We review the results of electrical conduction and breakdown research reported mainly after 1980 in Japan, comment on present situation future prospect work this field. Effects introduction polar groups into polymers electric strength F/sub b/ are summarized. Influences copolymerization modification morphology chemical structure polyethylene also reviewed. Finally, we show currently used experimental techniques for direct observation space charge, prebreakdown current localized heat...

Summary Geologic carbon dioxide (CO2) sequestration has received significant attention from the scientific community as a response to global warming due greenhouse gas emissions. Effective monitoring of CO2 plume is critical storage safety throughout life cycle geologic project. Although simulation-based techniques such history matching can be used for predicting evolution underground saturation, computational cost high-fidelity simulations prohibitive. Recent development in data-driven...

Summary Routine well-wise injection/production data contain significant information that can be used for closed-loop reservoir management and rapid field decision-making. Traditional physics-based numerical simulation computationally prohibitive short-term decision cycles, it requires a detailed geologic model. Reduced physics models provide an efficient simulator-free workflow but often have limited range of applicability. Pure machine learning lack physical interpretability predictive...

Abstract Ensemble-based methods such as ensemble smoother with multiple data assimilation (ESMDA) have been widely used for subsurface history matching of spatial parameters (e.g., the permeability field). However, when system is only parameterized a dozen parameters, applying ensemble-based can lead to collapse and spurious updates even localization. In this work, improvements were proposed address these problems. practical matching, often characterized by intuitive interpretation...

Local Joule heating in polyethylene films was detected at room temperature before dielectric breakdown under DC field. When a high-temperature point appeared film, the conduction current increased with time. The final occurred of highest temperature. This concurrence and suggests that thermal process takes part electrical there are weak points leading to film where density is above average. Almost same results were observed for ethylene-vinyl acetate copolymer films, although local lower...

This paper summarizes the result of questionnaire on current status non-ceramic (composite) insulators in world conducted by Non-ceramic Insulators Technical Committee, Japan. Current use status, reasons for use, maintenance, failure occurrence and research activity 16 responding utilities are described. About 80% answered that they would actively increase future. It is anticipated market these will keep expanding.

A nanocomposite material, composed of nano-sized MgO-filler added to a low-density polyethylene (LDPE), was subjected electrical property investigations under DC voltage application. The volume resistivity LDPE, 40-80 kV/mm field at 90 /spl deg/C, increases by the power 10 due addition only few percent nano-filler. amount space charge in LDPE high electric is reduced and ratio stress enhancement becomes less MgO-filler. breakdown strength increased adding Based on these results, mechanism...

A nano-composite material of magnesium oxide (MgO) added to a low-density polyethylene (LDPE) was subjected electrical tree breakdown investigation. The LDPE without nano-fillers lower in voltage than the with nano-fillers. increased by increase nano-filler concentrations LDPE. This result much coincided on inception which when concentration filler increased. It is considered that fillers would create such an obstruction bridging counter electrode. However, even had bridged electrode; not...

Epoxy resin is widely used as an insulation material in many electrical apparatuses because of its excellent and manufacture characteristics. It usually mixed with filler to improve mechanical thermal In order qualitatively clarify the effect fillers on treeing phenomena, tests were performed epoxy specimens different kinds fillers. The property interface also clarified by treatment silica using silane coupling. Although tree initiation voltage decreased introducing fillers, prevented growth...

In order to investigate transient space charge phenomena, it is essential that the profile be observed at a high repetition rate. We have developed new measurement system using pulsed electroacoustic (PEA) method, which can measure profiles every 10 /spl mu/s. It employs most recent digitising oscilloscope model and semiconductor switch. The effect of prestressing on impulse breakdown voltage low-density polyethylene sheet was investigated by system. Experimental results suggest positive...

Mechanical and electrical properties of ethylene propylene rubber (EPR) pieces were studied in comparison with polyethylene (PE) the cryogenic temperature region to examine possibility its use as solid insulating material superconducting cables. The mechanical EPR are preferable those PE mainly because low shrinkage. electric strength dielectric loss tangent comparable at liquid helium temperature. Based on encouraging results, an extruded EPR-insulated cable was fabricated 15-m length...

This paper deals with a water tree retardant characteristic of magnesium oxide (MgO) nano-filler addition to low-density polyethylene (LDPE) and cross-linked (XLPE). Water retardation both LDPE XLPE at 313 K was improved adding the MgO content more than 2 phr, while it almost same level less phr. From comparison result MgO/XLPE MgO/LDPE, superior that MgO/LDPE where shows no remarkable property. When is 5 however, retardations due became improvement nano-filler. As for influence temperature,...

A novel method for the detection of high-field AC conduction loss current containing harmonics in polymeric insulating materials is presented. The based on use unbalanced operation a current-comparator-type capacitance bridge and deconvolution technique signal processing. This was experimentally applied to diagnosis water trees CV power cables by detecting waveform with without tree degradation. distortion measured water-tree-degraded cable appeared be larger than that observed nondegraded...

We have proposed a new method for two-dimensional acoustic impedance imaging biological tissue that can per- form micro-scale observation without slicing the specimen. A was placed on plastic plate of 0.5 mm in thickness. An pulse with frequency range up to 100 MHz trans- mitted from rear side plate, beam being focused at boundary between and plate. The reflec- tion intensity interpreted into local target tissue. microscopy 200 x pixels, its field view 2 mm, obtained by mechani- cally...

This paper presents an attempt to derive the dielectric permittivity characteristics of polymer composite filled with metal oxide particle which has mesoporous structure. Experiments were carried out on epoxy composites alumina microparticles have structure (mesoporous-alumina/epoxy composites) different content. Measurement specific gravity mesoporous-alumina/epoxy indicated that porosity mesoporous-alumina in matrix was higher than nonporous-alumina particle. Furthermore, we evaluated...