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Investigation of GIC effects on core losses in single phase power transformers
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
2011 (English)In: Archives of Electrical Engineering, ISSN 0004-0746, Vol. 60, no 1, 35-47 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents a method for estimation of core losses in banks of single phase power transformers that are subjected to an injected DC current such as geomagnetically induced currents (GIC). The main procedure of the core loss calculation is to obtain a magnetic flux density waveform in both time and location by using a novel algorithm based on 3D FEM inside the core and then to calculate the loss distribution based on loss separation theory. Also, a simple and effective method is proposed for estimation of losses of asymmetric minor loops by using combination of symmetric loops. The effect of DC biasing on core losses in single phase power transformers is investigated and the sensitivity of core type and material is evaluated. the results shows that DC current biasing could increase core losses up to 40 percent or even more.

Place, publisher, year, edition, pages
2011. Vol. 60, no 1, 35-47 p.
Keyword [en]
GIC, Power Transformers, Core losses
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-71045DOI: 10.2478/v10171-011-0004-9Scopus ID: 2-s2.0-79957508246OAI: oai:DiVA.org:kth-71045DiVA: diva2:486461
Note
QC 20120206Available from: 2012-01-30 Created: 2012-01-30 Last updated: 2012-11-21Bibliographically approved
In thesis
1. Electromagnetic Modelling of Power Transformers with DC Magnetization
Open this publication in new window or tab >>Electromagnetic Modelling of Power Transformers with DC Magnetization
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

DC currents that flow through the ground can be injected to the star windings of power transformers from their grounded neutral points and close their path with transmission lines. The geomagnetically induced currents (GICs) and AC/DC convertors of high voltage direct current (HVDC) systems are the sources of such DC currents. These currents may cause saturation of the core in power transformers that leads to destruction in the transformer performance. This phenomenon results in unwanted influences on power transformers and the power system. Very asymmetric magnetization current, increasing losses and creation of hot spots in the core, in the windings, and the metallic structural parts are adverse effects that occur in transformers. Also, increasing demand of reactive power and misoperation of protective relays menaces the power network. Damages in large power transformers and blackouts in networks have occurred due to this phenomenon

Hence, studies regarding this subject have taken the attention of researchers during the last decades. However, a gap of a comprehensive analysis still remains. Thus, the main aim of this project is to reach to a deep understanding of the phenomena and to come up with a solution for a decrease of the undesired effects of GIC.

Achieving this goal requires an improvement of the electromagnetic models of transformers which include a hysteresis model, numerical techniques, and transient analysis.

In this project until now, a new algorithm for digital measurement of the core materials is developed and implemented. It enhances the abilities of accurate measurements and an improved hysteresis model has been worked out. Also, a novel differential scalar hysteresis model is suggested that easily can be implemented in numerical methods. Three dimensional finite element models of various core types of power transformers are created to study the effect on them due to DC magnetization. In order to enhance the numerical tools for analysis of low frequency transients related to power transformers and the network, a distributed reluctance network method has been outlined. In this thesis a method for solving such a network problem with coupling to an electrical circuit and taking hysteresis into account is suggested.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. xv, 86 p.
Keyword
Transformer, Hysteresis, DC magnetization, GICs, FEM, reluctance network method
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-105395 (URN)978-91-7501-537-8 (ISBN)
Presentation
2012-11-29, Sal F3, Lindstedsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20121121

Available from: 2012-11-21 Created: 2012-11-20 Last updated: 2012-11-27Bibliographically approved

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