Space-Charge Modulated Electrical Breakdown in Polyethylene Nanodielectrics: Its Relation to Deep Traps in Interaction Zones (original) (raw)
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Composites Science and Technology, 2019
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Space Charge Trapping and Conduction in Low-Density Polyethylene/Silica Nanocomposite
Japanese Journal of Applied Physics, 2012
The high field conduction and space charge distribution were investigated in low-density polyethylene (LDPE) and LDPE/silica nanocomposites filled with various concentrations of nanosilica. The results indicate that nanosilica could effectively suppress space charge accumulation at nanofiller concentrations from 0.1 to 5.0 wt %. However, the conduction current at a high field significantly increases at low concentrations from 0.1 to 0.5 wt % and remarkably reduces at high concentrations from 0.5 to 5.0 wt %. It is shown that the trap depth corresponding to the time from 2 to 3600 s significantly decreases at low nanofiller concentrations from 0.1 to 0.5 wt %. However, the depth of deep traps corresponding to the time from 100 to 3600 s increases with the increase in nanofiller concentration from 0.5 to 5.0 wt %. Moreover, the depth of shallow traps corresponding to the time from 2 to 100 s increases at concentrations from 0.5 to 2.0 wt %, and then it decreases at concentrations from 2.0 to 5.0 wt %. In addition, the apparent mobility varies with the modification of trap depth caused by the introduction of nanofiller. The threshold field E {t for remarkable charge injection and E t{c proportional to the total trap density H are significantly lower in the nanocomposite with a low nanosilica concentration, i.e., 0.1 and 0.5 wt %, while both of them increase at concentrations from 0.5 to 5.0 wt %. It is considered that the impurity effect is greater than the nanofiller effect at a low nanofiller concentration. The deep trap is speculated as the chemical trap in the interface of the nanofiller bonding strongly with the polymer chain, while the shallow trap may be related to the chemical trap in the weakly bonded interface. It is clear that the space charge behavior and conduction are significantly affected by modification of the trap depth and density distribution owing to the introduction of nanofiller.
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...
Space charge behavior at physical interfaces in cross-linked polyethylene under DC field
IEEE Transactions on Dielectrics and Electrical Insulation, 2000
Space charge behavior at physical interfaces in cross-linked polyethylene (XLPE) films subjected to a dc field has been investigated as a function of the nature of the interfaces using the pulsed electro-acoustic technique. Aluminum, gold and carbon black-loaded polyethylene were used as electrodes to investigate space charge build-up in a single dielectric layer. A sandwich structure constituted by two dielectric films of the same nature was used to study the charging propensity of the dielectric/dielectric interface. Samples with uncharged and charged interfaces were investigated. The time dependence of the space charge distribution was subsequently recorded at different temperatures under field (polarization) and short circuit conditions (depolarization). Charge injection rather than ionic species migration is seen to control space charge distribution in single and double-layer samples in agreement with the storage conditions of the XLPE films. It is shown that the sign and distribution of the space charge depend drastically on the nature and the polarity of the electrodes and that dielectric/dielectric interfaces behave differently depending on the sign of the charge, providing deeper traps for positive charge carriers.
Journal of Physics D: Applied Physics, 2018
Nanodielectrics have been expected to improve the electrical performance and considered as dielectrics for the future. It has been recognized that the electrical performance is close related to charge dynamics in the dielectrics material. However, the mechanism of charge dynamics in the interphase of nanodielectrics has not been fully understood, which cause the difficulty in understanding the effect of nanoparticle loading ratios and electric fields applied on the electrical properties. Recently, a model based on the tunneling process with the presence of deep traps has been suggested as one of the conceivable candidates for explaining charge dynamics in nanodielectrics, but the related experiment results are not discussed with tunnelling process. In this paper, the measurements including isothermal surface potential decay and space charge are conducted for the blend polyethylene incorporated with the untreated silica nanocomposites. According to the experimental observation compared with the unfilled blend polyethylene, the electrical properties of nanocomposites with high loading ratios of 2 wt%, 5 wt% and 10 wt% are worsened such as facilitated space charge accumulation and injection, and faster charge carriers transport. On the other hand, regarding the nanocomposites with the low loading ratios of 0.5 wt%, it was observed that slow transport of charge carriers, and suppressed space charge accumulation and injection. The effect of the lower and higher electric field on the electrical properties of the nanocomposites was similar for the low and high loading ratios. The tunnelling process associated with deep traps can effectively explain these observed phenomena of nanocomposites, it is therefore suggested for further explaining the electrical properties and charge dynamics in the nanodielectrics.
The Effects of Nano Fillers on Space Charge Distribution in Cross-Linked Polyethylene
International Journal of Electrical and Computer Engineering (IJECE), 2017
The performance of polymeric insulation will be distorted by the accumulation of space charge. This will lead to local electric field enhancement within the insulation material that can cause degradation and electrical breakdown. The introduction of nanofillers in the insulation material is expected to reduce the space charge effect. However, there is a need to analyze potential nanofillers to determine the best option. Therefore, the objective of this research work is to examine two types of nanofillers for Cross-Linked Polyethylene (XLPE); Zinc Oxide (ZnO) and Acrylic (PA40). The effects of these nanofillers were measured using the Pulsed-Electro Acoustic (PEA) method. The development of space charge is observed at three different DC voltage levels in room temperature. The results show that hetero charge distribution is dominant in pure XLPE materials. The use of both nanofiller types have significant effect in decreasing the space charge accumulation. With nanofillers, the charge profile changed to homo-charge distribution, suppressing the space charge formation. Comparison between both the nanofillers show that PA40 has better suppression performance than ZnO.
AIP Advances, 2016
This work studies the correlation between secondary electron emission (SEE) characteristics and impulse surface flashover in polyethylene nanodielectrics both theoretically and experimentally, and illustrates the enhancement of flashover voltage in low-density polyethylene (LDPE) through incorporating Al 2 O 3 nanoparticles. SEE characteristics play key roles in surface charging and gas desorption during surface flashover. This work demonstrates that the presence of Al 2 O 3 nanoparticles decreases the SEE coefficient of LDPE and enhances the impact energy at the equilibrium state of surface charging. These changes can be explained by the increase of surface roughness and of surface ionization energy, and the strong interaction between nanoparticles and the polymer dielectric matrix. The surface charge and flashover voltage are calculated according to the secondary electron emission avalanche (SEEA) model, which reveals that the positive surface charges are reduced near the cathode triple point, while the presence of more nanoparticles in high loading samples enhances the gas desorption. Consequently, the surface flashover performance of LDPE/Al 2 O 3 nanodielectrics is improved.
Space charge dynamic at the physical interface in cross-linked polyethylene under DC field
IEEE Transactions on Dielectrics and Electrical Insulation, 2000
In this paper the behavior of positive charge formed in the vicinity of the Semi-conducting sheet anode at room temperature and under applied dc has been investigated just after the reversal of the sample, and when the sample was combined with another sample without pre-stressing using the pulsed electro acoustic (PEA) method. The results suggest that the PEA system can only show the net charge density, and the space charge distribution is drastically changed when the sample is reversed just after the removal of the applied voltage (depolarization), or when this sample was combined with another without pre-