Dielectrometry Measurements of Moisture Diffusion and Temperature Dynamics in Oil Impregnated Paper Insulated Electric Power Cables
Paper insulated lead covered (PILC) cables provide the backbone of underground power distribution in the United States and other parts of the world. Efficient replacement of aged PILC is a looming challenge for the utility industry. Interdigital dielectrometry sensors that measure the dielectric properties of PILC cable are presented. Such sensors may be used to perform low cost health assessment of excavated cable samples. An overview of the theoretical groundwork is presented along with steady state and transient experimental results.
Dielectrometry measurements of moisture dynamics in oil-impregnated pressboard
The dielectric spectrum of pressboard, (i.e. its complex permittivity as a function of frequency), is related to its moisture content and to its temperature. Consequently it is possible to use dielectrometry measurements to measure a pressboard sample's moisture content. The complex permittivity of pressboard is measured in two different ways. The first method places the sample between two parallel metal plates, in effect creating a lossy lumped capacitor, whose complex impedance can easily be measured. The complex permittivity thus calculated is effectively averaged across the sample's bulk. The other method involves interdigitated electrodes, applied only to one surface of the sample. Since the electric field's depth of penetration is dependent on the spatial wavelength of the electrodes, different sensors can obtain information from different depths in the material, making it possible to measure spatial distributions of the dielectric properties. This can allow the study of the diffusion of water in pressboard.<<ETX>>
DESIGN CONSIDERATION TO PPM KLYSTRONS FOR INDUSTRIAL LINAC
Toshiba has been developing the C-band and X-band Periodic Permanent Magnet (PPM) focused klystron in collaboration with KEK and manufactured prototypes for the JLC project. [1] The PPM klystron has an advantage to enhance the total efficiency as a result of eliminating the electric power for the focusing magnet. From experience on the development the PPM focused klystrons for the JLC project, we plan to apply the PPM focused klystron to the medical and industrial linac. The periodic magnet focusing scheme has some technical difficulties such as stop band voltage. To design the PPM klystron for the medical and industrial linac, it is necessary to give heed to electron beam instability; so that the tube parameters of the PPM focused klystrons have some constraints. The size of the accelerator system is substantially reduced if a PPM focused klystron is used. The majority of medical and industrial linacs use frequencies of S-band range. We discuss the availability of the S-band PPM focused klystron in this paper.