Converter transformers are the core device in ultrahigh voltage direct current(UHVDC)transmission systems,and the oil-paper insulation at its rectifying valve side deals with the composite AC-DC voltage.A detailed inv...Converter transformers are the core device in ultrahigh voltage direct current(UHVDC)transmission systems,and the oil-paper insulation at its rectifying valve side deals with the composite AC-DC voltage.A detailed investigation of the partial discharge(PD)mechanism in the oil-paper insulation under the composite AC-DC voltage is,therefore,very important.The oilpaper insulated needle plate electrode simulation model for the electric field and charge distribution can be established using hydrodynamic drift-diffusion theory and bipolar charge carrier theory,and the simulation results can reflect the morphological changes of PD.The development characteristics of PD under composite AC-DC voltage are researched.In addition,the effects of simulation time,the AC-DC component proportion,and model parameters on PD are also explored.Results indicate that differences in applied voltage,interface charge,and geometry structure can cause changes in the electric field strength,which consequently influences the PD process in the simulation model.Oil-immersed paperboard is a type of liquid-immersed dielectric(LID).When the LID is arranged in perpendicular,only the positive streamers have narrow channels oriented toward the LID.When the LID is arranged in parallel,the PDs are in the form of creeping discharges and the negative streamers are more dispersed.The development characteristics of PD and its influencing factors reported here may provide theoretical and simulation support to explain the physical mechanism of PD at the rectifying valve side of the converter transformer.展开更多
Raman spectra and surface-enhanced Raman scattering （SERS） spectra of filter paper and silica gel plate are ob- tained at 785-nm excitation wavelength. The results show that filter paper has thirteen Raman lines in ...Raman spectra and surface-enhanced Raman scattering （SERS） spectra of filter paper and silica gel plate are ob- tained at 785-nm excitation wavelength. The results show that filter paper has thirteen Raman lines in 800 - 1 500 cm 1 and silica gel plate has eight lines in the region of 400 - 1 200 cm-I. The frequencies and Raman active modes are assigned. By comparing their Raman spectra and SERS spectra, we find that the silver colloid could repress the Raman intensities of filter paper and silica gel plate, and reduce their effects on the combination of thin-layer chromatographic （TLC） and SERS. Ac- cording to SERS spectra, the bands at 997 cm 1,1 094 cm I ,1 118 cm-1 ,1 336 cm-1 and 1 378 cm-1 for filter paper and the peak of v l [ SO4] symmetric stretching vibration （--1 017 cm-1 ） for silica gel plate also have high intensities, and those lines should be paid enough attention in TLC-SERS.展开更多
基金This work was supported in part by the Science and Technology Project of State Grid Corporation of China(No.52060020002P).
文摘Converter transformers are the core device in ultrahigh voltage direct current(UHVDC)transmission systems,and the oil-paper insulation at its rectifying valve side deals with the composite AC-DC voltage.A detailed investigation of the partial discharge(PD)mechanism in the oil-paper insulation under the composite AC-DC voltage is,therefore,very important.The oilpaper insulated needle plate electrode simulation model for the electric field and charge distribution can be established using hydrodynamic drift-diffusion theory and bipolar charge carrier theory,and the simulation results can reflect the morphological changes of PD.The development characteristics of PD under composite AC-DC voltage are researched.In addition,the effects of simulation time,the AC-DC component proportion,and model parameters on PD are also explored.Results indicate that differences in applied voltage,interface charge,and geometry structure can cause changes in the electric field strength,which consequently influences the PD process in the simulation model.Oil-immersed paperboard is a type of liquid-immersed dielectric(LID).When the LID is arranged in perpendicular,only the positive streamers have narrow channels oriented toward the LID.When the LID is arranged in parallel,the PDs are in the form of creeping discharges and the negative streamers are more dispersed.The development characteristics of PD and its influencing factors reported here may provide theoretical and simulation support to explain the physical mechanism of PD at the rectifying valve side of the converter transformer.
基金Programs for Science and Technology Development of Shandong,China(No.2010GSF10285)
文摘Raman spectra and surface-enhanced Raman scattering （SERS） spectra of filter paper and silica gel plate are ob- tained at 785-nm excitation wavelength. The results show that filter paper has thirteen Raman lines in 800 - 1 500 cm 1 and silica gel plate has eight lines in the region of 400 - 1 200 cm-I. The frequencies and Raman active modes are assigned. By comparing their Raman spectra and SERS spectra, we find that the silver colloid could repress the Raman intensities of filter paper and silica gel plate, and reduce their effects on the combination of thin-layer chromatographic （TLC） and SERS. Ac- cording to SERS spectra, the bands at 997 cm 1,1 094 cm I ,1 118 cm-1 ,1 336 cm-1 and 1 378 cm-1 for filter paper and the peak of v l [ SO4] symmetric stretching vibration （--1 017 cm-1 ） for silica gel plate also have high intensities, and those lines should be paid enough attention in TLC-SERS.
