Electrical Insulation and Dielectrics in Repetitive Pulsed Power
Dielectrics are the fundamental building blocks of electrical insulation for centuries. Many components in power systems must be electrically insulated for proper functionality. Although dielectric materials have been studied in every aspect of science and technology from chemistry, physics, utility power, and advance electric power systems, as the systems became large and complicated, higher electrical stresses are imposed onto dielectrics and insulation. Continuous partial discharge or corona activities are a serious problem usually associated with insulation degradation, electromagnetic interference (EMI), and the upset of poorly protected sensitive circuits without proper shielding. For example, in space/aerospace context the influence of factors such as reduced ambient pressures, outgassing, existence of ionosphere and space plasma must also be considered, along with high frequency and localized high field stresses on insulation. This presentation is an overview of dielectric material fundamentals, including the high voltage electrical insulation of space power and high voltage pulsed systems over the years. The studies of pertinent high voltage effects on insulation including theory, technology development, and applications that encompasses phenomena such as high electric field stress, high magnetic flux, and high frequency issues relating to the performance of all insulation media are also presented.
Gaseous Breakdown at High Frequencies
In general, power devices and systems operating in vacuum or sub-atmospheric pressures are more susceptible to partial discharges, corona, or volume discharges due to the partial vacuum conditions. In space power systems, for example, these activities are usually are great concerns and require major design considerations. Currently space power systems operate voltages higher than the traditional 28 V. With the availability of high power electronic devices operating at higher switching frequencies, these power systems also operate under frequencies and waveforms quite different from those studied and developed for earthbound power distribution systems. Thus, these advancements make the corona and partial discharge problems more important than before. This presentation is an overview of systems and components subject non-uniform, high frequency and high fields operated in sub-atmospheric pressures and associated high frequency gaseous breakdown. Also reviewed are the breakdown characteristics of gases, such as helium, nitrogen and air, under unipolar repetitively pulsed voltage at frequencies varying from 10 kHz to 240 kHz in partial vacuum. Comparison with dc and unipolar kHz frequency sinusoidal fields is also discussed. Breakdown voltage as a function of pressure in the range where “Pashce” minimum occurs, along with optical emission characteristics of plasma at breakdown are presented.
Hulya Kirkici is Professor and the Department Chair of Electrical and Computer Engineering at the University of South Alabama. She received the B.S. and M.S. in physics from Middle East Technical University (METU), Ankara, Turkey; and the Ph.D. in electrical engineering from Polytechnic University (currently NYU – Poly), Brooklyn, NY. Previously, Dr. Kirkici was Professor of electrical and computer engineering at Auburn University (1992-2016), visiting scholar / consultant and Summer Faculty Fellow at the Air Force Research Laboratory – Wright Patterson Air Force
Base, (2014-2015), and visiting scientist/engineer at NASA, Marshall Space Flight Center, Huntsville, AL (1999-2000).
Dr. Kirkici is a Fellow of IEEE (Institute of Electrical and Electronics Engineering) for “contributions to high frequency, high field dielectric breakdown and electrical insulation for space and aerospace power systems” (class of 2017), a recipient of the IEEE Eric O. Forster Distinguished Service Award, the highest service honor given by the Dielectrics and Electrical Insulation Society (2015), IEEE William G. Dunbar Award “for continuing contribution to high-voltage and high frequency insulation research and engineering education,” (2014) and a recipient of the IEEE Sol Schneider Award “for continuing technical and administrative leadership in the power modulator and high voltage communities,” (2010).
Dr. Kirkici’s research interests are in electrical insulation and high-frequency dielectric breakdown in space and aerospace environments, cold plasmas, repetitive pulsed power, and high voltage engineering. She has published over 100 peer-reviewed journal and conference articles and given plenary and invited talks in these related topics over the years nationally and internationally (in USA, Turkey, Japan, South Korea, and China). Dr. Kirkici is members of IEEE, American Physical Society (APS), Sigma Xi Scientific Honor Society, Eta Kappa Nu Electrical Engineering Honor Society, and American Association of University Women (AAUW).
Dr. Kirkici serves on the IEEE Periodical Review Committee (2016 – present) and IEEE Access Editorial Board (2013-present). Dr. Kirkici was a Member on the Publication Services and Products Board (PSPB)-Strategic Planning Committee (2016 and 2012-2014); Member-at-Large on the IEEE Publication Services and Products Board (2011-2016) and served as Vice President of IEEE Sensors Council (2014-2015), Treasurer and Finance Chair of IEEE PSPB (2011-2014). She was the President of IEEE Dielectrics and Electrical Insulation Society (2009 and 2010), and served on many other IEEE units’ and conferences’ boards and committees.