In this paper, a review on dielectric mixtures and the importance of numerical simulations are presented. It stresses interfacial polarization observed in mixtures. is shown that can yield different responses depending properties constituents their concentrations. Open question subject also introduced.

Knowledge about moisture content in oil impregnated paper insulation is essential when estimating remaining lifetime of power transformers. Direct evaluation rarely possible due to inaccessibility the internal system Therefore, various indirect estimation techniques are utilized. Frequency domain spectroscopy (FDS) measurements transformer belong this group. To perform high quality interpretation results FDS a good knowledge on dielectric responses pressboard and required, especially as it...

Because modern society is strongly dependent on a reliable power supply, there an urgent need to develop more high voltage insulators. While porcelain and glass have dominated insulator materials for long period of time, renewed interest in polymeric semiconducting glaze This paper provides brief description composite insulators, including discussion their benefits, aging housing materials, brittle fracture phenomenon. The also discusses the benefits using insulators with surfaces,...

The wettability of aged surfaces and the bulk naturally silicone EPDM (ethylene-propylene diener monomer) insulator housings elastomer coatings was studied. samples were taken either directly from insulators or treated by exposing them to corona discharges and/or saline pollution. results show that contact angles rubber are larger than RTV (room-temperature vulcanizing) coating surfaces, especially when aged. When exposed discharges, reduced but after exposure recover with time. insulators,...

Composite insulators are considered mature products and a broad range of insulator types is nowadays available, including line insulators, hollow-core apparatus for applications ranging from distribution voltages to the highest transmission voltages. This development has created need elaborate diagnostic methods tools determining quality composite insulators. A review on recognized faults their detection provided.

This paper presents an advanced model of the frequency response a three-phase power transformer for use in conjunction with diagnostic measurements by method analysis (FRA). The includes high- behavior laminated core and insulation through taking into account dependencies complex permittivity materials (paper, pressboard, oil) anisotropic permeability magnetic conductors. A lumped parameter circuit is used to simulate open-circuit impedance, short-circuit impedance between primary secondary...

This work presents results of bulk conductivity and surface potential decay measurements on low-density polyethylene its nanocomposites filled with uncoated MgO Al₂O₃, the aim to highlight effect nanofillers charge transport processes. Material samples at various filler contents, up 9 wt %, were prepared in form thin films. The performed show a significant impact reduction material's direct current (dc) conductivity. investigations thus focused having lowest dc Various mechanisms generation...

Effect of surface charges on dc flashover characteristics a composite polymeric insulator is studied by means experiments and theoretical calculations. The considered consisted glass fiber reinforced epoxy core covered with layer silicone rubber terminated metallic electrodes rounded smooth edges. In the experiments, was charged external corona while keeping grounded different charging levels were realized varying its intensity. A series disruptive discharge tests carried out under negative...

A comprehensive experimental investigation of XLPE and its nanocomposite with fumed silica (SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) has been performed by CIGRE Working Group D1.24, in cooperative tests conducted a number members; covering materials characterization, real imaginary permittivity, dc conductivity, space charge formation, dielectric breakdown strength, partial discharge resistance. The research is unique, since...

Fullerenes are shown to be efficient voltage-stabilizers for polyethylene, i.e., additives that increase the dielectric strength of insulation material. Such compounds highly sought-after because their use in power-cable may considerably enhance transmission efficiency tomorrow's power grids. On a molal basis, fullerenes most voltage stabilizers reported date.

Composites of LDPE filled with different amounts graphene nanoplatelets (GnP) were prepared in form films by means precoating technique and single screw melt-extrusion using two types screws, compression mixing. This manufacturing process imposes strong anisotropy on the sample's morphology, which become oriented along extrusion direction. Such orientation GnP matrix is confirmed scanning electron microscopy observations it yields unique electrical properties. As compared to pure LDPE,...

Polyethylene nanocomposites based on functionalized ZnO nano/hierarchical particles with highly effective interfacial surface area are presented, for the next generation of ultralow transmission-loss high-voltage DC insulating materials. As a service to our authors and readers, this journal provides supporting information supplied by authors. Such materials peer reviewed may be re-organized online delivery, but not copy-edited or typeset. Technical support issues arising from (other than...

Ultra-insulating polyethylene nanocomposites were achieved by appropriate MgO nanoparticle surface modification, resulting in unprecedented dispersion and 2 orders of magnitude lower conductivity.

In this article, the frequency dependent dielectric properties, ε(ω), of an “ideal” binary composite structure were investigated by using finite element method in domain. The material properties phases, i.e., permittivity, ε, and direct-current conductivity, σ, assumed to be independent. Moreover, inclusion phase was more conductive than matrix phase. inclusions infinitely long unidirectional cylinders which could hard disks two dimensions direction perpendicular cylinder direction. Three...

In a long-term outdoor test with high direct and alternating voltages, silicone ethylene propylene diene monomer (EPDM) rubber composite insulators have, at the beginning, shown performance superior to that of glass porcelain insulators. test, however, insulator has, in spite aging both types, kept its good performance, while EPDM was drastically deteriorated. order get better insight into results obtained, wettability surface structural changes were studied by drop deposition method using...

This paper explores the possibility for using frequency response analysis (FRA) technique to characterize quality of transformer insulation. For this purpose, a single-phase and three-phase lumped parameter circuit models were developed. The model represents without laminated core, whereas real with core. Calculations dependent parameters are presented effects imparted on by different loss mechanisms (in insulation, in windings core) discussed. simulations compared results measurements...

This paper presents investigations on the performance of 33 kV silicone rubber insulators characterized by different creepage lengths, which aimed to find out whether could permanently work when electrically stressed beyond recommended limits in polluted and clean tropical environments. The study was performed under natural field laboratory conditions. tested included eight types composite insulators, one type hybrid siliconeceramic insulator semi-conducting glazed porcelain insulator, while...

Some new methods, based on characterization of the dielectric response transformer insulation in time and frequency domains, have been pointed out by CIGRE as suitable to assess moisture content pressboard paper. Measuring devices available today market are quite robust field conditions; however there is a risk that undesired internal external factors might influence measurements. These influences can lead mistaken interpretation wetness. Operators should therefore be aware risks appearing...

This paper presents how the frequency response analysis (FRA) measurements on a transformer can be influenced by magnetization condition of core. Measurements were performed two transformers at different levels to show effects remanent in core due removal 3-supply, relaxation demagnetization and dc flux winding impedance. The most important observations that any sudden change excitation field (applying or removing current) yields slowly varying magnetic relaxation, which causes impedance...

Surface potential dynamics on corona charged surfaces of thick samples EPDM and silicone rubbers have been studied analyzed by examining the so called tdV/dt characteristics. This methodology allows for directly obtaining information about charge trap distributions in materials from measurements decay without a-priori knowledge parameters. More importantly, combination above mentioned conjunction with other material parameters may provide desired when analyzing surface behavior composite...

Surface charge decay on thick flat samples of HTV silicone rubbers charged by impulse corona is studied. In the experiments, surfaces materials exposed to were kept open ambient air whereas opposite in contact with a grounded copper plate and surface potential distributions measured using Kelvin type electrostatic probe. The developed procedure allowed for implementation three study cases when (i) neutralization pre-deposited charges free ions present was prevented occurred mainly due bulk...

This article presents the results from round-robin tests performed on epoxy composite materials. These show potential of these materials for use as electrical insulation in some specific applications. A small section addresses health and safety issues related to nanoparticles power engineering industry. We define nanocomposites epoxy-based containing exclusively nanosized filler particles. Epoxy microcomposites are defined microsized particles, micro+nano composites both

To reduce the risk imposed by use of defected composite insulators on operation power grids, this paper introduces a nondestructive ultrasonic phased array (UPA) technique that allows effectively test such insulators. The method offers great potential reducing inspection time as well allowing for analyzing components characterized complex geometry. UPA system utilizes an open-ended rectangular waveguide sensor, operating at frequency 2.5 MHz. is simple, safe and relatively inexpensive. In...

Surface charge decay on thick flat samples of high temperature vulcanized silicone rubber is studied prior and after ac dc corona pre-treatments. It found that the rate material exposed to becomes much higher sensitive moisture content in surrounding air. These features are associated with an increased surface conductivity formation a silica-like layer polymeric surface, both resulting from treatment. In contrast, characteristics be similar measured untreated samples.

This contribution reports on properties of low-density polyethylene-based composites filled with different amounts graphene nanoplatelets. The studied samples were prepared in the form films by means precoating technique and single screw melt-extrusion, which yields a highly ordered arrangement flakes results strong anisotropy morphology. performed tests gas permeability reveal drastic decrease this property increasing filler content. A clear correlation is found between free volume fraction...