission system several dierent ways; In particular high voltage transformers are sensitive to

GIC. When the over-current flows through the transformer windings the reactive power absorption

of the transformer increases, which may lead to voltage instability in the power system. For this

project, the main issue has been to determine whether or not an increase in the size of the transformer

core leads to the reactive power absorption being less sensitive to GIC. In order to investigate

this issue a recently developed transformer model has been used; the Hybrid transformer model.

This model combines the principle of duality with a matrix representation of the transformer. The

Hybrid transformer model, which has recently been implemented in the power system simulations

software PSCAD, has been used to simulate GIC events in transformers of varying core sizes. The

results from these simulations indicate that a larger transformer core is associated with a smaller

increase in reactive power absorption during a GIC event. It is also clear that the reactive power

absorption as a function of GIC magnitude is a non-linear function when the Hybrid transformer

model is applied. This function has previously been considered a linear function.

Abstract [sv]

Geomagnetiskt inducerade strömmar (GIC) är ett naturfenomen som uppstår till följd av solstormar.

Vid en solstorm kastas stora mängder magnetiserad plasma ut från solens yta, och när denna

plasma når jorden uppstår  uktuationer i det jordmagnetiska fältet. Detta kan leda till att DCstr

ömmar induceras i långa transmissionsledsningar. Dessa överströmmar påverkar kraftsystemet

på  era olika sätt, bland annat har de en stor påverkan på transformatorer. Då överströmmen

 yter genom transformatorlindningarna ökar det reaktiva eektuttaget för transformatorn, vilket

kan leda till spänningsinstabilitet i systemet. En fråga som legat till grund för detta projekt är huruvida

en ökning av transformatorkärnans storlek gör transformatorns reaktiva eektuttag mindre

känsligt för GIC. För att undersöka detta har en ny transformatormodell använts; den såkallade

hybridmodellen som kombinerar dualitetsprincipen med en matrisrepresentation av transformatorn.

Denna modell, som nyligen implementerats i simuleringsprogrammet PSCAD, har använts för att

simulera GIC i transformatorer med kärnor av olika storlekar. Resultaten från dessa simuleringar

indikerar att större transformatorkärna medför mindre förändring av det reaktiva eektuttaget när

transformatorn utsätts för GIC. Det är även tydligt att det reaktiva eektuttaget som funktion av

GIC är en icke-linjär funktion när hybridmodellen används. Denna funktion har tidigare ansetts

vara linjär.

Place, publisher, year, edition, pages
2014. , 36 p.
Series
EES Examensarbete / Master Thesis, TRITA XR-EE-ETK 2014:16
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-157347OAI: oai:DiVA.org:kth-157347DiVA: diva2:769799
External cooperation
Statnet
Educational program
Master of Science in Engineering - Electrical Engineering; Master of Science - Electric Power Engineering
Examiners
Available from: 2014-12-09 Created: 2014-12-09 Last updated: 2014-12-09Bibliographically approved

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