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Power system performance when implementing dynamic rating on a wind farm connected transformer
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
2017 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

In this study, dynamic transformer rating (DTR) is applied on a medium power transformer thatis in use in the regional transmission grid. The transformer’s rated apparent power is 63 MVA, itis connected between a wind farm at 22kV and the grid, K¨orsb¨arsdalen, at 135kV. Power systemanalysis are carried out on the grid, with the objective to test how DTR and increased wind poweraffects the grid performance with respect to reliability, voltage stability and active losses.Historical measurements of ambient temperature and transformer loading is used to calculatefree transformer capacity based on unity life time loss. For the investigated transformer and giventime period the load can be increased without endanger transformer lifetime. The dynamicallyrated capacity exceeds the nominal capacity through the whole tested time period but DTR showsmost effective during winter when the ambient temperature is colder and therefore, has a coolingeffect on the transformer. DTR is used to calculate available transformer capacity but an increasedcapacity often comes with the expense of decreased lifetime and reliability. With the help of DTRthe current rate of transformer lifetime usage can be calculated and used as input to economicalanalysis where there is a trade of between reliability and profit from increased capacity.Through the power system analysis procedure presented in this report it is possible to sortout the faults that are most probable to cause severe violations, this information can be used forefficient reinforcement of the grid. The contingency and reliability analysis can work as base tofind the solutions that will decrease the probability for violations most efficiently. Furthermore,the developed procedure can also be used when expanding the grid and to determine which gridalternative that will be most reliable.

Abstract [sv]

I den h¨ar studien kommer en dynamisk modell f¨or en transformators maxkapacitet anv¨andas isyfte att utv¨ardera m¨ojligheterna f¨or utbyggnad av vindkraftsparken som ¨ar kopplad till transformatornsl°agsp¨anningssida. P°a transformatorns h¨ogsp¨anningssida finns regionn¨atet, K¨orsb¨arsdalen.Med hj¨alp av den dynamiska modellen ber¨aknas transformatorns varmaste punk. Dem varmastepunkten ¨ar bel¨agen p°a ¨ovre delen av transformatorns lindning. Det ¨ar denna punkts temperatursom s¨atter gr¨ansen f¨or hur mycket str¨om som kan s¨andas genom transformatorn utan att resultera io¨verhettning. O¨ verstiger den varmaste punkten en kritisk temperatur finns risk fo¨r att transformatornlivsl¨angd f¨orkortas. Konceptet dynamisk lastbarhet som bygger p°a termiska modeller kallasp°a engelska ,dynamic transformer rating (DTR).Vidare utv¨arderas effekterna av DTR p°a systemniv°a, K¨orsb¨arsdalens prestanda d°a DTR harimplementeras j¨amf¨ors med det ursprungliga n¨atets prestanda med avseende p°a tillf¨orlitlighet,sp¨anningsstabilitet och aktiva f¨orluster.Historiska m¨atv¨arden p°a omgivningstemperatur och transformatorns last anv¨ands f¨or att ber¨aknatransformatorns tillg¨angliga kapacitet, f¨or det studerade tidsspannet kan transformatorn anv¨andas¨over dess nominella effekt. P°a vintern d°a omgivningstemperaturen ¨ar l°ag kommer DTR till st¨orstnytta, den kalla luften har en kylande effekt p°a transformatorn vilket i sin tur betyder att en st¨orrestr¨om kan s¨andas genom transformatorns lindningar utan att en kritisk temperatur uppn°as.Genom det presenterade tillv¨agag°angss¨attet f¨or systemkraft analyser kan de fel som har st¨orstsannolikhet att resultera i allvarliga konsekvenser sorteras ut. Denna information kan anv¨andassom underlag f¨or reinvesteringar s°av¨al som vid expandering av det befintliga n¨atet.

Place, publisher, year, edition, pages
2017. , p. 59
Series
TRITA-EE, ISSN 1653-5146 ; 2017:139
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-215949OAI: oai:DiVA.org:kth-215949DiVA, id: diva2:1150174
External cooperation
Ellevio ABB
Educational program
Master of Science - Electric Power Engineering
Examiners
Available from: 2017-10-18 Created: 2017-10-18 Last updated: 2017-10-18Bibliographically approved

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