kV DC Voltage Research Articles

Second Harmonic Generation from Surface Crystallized Li2O–Ta2O5–SiO2 Glass

Preferential c-axis orientation of LiTaO3 was observed in surface crystallized 35Li2O·30Ta2O5·35SiO2 glass. Second harmonic generation (SHG) was observed in surface crystallized glass poled at room temperature for 24 h under a 0.7 kV dc voltage, whereas it was not observed in an unpoled sample. The SHG observed in this study was attributed to residual polarization in LiTaO3. The d33 value of the poled sample was estimated as 0.13 pm/V which was 0.5% of the d33 value for LiTaO3 single crystal.

Determination of Components in Eye Lotion by Capillary Electrophoresis.

Capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC) with sodium dodecyl sulfate (SDS) as an anionic carrier were applied to the analysis of nine principal components of eye lotion. Simultaneous separation of these components except cyanocobalamin (VB12), which has the same migration time with that of electroosmotic flow, was achieved by CZE using a 72 cm×50 μm i.d. fused silica capillary tube filled with 20 mM borate buffer (pH 10) at 25 kV DC voltage with UV detection at 200 nm. Under these conditions, the peak of chondroitin sulfate (CS) was overlapped with that of aspartic acid in case the latter was contained in the sample as a co-existing component. However, when pH was decreased to 9, CS was separated from other components and also from aspartic acid, and gave a more shapely peak. VB12 could be separated from other components by MEKC with 20 mM borate buffer (pH 10) containing 40 mM SDS. The applicability to the determination of nine principal components of eye lotion is demonstrated.

Diamond growth on carbon-implanted silicon

Diamond has been deposited on a silicon surface modified by low-energy carbon ion implantation. Carbon ions, which were excited by an RF discharge of methane diluted with hydrogen gas and were accelerated by 3 kV DC voltage, were implanted into silicon substrates with a dose of 3 × 10 16 ions/cm 2. The diamond particles grown on carbon-implanted silicon substrates using a conventional microwave plasma chemical vapor deposition system were single crystals with well defined facets. It was found that the nucreation density on this modified-surface was 5.4 times larger than that on a mirror polished silicon surface. These effects can be originated from microscopic diamonds formed in the carbon-implanted layer during diamond deposition. The high quality diamond particles grew up to 20 μm, because microscopic diamonds act like single nuclei for diamond growth.

Influence of an electric charge during quench aging of a low-carbon steel

We report here the first investigation on the quench aging of a low-carbon steel under the influence of an electric charge produced by 6.7 kV dc voltage between the specimen and a parallel electrode separated by 5 mm. This arrangement produced the following effects: (a) retarded the aging kinetics and (b) reduced the peak hardness. Fitting the results to a thermally activated rate equation indicated that the activation energy was increased from 0.65 to 0.85 eV. TEM observations revealed significant changes in precipitate size, morphology, and distribution near the grain boundaries and in the grain interior. It is proposed that the existing electrical conditions enhanced the migration of quenched-in vacancies from the grain interior to the grain boundaries.

Determination of space charge distributions in polyethylene samples submitted to 120 kV DC voltage

The measurements of charge distribution evolutions in polyethylene samples subjected to an applied voltage of <or=120 kV are discussed. To apply significant voltage gradients to plates or cables having an insulator thicknesses ranging from 5 to 10 mm, the large applied voltage was necessary. The possibilities offered by this equipment are illustrated by results obtained with 6-mm-thick plates. A comparison of the behaviors of 2-mm-thick plates and 6 mm thick plates made of the same materials and submitted to the same field is presented. The results indicate that increasing the thickness of the insulator does not increase the charge densities which develop under the applied field and that the observed space charge is localized at the vicinity of the electrodes, in a region extending over 0.7 mm, in which the diffusion of impurities from the semiconducting electrodes is very important.<<ETX>>

Natural contamination test of insulators with DC voltage energization at inland areas

Results of tests for natural contamination of insulator strings in inland areas are discussed. Natural exposure tests with -280 kV DC voltage energization were carried out for 5 years. The following results were obtained: (1) The amount of contaminant on the bottom surface increased with the length of the exposure period, for the first year, at inland areas. Therefore, estimates of contamination severity should use data obtained for exposure periods of at least one year. (2) Insulators near the line and ground sides of a string collect more contaminant than the middle when DC voltage is applied. However, the effect of nonuniform contamination on DC withstand voltage is not as great as expected when ratios of the number of heavily contaminated insulators to that of insulator string are from 15% to 30%. (3) No significant effect of DC voltage energization on the ESDD of the middle part of insulator strings has been observed when the applied voltage is no higher than 280 kV DC. (4) A pollution severity map established for AC transmission lines can be used for the determination of design ESDD for HVDC transmission lines for inland areas without industrial contamination. (5) The maximum value of leakage current under natural conditions is less than 3 mA, and no flashover has been experienced during these 5 years for electrical stress from 90 to 120 kV/m. The application of these results to insulation design for HVDC transmission lines is discussed. >

Effects of DC Prestressing on Tree Initiation in Polyethylene with and without Needle-Shaped Void

The effects of dc prestressing on tree-initiation in polyethylene wit needle-shaped voids have been investigated so that a comparison between specimens with and without voids could be made. When the polarity of the pulse is the same as the dc voltage, the effect of dc prestressing is negligible on the 50%-tree-initiation voltage. On the other hand, the opposite polarity gives a significant effect. For the dc prestressing test with the opposite polarity, the effect of the dc prestressing disappears in 2000 s for the specimen with void, and 4000 s for the specimen without void, using -16 kV dc prestressing voltage. In positive dc prestressing tests, the effect of the dc prestressing disappears in 5000 s under 16 kV dc voltage for the specimen without void. For the specimen with void, however, the recovery time is only 100 s.

Natural Pollution Test of Insulators Energized with DC High Voltage

Various types of insulators have been energized with ±250 kV dc voltage and exposed to natural conditions by the seaside continuously. Salt deposit density and flashover phenomenon of these insulators have been investigated extensively for about two years. According to the results obtained so far, the influence of dc voltage application on the salt deposit density was not so notable as expected, while the effect of insulator types on the voltage withstand strength was greater than anticipated.