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Reaktiv effekt i Dala Energis framtida mellanspänningsnät
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
2019 (Swedish)Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesisAlternative title
Reactive power in the future medium voltage grid of Dala Energi (English)
Abstract [en]

Dala Energi has large-scale plans for grid development and wants to have a better understanding of their current reactive power levels along with a future prognosis based on their plans. Changes in line inductance, shunt capacitance, area and placement put Dala Energi on the path to higher charging currents and higher reactive power generation.

In addition to causing concerns in their own grid, the increased reactive power generation can present challenges for the owner of the overlying grid. Transmission of reactive power upwards is not permitted in the current contract. Dala Energi’s grid is divided into 3 separate regions with a total of 19 larger substations, 12 of which are points of connection with the overlying grid. At times, 8 of the substations have transmitted reactive power upward and soon it will be all 12.

Region 1, where the 20-kV grid is located, is the biggest problem-area today, with upward-transmissions of 1 to 3 MVAr quite common and a considerable increase expected. Region 3 contains more than double the underground cable as the other two areas and might have had much greater side effects from the high shunt capacitance were it not for 3 industrial customers who consume a large portion of reactive power. In the coming years, however, Region 3 is expected to have capacitive reactive power levels nearly equal to those of Region 1. The combined reactive power baseline for all regions is expected to drop by 8.24 MVAr in the coming years.

The owner of the overlying grid controls Dala Energi’s 5 largest capacitor banks which have a rated capacity of 11.6 MVAr. With the entire capacity almost always connected, the upward transmission of reactive power becomes much greater. It would be very advisable to meet with the owner, discuss interaction between the two grids and examine the details of the current contract.

Compensation for excessive generation of reactive power is needed and is going to be essential in the future. The short-term variation of reactive power levels is so great that the use of fixed rating shunt reactors is ill-advised, especially under the current contract. Compensation with variable shunt reactors is recommended.

Place, publisher, year, edition, pages
2019. , p. 37
Keywords [sv]
Power grid, reactiv effect, Underground cable, Capacitor banks, shunt capacitance
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:umu:diva-160670OAI: oai:DiVA.org:umu-160670DiVA, id: diva2:1328249
External cooperation
Dala Energi
Subject / course
Elektronik
Educational program
Högskoleingenjörsprogrammet i Elkraftteknik - nätbaserat
Presentation
2019-06-04, Umeå University, MA121, Umeå, Sweden, 13:45 (Swedish)
Supervisors
Examiners
Available from: 2019-06-26 Created: 2019-06-20 Last updated: 2019-06-26Bibliographically approved

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