Enhancing dipole polarization has been demonstrated as an effective approach to increase the dielectric constant of polymer dielectrics and thus to improve their discharged energy density for energy storage applications in electrical power and electronic systems. However, further optimization to get a higher dielectric constant and lower polarization loss hinges upon a more insightful understanding of the dynamics of dipole relaxation. Here, we demonstrate an approach, based on the Dissado-Hill dielectric response model, to probe the dynamics of dipole polarization in an all organic polythiourea (PDTC-HK511) composed of p-phenylene diisothiocyanate (PDTC) as rigid segments and Jeffamine® HK511 as flexible segments. Our results reveal that PDTC-HK511 possesses strong subglass transition β and γ relaxation processes in conjunction with the quasi-DC diffusion process at relatively high temperature and a low frequency range. The γ relaxation enhances the dielectric constant by 20%–25% but causes no apparent loss at the operating temperature and frequency conditions due to the high flexibility and short relaxation time of the dipole orientation. In comparison to β relaxation, the weak interactions and much shorter relaxation time of dipoles in γ relaxation evidenced the large flexibility of dipole movement. This work provides deeper insight into the dipole movement and aids future rational designs of polymers for dielectric energy storage.

This paper serves as a comprehensive “starter pack” for electrical diagnostic methods for power transformers. It offers a thorough review of electrical diagnostic techniques, detailing the required instrumentation and highlighting key research directions. The methods discussed include frequency response analysis, partial discharge testing, dielectric dissipation factor (tan delta), direct current (DC) insulation resistance, polarization index, transformer turns ratio test, recovery voltage measurement, polarization–depolarization currents, frequency domain spectroscopy, breakdown voltage testing, and power factor and capacitance testing. Additionally, the paper brings attention to less-explored electrical diagnostic techniques from the past decade. For each method, the underlying principles, applications, necessary instrumentation, advantages, and limitations are carefully examined, alongside emerging trends in the field. A notable shift observed over the past decade is the growing emphasis on hybrid diagnostic approaches and artificial intelligence (AI)-driven data analytics for fault detection. This study serves as a structured reference for researchers—particularly those in the early stages of their careers—as well as industry professionals seeking to explore electrical diagnostic techniques for power transformer condition assessment. It also outlines promising research avenues, contributing to the ongoing evolution of transformer diagnostics.

Power systems are experiencing a significant transformation with the implementation of emerging technologies to face 21st-century challenges such as decarbonization, digitization, and decentralization. The penetration of renewable energy is increasing worldwide, and initiatives such as distributed energy resource (DER)-based microgrids play a vital role in generating electrical power with fewer environmental impacts.

A comparative study of the space charge behavior under voltage polarity reversal in cross-linked polyethylene (XLPE) and ethylene propylene rubber (EPR) in the presence of thermal gradient was conducted. For power cable under load conditions, a temperature gradient is established across the cable insulation. Due to the resistive grading under high voltage direct current, such thermal gradient will result in the accumulation of space charge. A modified pulsed-electroacoustic system was developed so that the space charge behavior in thin films under thermal gradient can be investigated. Moreover, the role of degassing process on both XLPE and EPR was investigated. The study indicates a large amount of space charge accumulation in XLPE results in field enhancement during polarity reversal, while it is not observed in EPR.

The innovation of materials with disruptive properties can be efficiently guided by improved physical understanding of material design principles. The design of a polymeric insulation depends on the desired requirements of the specific application, which, in the case of DC cable insulation, can be stated in terms of the following properties: controlled electrical conductivity, low space charge accumulation and high breakdown strength. Full characterization and detailed understanding of these properties as well as their correlation and balance may bring the ability to engineer needed dielectric properties for using as DC cable insulation. The aim of this paper is to identify the optimal DC insulation design space and to develop a formalism of the correlation between the conductivity and space charge, guided by a relatively simple model based on two physical parameters, activation energy (ξ) and mean trap separation (λ). With respect to implications for practical material design, the study demonstrates that a polymer material with activation energies in the range of 0.4 to 0.5 eV with relatively high trap density (N) (N= λ-3 , λ=1nm, N=1E+27 m-3) can be suitable for HVDC cable insulation.