Half-way seminar Daniel Svensson

Daniel Svensson is a PhD student in the research group Electrical machines and power electronics, division Electric power engineering, Chalmers University of Technology

Discussion leader is Associate Professor Tord Bengtsson, Hitachi Energy

Examiner is Yuriy Serdyuk, division Electric power engineering.

Introduction:

High voltage capacitors are essential for reactive power compensation and harmonic filtering in modern electrical networks. With increasing integration of renewable energy sources and high-voltage direct current (HVDC) transmission, capacitors are exposed to extreme operational conditions, including electric fields exceeding several hundred kV/mm and harmonic-induced dielectric heating, accelerating their degradation [1]. The dielectric frequency response (DFR) method is widely used to assess the frequency-dependent dielectric properties of insulating materials. However, most commercial DFR instruments operate at relatively low voltage magnitudes, which limits their applicability for high-field scenarios.
Prior work has laid foundations for more advanced DFR systems. One method was proposed that utilizes a standard vacuum capacitor as reference to compensate for measurement errors [2]. However, the obtained accuracy depends critically on maintaining identical measurement conditions and assuming that the reference capacitor is truly lossless. Xu proposed an alternative "air reference" approach, measuring the electrode setup both with and without the test object to eliminate variations in stray capacitance [3]. This improved the consistency but also introduced practical challenges such as manual sample handling and a reduction in accuracy compared to when using vacuum capacitors as references. For thin-film capacitor materials, an additional challenge arises as contact losses at electrodes’ interfaces can be dominating the results, particularly in low-loss regimes.
Building on these insights, this work presents a high-voltage DFR system that addresses both measurement methodology limitations and practical challenges while performing high-field material characterization. The system integrates rigorous error compensation techniques with specialized sample preparation procedures to enable reliable dielectric property measurements under high electric field levels.