Experimental study on dynamic response characteristics of isolated-span transmission lines after ice-shedding

The dynamic response characteristics,including maximum jump height and unbalanced tension,of isolated-span transmission lines after ice-shedding are investigated by means of experiments.A reduced-scale modelling method for ice-shedding from conductor lines is presented and verified with numerical simulations and full-scale test results in the literature.A parameter study on dynamic responses of isolated-span conductors under three ice-shedding scenarios,including whole span ice-shedding,partial ice-shedding and unzipping ice-shedding,is carried out by means of reduced-scale modelling tests.The effects of these parameters on the maximum jump height at typical positions and unbalanced tension in the tension tower are obtained.It is observed that the partial iceshedding scenario may be the worst situation for electrical insulation clearance rather than the whole span ice-shedding scenario.Moreover,the position of maximum jump height along the span of isolated-span transmission lines after ice-shedding could be at around 2/5 of span length,which is different from the conventional opinion that the position is at the midpoint.The results may provide a foundation for the defining of the insulation clearance for an isolated-span transmission line and the structure design of tension tower arms in an iced zone.

Self-cleaning of superhydrophobic nanostructured surfaces at low humidity enhanced by vertical electric field

Self-cleaning is the key factor that makes superhydrophobic nanostructured materials have wide applications.The self-cleaning effect,however,strongly depends on formations and movement of water droplets on superhydrophobic nanostructured surfaces,which is greatly restricted at low humidity(<7.6 g·kg^(-1)).Therefore,we propose a self-cleaning method at low humidity in which the pollution is electro-aggregated and driven in the electric field to achieve the aggregation and cleaning large areas.The cleaning efficiency of this method is much higher than that of water droplet roll-off,and will not produce"pollution bands".A simplified numerical model describing pollution movements is presented.Simulation results are consistent with experimental results.The proposed method realizes the self-cleaning of superhydrophobic nanostructured surfaces above dew point curve for the first time,which extends applications of superhydrophobic nanostructured materials in low humidity,and is expected to solve self-cleaning problems of outdoor objects in low humidity areas(<5.0 g·kg^(-1)).

Pollution morphology characteristics on a superhydrophobic surface and its pollution flashover voltage in DC electric field

To solve the pollution problem of insulators on ultra-high voltage DC transmission lines,superhydrophobic coatings were presented and their pollution deposit morphology and pollution flashover voltage in electric field were studied by an artificial pollution deposit system.The experimental results show that the pollution on the surface of super-hydrophobic coating is distributed in clusters,which inhibits the chain distribution on the surface of silicone rubber and improves the pollution flashover voltage.Secondly,the competition mechanism of the pollution flashover on the superhydrophobic coating surface was found.This competition mechanism can lead to the failure of the insulation performance of the superhydrophobic coating in severely polluted environments.Finally,a pollution flashover model of superhydrophobic coating is proposed to explain the competition mechanism,which is affected by pollution and the discrete droplets.The conclusions of this study can provide an experimental and theoretical basis for the application of the superhydrophobic coating in the field of UHV DC external insulation.

Universal precursors dispersed in Vaseline-octadecene gel for nanocrystal synthesis

A great variety of high-quality inorganic nanocrystals are synthesized solely in hydrocarbon solvents in both academic and industrial settings on a daily basis,which is largely complicated by lack of simple precursors containing inorganic element(s)yet soluble in the reaction solvents at ambient temperatures.Here,we introduce a new strategy for preparing the precursors,namely inorganic(or element-containing organic)molecules dispersed in hydrocarbon(Vaseline-octadecene)gel.This strategy not only greatly expands spectra of potential precursors and their concentration range,but also simplifies synthetic system,enables automated large-scale synthesis,and minimizes environmental concerns.

Thermal shock resistance enhancement by improved interfacial bonding for carbon/aluminium composites

Carbon/aluminium(C/Al)composites have the advantages of low density and high electrical conductivity,which have potential applications in aerospace,rail transportation and other fields.However,the unstable bonding of the C/Al interface and significant thermal expansion differences have resulted in risks of the composites'failure once suffering from severe thermal shock.In this work,the C/Al composites were prepared by the pressure impregnation method,and silicon(Si)was added to overcome the problems of C/Al non-wettability and thermal expansion differences.The effects of mass fractions of doped silicon on the mechanical properties,electrical conductivity and thermal shock resistance of C/Al composites were also examined.Results show that the formed SiC interlayer has effectively enhanced the interfacial bonding and reduced the differences in the thermal expansion coefficient of each component.As a result,the thermal shock resistance of the composites has been remarkably improved,and the flexural strength could remain 90%of the original level after the thermal shock test,compared with 50%of that without Si doping.