Enhanced flashover strength in polyethylene nanodielectrics by secondary electron emission modification (original) (raw)
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Surface Discharges and Flashover Voltages in Nanocomposite XLPE Samples
Engineering, Technology & Applied Science Research
DC cable insulation is a field of intensive research activity. Special attention is being given to polymer nanocomposites, as promising insulation for such cables. Relatively little is known regarding surface discharges and flashover voltages for the aforementioned materials. In this paper, a comparison is made between samples of cross-linked polyethylene insulation with added MgO nanofillers and samples of pure polyethylene w.r.t. the behavior of surface discharges and flashover voltages in arrangements of water droplets of various conductivities on the said polymeric surfaces under the influence of uniform electric fields. Experimental evidence indicates that the flashover voltages of XLPE with MgO nanofillers are higher that the ones obtained with pure PE.
Charging and Discharge Currents in Low-Density Polyethylene and its Nanocomposite
Energies, 2020
Charging and discharge currents measured in low-density polyethylene (LDPE) and LDPE/Al2O3 nanocomposite are analyzed. The experiments were conducted at temperatures of 40–80 °C utilizing a consecutive charging–discharging procedure, with the charging step at electric fields varying between 20 and 60 kV/mm. A quasi-steady state of the charging currents was earlier observed for the nanofilled specimens and it was attributed to the enhanced trapping process at polymer–nanofiller interfaces. An anomalous behavior of the discharge currents was found at elevated temperatures for both the studied materials and its occurrence at lower temperatures in the nanofilled LDPE was due to the presence of deeply trapped charges at polymer–nanofiller interfaces. The field dependence of the quasi-steady charging currents is examined by testing for different conduction mechanisms. It is shown that the space-charge-limited process is dominant and the average trap site separation is estimated at less th...
Engineering, Technology & Applied Science Research
A new class of insulating materials is the class of polymer nanocomposites. In the past twenty-five years, a lot of attention was paid to the various electrical, thermal and mechanical properties of polymer nanocomposite materials. In the present work, epoxy resin samples without and with nanoparticles (0 wt%, 1 wt%, 3 wt%, 5 wt%, and 10 wt%) are investigated regarding the surface discharges and the flashover voltages. Four different water droplet arrangements were used, with eight different water conductivities in order to see the effect of the nanoparticle.
The low surface energy of HDPE limits its industrial uses as it is not suitable for printing and adhesion. The main aim of this work is to improve the wetting properties of high-density polyethylene (HDPE) using air dielectric barrier discharge (DBD) operating at the line frequency (50 Hz). The estimation of electron temperature and electron density has been done by electrical and optical methods. The surface roughness of the control and plasma treated polymer film is analysed by contact angle (CA) measurement, surface energy measurement and scanning electron microscope (SEM) analysis. The contact angle was found to be suppressed from 93.1 0 ±2.0 0 to 64 0 ±1 0 after 10 sec of plasma treatment which implied that the surface property had changed to a hydrophilic state caused by an increase in the surface roughness.
The surface potential decay on low-density polyethylene (LDPE) has been studied after negative charge deposition by corona effect as a function of initial potential V o and charging time t c. It was found that the decay rate increases with initial potential and charging time. For high charging level, cross over phenomenon has been observed. Surface potential profile has been recorded with two different charging levels. The surface potential profile indicates the absence of lateral migration of charges along the free surface of the LDPE film and the presence of the hollow for high initial potential, which makes the bulk conduction mechanisms caused by charge injection into the LDPE film bulk, responsible for the observed surface potential decay.
Morphology Effects on Space Charge Characteristics of Low Density Polyethylene
… Journal of Applied …, 2011
Low density polyethylene (LDPE) film samples with different morphology were prepared by three kinds of annealing methods which were different in cooling rates in this study. A pulsed electro-acoustic (PEA) space charge measurement system was improved to solve the surface discharge problems for small samples applied with a high voltage. Negative direct current (DC) fields from 50 to above 220 kV/mm were applied to the samples. The influences of morphologies on space charge and space charge packet characteristics were measured by the improved high voltage withstand (HVW) PEA system. Mobility and trap depth of released charges were calculated by space charge decay. It was found that there is a different probability of space charge packet initiation under applied field from À60 to À100 kV/mm. Average velocity and mobility of the space charge packets were calculated by space charge packet dynamics. It was found that the lower cooling rate samples have higher crystallinity, more homo-charge accumulation, lower mobility and deeper trap depth. The mechanism of morphological effects on space charge phenomena have been presumed to give a plausible explanation for their inherent relationships. The morphology in the metal-dielectric interface and in the bulk is convincingly suggested to be responsible for the injection and propagation processes of space charge. A model of positive space charge initiation in LDPE samples was also suggested and analyzed. The mechanism of morphological effects and the charge injection model are well fit with the injection and propagation processes of space charge. The different effects of morphology in the metal-dielectric interface and in the bulk of polymers are stressed.
Journal of Applied Physics
This work presents a comprehensive investigation into the effects of nanoparticles and organic additives on the dielectric properties of insulating polymers using reinforced silicone rubber as a model system. TiO 2 and ZrO 2 nanoparticles (d ¼ 5 nm) were well dispersed into the polymer via a bimodal surface modification approach. Organic molecules with the potential of voltage stabilization were further grafted to the nanoparticle to ensure their dispersion. These extrinsic species were found to provide deep traps for charge carriers and exhibited effective charge trapping properties at a rather small concentration ($10 17 cm À3). The charge trapping is found to have the most significant effect on breakdown strength when the electrical stressing time is long enough that most charges are trapped in the deep states. To establish a quantitative correlation between the trap depth and the molecular properties, the electron affinity and ionization energy of each species were calculated by an ab initio method and were compared with the experimentally measured values. The correlation however remains elusive and is possibly complicated by the field effect and the electronic interactions between different species that are not considered in this computation. At high field, a super-linear increase of current density was observed for TiO 2 filled composites and is likely caused by impact excitation due to the low excitation energy of TiO 2 compared to ZrO 2. It is reasoned that the hot charge carriers with energies greater than the excitation energy of TiO 2 may excite an electron-hole pair upon collision with the NP, which later will be dissociated and contribute to free charge carriers. This mechanism can enhance the energy dissipation and may account for the retarded electrical degradation and breakdown of TiO 2 composites. Published by AIP Publishing.
Materials Research Express, 2020
Solid insulation materials are the backbone for all kinds of outdoor insulation applications. Environmental stresses degrade every outdoor insulation material with the passage of time. Internal partial discharges and external surface tracking are the two major factors governing the health of outdoor insulation. Best outdoor insulation is the one having lowest level of partial discharge and highest resistance to tracking. Improvement in tracking resistance of polymeric insulation materials has been a concern of many researchers. This study investigates the improvement in partial discharge and tracking resistance of LDPE under the effect of three different nano fillers including SiO2, TiO2, TiO2@SiO2. A very little has been reported on the effect of these nano fillers on the tracking performance of LDPE. TiO2@SiO2 is a novel core–shell nano filler. No study has reported the effect of these core–shell nano fillers on the partial discharge and tracking performance of LDPE. It has been o...
iaeme
Nanoparticles have attracted wide interest for enhancing electrical properties of polymer industrial materials as form nanocomposites, therefore, preparation new Polyethylene nanocomposites will be helpful both the manufacturers and users for enhancing electrical performance of Polyethylene applications. This paper has been enhancedelectricand dielectric characterizations of polyethylene with adding costless nanoparticlesto low density polyethylene (LDPE), and high density polyethylene (HDPE) as a base matrix. Polyethylene trapping properties are highly modified by the presence of costless nanofillers(clay, and fumed silica) nanoparticles. Also, it has been studiedexperimentally the influence of costless nanofillers(clay, and fumed silica)and their concentrations on electric and dielectric properties of polyethylene materials.Experimental comparative study has been discussed about Polyethylene nanocomposites with respect to commercial polyethylene materials to explain the effect of types and concentrations of nano-fillers for enhancing electric and dielectric Polyethylenecharacteristics.