Papers by Keyword: Breakdown Strength

Abstract: The development of energy storage capacitors with high dielectric constant and good stability has been focused on by researchers due to many issues regarding environmental protection and energy conservation. Barium-Strontium Titanate based ceramic capacitors are widely used for energy storage applications due to their attractive dielectric properties. In this study, (Ba_0.90Sr_0.10) TiO₃ based capacitors were produced, and the influence of additives i.e. CaZrO₃, MnCO₃, CeO₂, ZnO, and Nb₂O₅ was investigated. The parameters of all the fabrication processes have been optimized to get defect-free green and sintered samples. The defect-free green parts were sintered at 1380°C for 2 h and perovskite structure was confirmed by XRD profiles. The grain size was refined from 25 μm to 08 μm analyzed by scanning electron microscopy (SEM). The capacitor was tested at 40 KV successfully and capacitance of 2.0 nF was measured at this high voltage. The results showed that high-voltage capacitors can be fabricated with enhanced energy storage.

Abstract: Dielectric elastomer (DE) technology are used in several applications for example generator, sensor and actuator. One of the major factors that limits the DE performance is premature electrical breakdown. Compositing is the example that have been reported to increase the breakdown strength. In this study polydimethylsiloxane (PDMS) film will be incorporated with two different fillers which are titanium dioxide (TiO₂) and zinc oxide (ZnO). Both metal oxides will be calcined up to 300°C before they are added to the PDMS elastomer as fillers. The results show that the calcined TiO₂ and ZnO that incorporated in PDMS films show significant increase of breakdown strengths. Meanwhile, the calcined TiO₂ PDMS film give higher breakdown strength as comparison to the calcined ZnO counterpart.

Abstract: A high-temperature poly (m-phenyleneisophthalamide) (PMIA) dielectric composite was successfully manufactured with functionalized BN (fBN) fillers. Due to effective modification by KH-550, fBN particles evenly dispersed in PMIA matrix. The dielectric property, breakdown strength and thermal conductivity of PMIA/fBN dielectric composite were researched. The consequences indicate that fBN fillers can not only decrease the dielectric loss but also enhance the breakdown strength of PMIA/fBN dielectric composites. Furthermore, owing to the generated heat transfer pathways by fBN particles, the thermal conductivities improved from 0.23 W·m^-1·K^-1 of fBN-0 to 0.86 W·m^-1·K^-1 of fBN-30, demonstrating a significant improvement. These results present a novel method for fabricating high-temperature PMIA/fBN dielectric composites with improved breakdown strength and thermal conductivity.

Abstract: Transformer is one of the major component, which is the most important device in power system. Their lifetime depends upon liquid insulation that help transfer the heat out of its winding inside of transformer. Transformer oil uses mineral oil that is the most commonly used has very slow process on decomposition and non-biodegrade. This paper presents the investigation on breakdown voltage of two types of natural ester oils, including palm oil and soy bean based-on ZnO nanofluids. Nanofluids that use nanoparticles modified by use of surfactant that are suspended by process of sonication. Different fraction of nanoparticles were investigated from 0.1% - 0.5% by weight. The breakdown voltage were measured according to ASTM D877. The voltage breakdown strength increased significantly when nanoparticles were added in oils. The obtained results will enable transformer industry to develop liquid insulation dielectric for use in transformer in the future.

Abstract: In high voltage direct current (HVDC) cable accessories, there is a large difference of conductivity between crosses linked polyethylene (XLPE) and liquid silicone rubber (LSR), especially considering the presence of temperature gradient and the changing of operating temperature. In this paper, nano silicon carbide (SiC) was adopted to prepare five kinds of nanocomposites with filler fractions of 1%, 2%, 3%, 4% and 5%, respectively. The conductivity and DC breakdown strength of SiC/LSR nanocomposites were measured under different temperatures. The results show that the nano SiC doping does not has the great influence on LSR DC breakdown strength, and the nano SiC doping can improve the conductivity of LSR effectively, which can realize the conductivity matching between the LSR and XLPE to homogenize the electric field distribution in cable accessory.

Abstract: Thermoplastic elastomer (TPE) nanocomposites based on 70:30 of linear low density polyethylene (LLDPE) and silicone rubber (SR) filled with nanosilica (SiO₂) and nanoboron nitride (BN) was prepared. The effect of different types of nanofiller and sequence of blending on dielectric breakdown strength, dielectric properties and morphological properties of the blend was evaluated. The results showed that the presence of nanofiller improved the dielectric strength of LLDPE/SR. BN filled system had better dielectric strength as compared to SiO₂ filled system. The addition of nanofillers also increased dielectric constant and dielectric loss of the blends. The sequence of blending significantly affected the properties of the material. The indirect blending (sample prepared master batch of SR/nanofiller) showed higher dielectric strength compared to the sample prepared through direct blending. The result was explained through SEM observation which showed the presence of fewer interfaces in the indirect blending sample, thus resulting in less weak points. This would have resulted in higher dielectric strength compared to direct blending sample which had various interfaces. The sample prepared through direct blending also showed remarkably higher dielectric contant and loss which is not suitable for insulator.

Abstract: In this article, epoxy-based dielectric materials for solid insulator were investigated. First, epoxy-based polymeric samples with different permittivities were prepared by incorporating a mixture of two fillers (Al₂O₃ and SrTiO₃) into epoxy matrix. Then, dielectric properties were characterized for the epoxy-based samples by using a dielectric spectrometer with varied frequency. Finally, breakdown tests were performed under AC voltage to characterize the breakdown strength of the dielectric material. Results indicated that the permittivity (dielectric constant) of epoxy-based materials can be adjusted only by changing the mixing ratio of two types of fillers. On the other hand, the obtained dielectric materials showed acceptable breakdown strength with the present amounts of fillers.

Abstract: Insulating properties of package for ultrahigh-voltage, high-temperature devices have been investigated. While all the packages have enough insulating strength at room temperature, deterioration of the insulating property at high temperature has been found with some packages. The authors have found that this deterioration is attributed to degrade the insulation property of AlN ceramics for DBC substrate at high temperature and that there is a various degree in the deterioration.

Abstract: For energy storage devices such as capacitances, pulsed power applications and other any electronic systems, high permittivity and high breakdown strength (BDS) are necessary for dielectric materials used in high energy storage capacitors. Ba_0.4Sr_0.6TiO₃ nano-powders were directly synthesized from solution and then wrapped by a thin surrounding shell with composition of zinc oxides dopants in aluminum oxides. This core-shell structure was characterized by a conjunction of XRD, and TEM analysis. The core-shell nanoparticles were pressed into pellets with 10 mm diameter and then sintered at different temperature in air. The specimen coated with 2.0wt% compounds of aluminum oxides doped with zinc oxides showed the maximum breakdown strength of 475kV/cm and the energy storage density of 4.7J/cm3 while the tanδ was only 0.002, whereas the uncoated Ba_0.4Sr_0.6TiO₃ was only 86.9kV/cm, 0.23J/cm3 and 0.005, respectively. And the energy storage density and the BDS decreased when the shell content was more than 2.0wt%.

Abstract: In order to get a deep understanding of the effect of internal electrical field on the electrical breakdown properties of contact materials, two kinds of W-Cu and Cr-Cu joints were prepared in a vacuum sintering furnace. The vacuum breakdown tests were respectively performed at the interface of two joints and pure metal ends in an arc extinguishing chamber, and the surface morphologies after electrical breakdown 50 times were characterized by a scanning electron microscopy equipped with an energy dispersive spectroscopy. The results show that the breakdown strength at the interface is much larger than that of pure metal ends, and the breakdown site deviates from the interface. It is suggested that the existence of internal electrical field at the interface of two contact metals changes the electronic structure, and, thus, the electrical breakdown behavior is influenced.