Diagnostic methodologies are of fundamental importance for operational strategies of electrical devices, both in the power grid and in industrial applications. This paper reports about a novel approach based on partial discharge analysis applied to high voltage electrical insulation. Especially dynamics of charges deposited by partial discharges is explored applying a chopped sequence. The applications refer to microvoids occurring inside solid insulating systems or at the interfaces, such as delaminations at the electrodes. The experiments were carried out on embedded voids having distinctive wall dielectric materials. The underlying physical phenomena of post discharge charge transport are analyzed. The assessment is performed using phase-resolved partial discharge patterns acquired applying a chopped sequence. The chopped partial discharge (CPD) method provides quantitative insight into post discharge charge decay processes due to deposited and accumulated charges fluctuations. The assessment indicator is based on comparing partial discharge inception angle between chopped sequence and continuous run. The experiments have shown that materials with distinctive surface conductivity revealed adequately different charge decay time dynamics. The detailed analysis yields time constant of walls charge decay for insulating paper equal to 12 ms and cross-linked polyethylene 407 ms. The CPD method may be further used to investigate streamer physics inside bounded cavities in the form of voids. The presented method provides a quantitative approach for charge non-invasive decay assessment and offers high potential in future diagnostics applications.

The life of Jerzy Ignacy Skowronski, Professor of High Voltages, Dean of the Faculty of Mechanical and Electrical Engineering and the first Dean of the Electrical Faculty of the Wrocław University of Science and Technology, member of the real Polish Academy of Sciences and President of the Wrocław Scientific Society, founder of the Wrocław Scientific School of Electrical Materials, was described. Documents contained in the Archives of the Wrocław University of Science and Technology, works published by Jerzy I. Skowronski, previously published publications on his scientific merits written by his former Ph.D. students and information from his grandson Jan Paweł Skowronski were used. The author's intention was to show unknown facts from the life of the Professor and his works unknown until now.

High voltage DC insulation plays an important role, especially in power transmission systems (HVDC) but also increasingly on medium voltage levels (MVDC). The space charge behavior under DC voltage has great importance on electrical insulation reliability. This paper reports investigations of encapsulated space charge in homo-multilayer dielectric materials using the pulsed electro-acoustic (PEA) method. The charge has been introduced on the homo-layer interface by corona sprinkling prior to encapsulation. Two doses of charge density were accumulated on the dielectric surface in two types of dielectric materials Kapton and LDPE. The polarization DC voltage was applied in 2 min intervals in steps corresponding to an effective electric field strength in a range of 8-40 kV/mm for Kapton and 10-50 kV/mm for LDPE. The PEA-based detected space charge was compared at the initial, reference stage, prior to charge accumulation, and after corona sprinkling of defined charge density. The evaluation was based on the PEA time-dependent charge distributions and charge profiles referring to the DC polarization field strength. The goal of the experiment was to identify the relationship and the character of the known sprinkled and encapsulated charge inside homo-layered materials using the PEA method. According to the observations, the ratio between sprinkled charge densities is proportional to the encapsulated, charge densities measured by the PEA method on the interfacial homo-layer for the Kapton specimen. In the case of LDPE, a fast decrease of interfacial charge was observed, especially at a higher polarization field above 10 kV/mm. The encapsulation of the known charge amount can be extended to different types of multilayer material. The presented methodology might be used also for extended calibration of the PEA measurement system.