High-k polymer nanocomposites have considerable potential in energy storage and dielectric applications because of their ease of processing, flexibility, and low cost. Core-shell nanoarchitecture strategies are versatile and powerful tools for the design and synthesis of advanced high-k polymer nanocomposites. Recent and in-progress state-of-the-art advancements in the application of core-shell nanoarchitecture strategies to design and prepare high-k polymer nanocomposites are summarized. Special focus is directed to emphasizing their advantages over conventional melt-mixing and solution-mixing methods: first, homogeneous nanoparticle dispersion can be easily achieved even in highly loaded nanocomposites; second, the dielectric constant of the nanocomposites can be effectively enhanced and meanwhile the high breakdown strength can be well-preserved; third, for nanocomposites filled with electrically conductive nanoparticles, dielectric loss can be effectively surpressed, and meanwhile a high dielectric constant can be achieved. In addition, fundamental insights into the roles of the interfaces on the dielectric properties of the nanocomposites can be probed. The last part of the article is concluded with current problems and future perspectives of utilizing the core-shell nanoarchitecture strategies for the development of high-k polymer nanocomposites.

Core-shell structured high-k polymer nanocomposites for energy storage and dielectric applications.

High-k polymer nanocomposites with 1D filler for dielectric and energy storage applications

In recent years, there is a growing interest in studying the dielectric behavior of biopolymer composites due to their potential application as a dielectric material in various electronic devices such as microchips, transformers, and circuit boards. Conducting electroactive polymer composites have also been investigated for various potential applications which include biological, biomedical, flexible electrodes, display devices, biosensors, and cells for tissue engineering. In this chapter, the preparation and dielectric behavior of various biopolymer composites is presented. These biopolymer composites generally consist of nanoscale metal nanoparticles and carbon-based nanofillers such as carbon nanotubes, graphene, graphene oxide (GO), etc., dispersed into the polymer matrix. The physical and chemical properties of these fillers and their interactions with polymers have a significant effect on the microstructure and the final properties of nanocomposites. The biopolymer composites with excellent dielectric properties show great promise as an energy storage dielectric layer in high-performance capacitor applications such as embedded capacitors. This chapter highlights some of the examples of such biopolymer composites; their processing and dielectric behavior will be discussed in detail.

Biopolymer Composites With High Dielectric Performance: Interface Engineering

DC transmission helps to solve the decentralization of distributed wind power generation and other renewable power sources to enhance system performance. But the existence of surface charges by the corona makes earlier insulation failure and plays an important role during the development of the surface flashover. The influences of the ambient temperature and the polarity reversal voltage on the surface charge and the flashover of the heat-shrinkable polymer are not completely clear. In this paper, the carrier mobility and the volume conductivity were employed to explain the temperature dependent surface charge decay results. The initial surface charge density and decay rates served for analyzing the effects of polarity reversal voltage. Furthermore, the flashover experiments of the samples charged by the polarity reversal voltage at different ambient temperatures were conducted. Obtained results show that the descending speed of the surface charge becomes faster at higher temperature. An obvious temperature dependence of the carrier mobility and the volume conductivity is observed. Moreover, the surface charges of the samples charged by the voltage with shorter reversal time decay more rapidly. The flashover voltage increases with the increasing ambient temperature because of less accumulated surface charges in this condition. Considering the accelerated surface charge decay by the increasing temperature and easier charge accumulation during the steady negative period, attentions should be paid to the design of DC insulation and the security of operation.

Effects of ambient temperature on surface charge and flashover of heat-shrinkable polymer under polarity reversal voltage

Polymeric dielectrics are employed extensively in the power transmission industry, thanks to their excellent properties; however, under normal operating conditions these materials tend to degrade and fail. In this study, samples of low-density polyethylene, polypropylene, polymethyl methacrylate, and polytetrafluorethylene were subjected to corona discharges under nitrogen and air atmospheres. The discharges introduced structural modifications over the polymer surface. From a chemical perspective, the alterations are analogous among the non-fluorinated polymers (i.e., polyethylene (PE), polypropylene (PP), and polymethyl methacrylate (PMMA)). A simulation of the corona discharge allowed the identification of highly reactive species in the proximity of the surface. The results are consistent with the degradation of insulating polymers in high-voltage applications due to internal partial discharges that ultimately lead to the breakdown of the material.

Experimental characterization of polymer surfaces subject to corona discharges in controlled atmospheres

High voltage power cables and their accessories are vital components of the electrical power network. Because of this, reliable operation over their lifetime is essential to minimize failures during service. As in-service failures most often incur very high costs, condition monitoring of high voltage cable accessories is becoming increasingly of interest and is being applied. Monitoring of partial discharge (PD) is currently the most common method implemented. This article discusses the fundamental aspects of PD and its measurement on high voltage power cable accessories. The article begins with discussing the various PD measurement techniques, which are explained and compared. Finally, the results of typical measurements on high voltage cable accessories are shown, and their consequences in operation are discussed.

An overview on the current status of partial discharge measurements on AC high voltage cable accessories

Maxwell and Felici developed the theoretical basis of geometrical stress control during the period 1846 to 1862. The first practical implementation, however, was that of Nagel in Germany in 1906 (Figure 1). He developed the socalled Nagel-bushing on the basis of conductive layers [1]. Around the same time, the Swiss professor Kuhlmann invented the refractive method [2]. His aim was to decrease the electrical stress at the points where it was highest, rather than distributing it to other areas. The famous Rogowski profile was introduced in 1923. The basic principles are the same today, although the applications have become more complex, and stress control is still an important research area in HV engineering. Developments in stress control during the last 50 years (Figure 1) have been due mainly to new materials and production processes, and modern technologies, which have made possible to create cable accessories of more compact design and to improve their reliability. These developments have included impedance stress control based on heat-shrinkable tubing, and nonlinear stress control. In both cases the driving force was the need to improve the stress-control system of cable accessories.

50 years of electrical-stress control in cable accessories

The present invention relates to a field control element for a high-voltage cable accessory. The present invention further relates to a high-voltage cable accessory (200, 300, 400) and to a method of monitoring partial discharges occurring within an insulating part of such a high-voltage cable accessory. According to the present invention, said field control element (212; 304; 406, 408) comprises an electrically insulating material that is at least partly provided with a fluorescent dye, said fluorescent dye being configured to convert a first radiation generated by an electrical discharge into a second radiation with a wavelength that is longer than the wavelength of the first radiation. A high-voltage cable accessory (200, 300, 400) has an electrically insulating part that comprises at least one field control element (212; 304; 406, 408) according to the present invention and/or and/or a further insulating element comprising a fluorescent dye.

Field control element for a high-voltage cable accessory and method of optically measuring partial discharges

An apparatus (1) for forming a sheathed cable sheath at a cable shed location or for a connection between two shielded cables (7, 8) comprises a hollow sheath body (2) with insulating material for sheathing the cable or joint (10) the cable (7, 8) and an outer layer (3), comprising electrically conductive material (31, 32), which surrounds the enveloping body (2) at least partially. The enveloping body (2) has two mutually opposite edges (21, 22), which are arranged and designed such that these after application of the enveloping body on the cable or the junction of the cable, each with a part (72, 82) of the cable or the cable in contact. At least one isolation region (41, 42) is disposed in the outer layer (3) which inhibits electrical connection between the edges (21, 22) via the outer layer.

Cold shrink sleeve for forming cladding in screened cable, has body arranged such that edges come in contact with part of cables after attaching body on cables and/or on point, and outer layer preventing connection between edges

The spout has a fluid outlet running from an inlet (5) to an outlet opening (6). A perforation unit that pierces through a fluid container is designed at an inlet pipe socket (2). The socket has an outer peripheral surface, and an inlet front surface that is tilted in an acute inclination angle opposite to a longitudinal axis of the socket. The unit has a cutting edge, which is formed from an intersection line of the front surface with the outer peripheral surface. The socket expands behind the edge, such that a breakthrough opening of the container stretches closely around the socket.

Outlet spout for cartridge system, has perforation unit with cutting edge, formed from intersection line of inlet front surface, and inlet pipe socket expanding behind edge, so that breakthrough opening of container stretches around socket

Alexander Eigner

Papers

An overview on the current status of partial discharge measurements on AC high voltage cable accessories

50 years of electrical-stress control in cable accessories

Field control element for a high-voltage cable accessory and method of optically measuring partial discharges

Cold shrink sleeve for forming cladding in screened cable, has body arranged such that edges come in contact with part of cables after attaching body on cables and/or on point, and outer layer preventing connection between edges

Outlet spout for cartridge system, has perforation unit with cutting edge, formed from intersection line of inlet front surface, and inlet pipe socket expanding behind edge, so that breakthrough opening of container stretches around socket