Investigative Study On The AC And DC Breakdown Voltage of Nanofluid From Jatropha –Neem Oils Mixture For Use In Oil-Filled Power Equipment.

This paper investigated the feasibility of developing alternative insulating nanofluid from a mixture of Jatropha and Neem oils into which compositions of 0.2wt% to 1.0wt% of titanium oxide nanoparticles were dispersed. FTIR, SEM-EDX and XRD analysis of Titanium oxide nanoparticles were carried out. The DC and AC breakdown voltages were measured and analysed using Weibull statistical tool. In the Weibull statistical analysis, it was observed that the characteristic breakdown field strength of PJO is higher relative to PNO and has slight differences compared to the PJNO sample. With the dispersion of TiO2 nanoparticles, the characteristic breakdown strength improved as compared with the base oil. Furthermore, the developed Jatropha-Neem mixture nanofluid recorded characteristic breakdown field strength that is much higher compared to that of the mineral oil sample. The JNNF sample possessed the highest characteristic breakdown strength among prepared nanofluids which indicates that the characteristic breakdown strength of the oil samples has been improved considerably with the dispersion of TiO2 nanoparticles. The results have shown the viability of Jatropha-Neem nanofluid as insulating oil for use in oil-filled power equipment.

The Development of SF6 Green Substitute Gas

Due to its high greenhouse effect, the use of SF6 as the main insulating gas is restricted in the electric power field. Along with the aim of environmental protection, the search for new alternative gases with a lower greenhouse effect and higher insulation strength has received a lot of attention. The properties of alternative gases have a vital impact on the performance of medium-voltage power distribution equipment. Firstly, based on the existing liquefaction temperatures of SF6/N2, SF6/CO2, and SF6/CF4, the calculated liquefaction temperatures were expanded to 0.7 MPa. Combining the Antoine vapor-pressure equation and the basic law of vapor–liquid balance, the vapor pressures of SF6/N2, CF3I/N2, c-C4F8/N2, C4-PFN/N2, C4-PFN/CO2, and C5-PFK/CO2 were obtained. Secondly, the critical breakdown field strength was analyzed for C4-PFN/CO2, C5-PFK/CO2, SF6, CF3I/N2, C5-PFK/Air, and c-C4F8/N2. Finally, the GWPs of SF6/N2, C4-PFN/N2, C4-PFN/CO2, C5-PFK/CO2, and C5-PFK/N2 were discussed. The results show that the liquefaction temperature gradually decreases as the pressure rises; SF6/N2 has the highest vapor pressure at −5 °C; the critical breakdown field strengths of several mixtures are higher than that of SF6.

Research on the Influence of Typical Soil Parameters on Critical Breakdown Field Strength and Residual Resistivity Based on Discharge Topography

Partial discharge of soil occurs when a lightning current enters the ground, and the strength of partial discharge is closely related to the magnitude of its critical breakdown field strength. Therefore, how to accurately obtain the variation law of the typical soil critical breakdown field strength and residual resistivity is the key to realizing the safe operation of the grounding devices and cables in the ground. This paper first selects a variety of typical soils to study the influence of various factors on the morphology of the discharge channel, and then studies the calculation methods of the soil critical breakdown field strength and residual resistivity under the introduction of different discharge channel morphologies and structures, and further discusses the reason why typical soil media factors have a small impact on the critical breakdown field. The experimental results show that under the same conditions, the critical breakdown field strengths of different soils from small to large are sand soil, loam soil and Yellow cinnamon soil. The largest ratio of residual resistivity to initial resistivity of the three soils is sand soil.

Investigation of Electrical Properties of BiFeO3/LDPE Nanocomposite Dielectrics with Magnetization Treatments

The purpose of this paper is to study the effect of nano-bismuth ferrite (BiFeO3) on the electrical properties of low-density polyethylene (LDPE) under magnetic-field treatment at different temperatures. BiFeO3/LDPE nanocomposites with 2% mass fraction were prepared by the melt-blending method, and their electrical properties were studied. The results showed that compared with LDPE alone, nanocomposites increased the crystal concentration of LDPE and the spherulites of LDPE. Filamentous flake aggregates could be observed. The spherulite change was more obvious under high-temperature magnetization. An agglomerate phenomenon appeared in the composite, and the particle distribution was clear. Under high-temperature magnetization, BiFeO3 particles were increased and showed a certain order, but the change for room-temperature magnetization was not obvious. The addition of BiFeO3 increased the crystallinity of LDPE. Although the crystallinity decreased after magnetization, it was higher than that of LDPE. An AC test showed that the breakdown strength of the composite was higher than that of LDPE. The breakdown strength increased after magnetization. The increase of breakdown strength at high temperature was less, but the breakdown field strength of the composite was higher than that of LDPE. Compared with LDPE, the conductive current of the composite was lower. So, adding BiFeO3 could improve the dielectric properties of LDPE. The current of the composite decayed faster with time. The current decayed slowly after magnetization.

Effect of Acetylated SEBS/PP for Potential HVDC Cable Insulation

Blending thermoplastic elastomers into polypropylene (PP) can make it have great potential for high-voltage direct current (HVDC) cable insulation by improving its toughness. However, when a large amount of thermoplastic elastomer is blended, the electrical strength of PP will be decreased consequently, which cannot meet the electrical requirements of HVDC cables. To solve this problem, in this paper, the inherent structure of thermoplastic elastomer SEBS was used to construct acetophenone structural units on its benzene ring through Friedel–Crafts acylation, making it a voltage stabilizer that can enhance the electrical strength of the polymer. The DC electrical insulation properties and mechanical properties of acetylated SEBS (Ac-SEBS)/PP were investigated in this paper. The results showed that by doping 30% Ac-SEBS into PP, the acetophenone structural unit on Ac-SEBS remarkably increased the DC breakdown field strength of SEBS/PP by absorbing high-energy electrons. When the degree of acetylation reached 4.6%, the DC breakdown field strength of Ac-SEBS/ PP increased by 22.4% and was a little higher than that of PP. Ac-SEBS, with high electron affinity, is also able to reduce carrier mobility through electron capture, resulting in lower conductivity currents in SEBS/PP and suppressing space charge accumulation to a certain extent, which enhances the insulation properties. Besides, the highly flexible Ac-SEBS can maintain the toughening effect of SEBS, resulting in a remarkable increase in the tensile strength and elongation at the break of PP. Therefore, Ac-SEBS/PP blends possess excellent insulation properties and mechanical properties simultaneously, which are promising as insulation materials for HVDC cables.

Dielectric and AC Breakdown Properties of SiO2/MMT/LDPE Micro–Nano Composites

Low-density polyethylene (LDPE) is an important thermoplastic material which can be made into films, containers, wires, cables, etc. It is highly valued in the fields of packaging, medicine, and health, as well as cables. The method of improving the dielectric property of materials by blending LDPE with inorganic particles as filler has been paid much attention by researchers. In this paper, low-density polyethylene is used as the matrix, and montmorillonite (MMT) particles and silica (SiO2) particles are selected as micro and nano fillers, respectively. In changing the order of adding two kinds of particles, a total of five composite materials were prepared. The crystallization behavior and crystallinity of five kinds of composites were observed, the εr and tanδ changes of each material were investigated with frequency and temperature, and the power frequency (50 Hz) AC breakdown performance of materials were measured. The differential scanning calorimetry (DSC) and X-ray diffraction (XRD) results show that the crystallinity of the composites is higher than that of LDPE. Experimental data of dielectric frequency spectra show that the dielectric constants of micro–nano composites and composites with added MMT particles are lower than LDPE, the dielectric loss of composites can be improved by adding MMT particles. The experimental data of dielectric temperature spectra show that the permittivity of SiO2-MMT/LDPE is still at a low level under the condition of 20~100 °C. In terms of breakdown field strength, the SiO2/LDPE composite material increased by about 17% compared with the matrix LDPE, and the breakdown field strength of the materials SiO2-MMT/LDPE and MMT-SiO2/LDPE increased by about 6.8% and 4.6%, respectively.

Excellent energy storage properties and stability of NaNbO3-Bi(Mg0.5Ta0.5)O3 ceramic by introducing (Bi0.5Na0.5)0.7Sr0.3TiO3

NaNbO3-based energy storage ceramics have the characteristics of high breakdown field strength (Eb) with large energy storage density (Wrec). However, due to the large hysteresis loss (Wloss) under high electric...

The Research of Conductivity and Dielectric Properties of ZnO/LDPE Composites with Different Particles Size

Nanocomposites exhibit a high dielectric strength, whereas microcomposites exhibit a high thermal conductivity. In this study, good insulating materials were developed on the basis of the synergetic effect of micro- and nanoparticles, which were used as inorganic fillers. With a double-melting blend, nano-ZnO/low density polyethylene (LDPE), micro-ZnO/LDPE, and micro-nano-ZnO/LDPE composites were prepared, according to the scanning electron microscope test, polarization microscope test, conductivity test, breakdown test, and dielectric spectrum test, the dielectric property of micro-nano-ZnO/LDPE was explored. The SEM test results showed that by adding a suitable proportion of ZnO particles, the inorganic particles could disperse uniformly without reuniting. The PLM test results showed that the micro- and nano-ZnO particles adding decreased the crystal size. The arrangement was regular and tight. The macroscopic results showed that the mass fraction of nanoparticles and microparticles were 3% and 2%, the samples conductivity was the lowest. The breakdown field strength of the nanocomposites increased. The breakdown field strength of nanocomposites with 1%, 3%, and 5% nanoparticle contents were 5%, 15%, and 10% higher than that of pure LDPE. The addition of inorganic particles resulted in new polarization modes: Ionic displacement polarization and interfacial polarization. The ZnO/LDPE composites exhibited a higher dielectric constant and dielectric loss factor than pure LDPE. However, with the increasing frequency, it took considerable time to attain interfacial polarization in the nanocomposite and micro-nanocomposite, thus decreasing the dielectric constant.