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Erosion of weathershed composite materials is one of the key failure modes in outdoor insulators and it can adversely impact on the reliability of power system networks. To enhance resistance against erosion and dry band arcing, inorganic particles are often added to base polymeric matrix. This paper investigates the erosion resistance of micron-AlN and hybrid micron-AlN + nano-silica filled silicone...
Nano-doping has a significant effect on dielectric and electrical insulation for polymer dielectrics. Pure polyimide 100HN and nano-doping polyimide 100CR from DuPont Company are adopted to conduct short-term breakdown and long-term corona-resistant experiments. The results show that, the short-term breakdown strength of 100CR is 6.4% lower than 100HN. For long-term corona resistance, the corona-resistant...
Silicone rubber is widely used in power equipment such as cable joint. In order to get better performance of insulator, it is significant to evaluate the insulation condition of aged silicone rubber insulators. Thus in this paper, surface potential decay measurement has been applied to investigate the performance of pristine and aged silicone rubber. Pristine and aged silicone rubber samples are charged...
The influence of ozone surface treatment on surface flashover performance of epoxy resin/AhO3 microcomposites was investigated. Epoxy resin/AhO3 microcomposite samples with a diameter of 50 mm and a thickness of 1 mm were prepared and treated by ozone for various periods. Surface potential decay, surface conductivity, secondary electron emission coefficient, and surface flashover voltage in SF6 of...
Epoxy resin as a typical electrical insulation material has been widely applied in the power equipment. However, the electrical properties of epoxy resin are strongly affected by the surface charge accumulation. One way to solve the surface charge accumulation may be to use the nonlinear resistive field grading nanocomposites. In this paper, we aim to study the effect of ZnO nanoparticles on the surface...
This paper presents the fundamental characteristics of the electronic structures of silicone rubber (uncured SR) and cured (crosslinked) SR molecules. Localized states and trapping sites are evaluated by the molecular orbitals (MOs) and the density of state (DOS). The introduction of vinyl groups slightly changes the energy level distribution and introduces the electron-localized states (shallow trapping...
A method is proposed to calculate the density of deep traps formed in interaction zones based on mesoscopic structure and double electric layer of polymer nanocomposites. Then a space charge modulated breakdown model is utilized to investigate electrical breakdown property and its relation with deep traps in interaction zones. It is found that deep traps formed around independent interaction zones...
ZnO-based varistors have been widely applied in surge protection devices because of their excellent nonlinear current-voltage (I-V) characteristic and energy absorption ability. Manganese is always added into ZnO-based varistors in order to enhance the nonlinear characteristic of materials. In the present work, the dielectric properties of Mn-doped ZnO-Bi2O3 varistors at extremely low temperatures...
Thermal degradation due to dry band arcing in the discharge region causes tracking and erosion failure of composite insulators. This work investigates resistance against tracking and erosion of silicone rubber filled with micron sized aluminum nitride (AlN) and boron nitride (BN) particles. Their performances are evaluated by comparing the average tracking length, eroded mass and thermal distribution...
To satisfy the rapid development of energy requirements, power transmission with higher voltage must be adopted. The large improvement in transmission voltage needs more excellent power equipment and better materials to meet its insulation requirement. Polytetrafluoroethylene (PTFE) nozzle used in high voltage circuit breaker faces the issue of breakdown and arc ablation, and thus superior performance...
This paper considers the optimal switching time control problem for discrete-time switched autonomous systems. The controlled parameter consists of the switching times, and the cost functional is defined on the state and performance cost functions are different in different time-intervals. Based on calculus of variations, an approach to finding the optimal switching times is proposed. Firstly, we...
Among all the carbon fillers, graphene has attracted tremendous research interest for its special two-dimensional and single-atom-thick structure. High electrical, mechanical and optical properties of graphene have been proved. By adding graphene as filler into polymer, it is possible to achieve a new composite with unique physical, electrical and thermal properties. In this paper, epoxy/graphene...
Dissolved gas analysis (DGA) is the most effective method to detect incipient faults in power transformers. It uses the concentrations of various gases dissolved in the transformer oil due to decomposition of the oil and paper insulation. Gases such as hydrogen, methane, acetylene, ethylene, and ethane are generated as a results of oil decomposition, while carbon monoxide and carbon dioxide are generated...
Trap and polarization greatly affect dielectric breakdown and surface flashover behavior of insulating materials. Trap and polarization may be modified by electron beam irradiation via breaking polymeric molecular chains or triggering cross-linking. Polyethylene terephthalate (PET) with a thickness of 75 μm from DuPont was used to investigate the modifications of trap and polarization by electron...
Spectroscopy is a powerful non-destructive technique that utilizes electromagnetic radiation interaction effect to determine the energy level and structure of atomic or molecular substance. Spectroscopy technique has been successfully used to quantify some power transformer condition monitoring parameters such as Furan and oil interfacial tension value. This paper investigates the feasibility of extending...
This paper investigates the space charge distribution and external current performance of Ethylene Propylene Diene Monomer (EPDM) film simultaneously by an improved integrated PEA system. Through switching the space charge and current measurement circuits, the space charge and external current were detected alternately during the electric field of 60 kV/mm and 80 kV/mm. Small amounts of homocharges...
The interior distributions of electrical and dielectric properties of ZnO varistor at initial aging stage are investigated. Two commercial varistors at different aging stages were compared. These two varistors were cut into slices along the axial direction, and then the variations of varistor slices' electrical and dielectric performances were obtained. The results show that the interior performance...
ZnO varistors have been extensively used against transient surges because of the excellent nonlinearity. ZnO varistors are obtained by sintering semiconducting ZnO powder with small amount of metal oxide additives. Amongst, Mn-doping is effective in the enhancement of the nonlinearity. In this paper, the relationship between the microstructure, the electrical and dielectric properties of Mn-doping...
High-frequency harmonics occur in converter transformers, which may lead to unexpected breakdown of oil impregnated paper insulation under ac-dc combined voltages with high frequencies. Here in this paper, the breakdown characteristics of oil impregnated paper insulation under ac-dc combined voltages in frequencies of 50∼600 Hz were experimentally investigated. After considering the characteristics...
Nanodielectrics have been an emerging research topic in the field of electrical insulation due to their potential wide ranges of applications. Loading nanoparticles into polymer, the properties of composite can be improved, such as, space charge suppression, increases in surface flashover voltage and breakdown strength. However, it has been observed that composite properties have a strong relationship...
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