Analysis of High-Frequency Electrical Transients in Offshore Wind Parks
Doktorsavhandling, 2011

In this thesis, a study of high frequency electromagnetic transient phenomena is performed. Models of various components needed for simulations of high frequency transients, such as for transformers, cables and breakers are developed. Measurements were performed in Chalmers research laboratory as well as at ABB Corporate Research in Västerås, Sweden for the purpose of parameter estimation of models and for verification of simulations. Critical cases where the voltage surges of the magnitude and/or rise time above basic lightning impulse voltage level appear, are identified. Also, some transient protection schemes are analyzed and the performance of different transient mitigation devices is studied. Furthermore, the voltage distribution along the winding during very fast transients is studied in order to estimate turn-to-turn voltages and the critical voltage envelope. In the work it was found that simulations of the high frequency transients are in a very good agreement with the measurements obtained in the laboratory. Simulations predicted accurately critical surges with the highest magnitude and matched with good accuracy surge waveforms recorded during the measurements. The accuracy of the rise times is within 10%, while the magnitudes during the critical cases are within a 5% margin. During the testing and simulations, surges which exceed the basic lightning impulse voltage level of dry-type transformers specified by IEEE standards, both in magnitude and rise time are observed at the transformers even when surge arresters are used to protect the transformers. Furthermore, obtained voltage surges exceeded the proposed critical voltage envelope. It is shown that the most critical voltage strikes are obtained with dry-type transformers, where the rise time is five to ten times shorter compared to oil-insulated transformer with the same rating. It was confirmed both in simulations and measurements that the use of additional transient protections devices such as surge capacitors and RC protections, decreased the magnitude of surges to be below the critical level. The analysis of the voltage during very fast transients showed that the rise time of the transients directly influences the magnitude of the turn-to-turn voltages. Furthermore, during the breaker closing transient, turn-to-turn voltages, measured in delta connected dry-type transformers, were 2.5 times higher than the voltages obtained during the same transient with a wye connected dry-type transformer, or during the stress with a 4.4 p.u. lightning impulse voltage.

transient overvoltage

restrikes

very fast transient

voltage escalation

prestrikes

surge protection

surge

breaker

room EA, Hörsalsvägen 11, Chalmers University of Technlology, 412 96 Göteborg
Opponent: Bjørn Gustavsen

Författare

Tarik Abdulahovic

Chalmers, Energi och miljö, Elkraftteknik

Combining MV laboratory and simulation resources to investigate Fast Transient Phenomena in Wind Cable Systems

European Offshore Wind 2009, Stockholm,; (2009)

Konferensbidrag (offentliggjort, men ej förlagsutgivet)

An experimental investigation of switching transients in a wind collection grid scale model in a cable system laboratory

CIRED, 20th International Conference on Electricity Distribution,; (2009)p. 1-4

Konferensbidrag (offentliggjort, men ej förlagsutgivet)

Comparison of switching surges and basic lightning impulse surges at transformer in MV cable grids

Nordic Wind Power Conference, Bornholm, Danmark,; (2009)

Konferensbidrag (offentliggjort, men ej förlagsutgivet)

Simulation accuracy of the built-in PSCAD and an owner-defined synchronous machine model

COMPEL - The International Journal for Computation and Mathematics in Electrical and Electronic Engineering,; Vol. 29(2010)p. 840-855

Artikel i vetenskaplig tidskrift

Styrkeområden

Energi

Ämneskategorier

Annan elektroteknik och elektronik

ISBN

978-91-7385-598-3

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 3279

room EA, Hörsalsvägen 11, Chalmers University of Technlology, 412 96 Göteborg

Opponent: Bjørn Gustavsen