Modeling of Partial Discharges from a Spherical Cavity within a Dielectric Material under Variable Frequency Electric Fields
Partial discharge (PD) is a discharge event that does not bridge the electrodes within an electrical insulation system under high voltage stress. In high voltage components, the measurement of partial discharge is used in the performance assessment of an insulation system. Through modeling the discharge process a better understanding of the phenomena may be attained. Previous studies have considered the modeling of PD activity from a cylindrical cavity. However, this is a limited approach as the most common types of cavities found in the insulation materials are either spherical or ellipsoidal. This paper describes the development of a model for a spherical cavity within a homogeneous dielectric. The model developed has been used to study the influence of the applied frequency on partial discharge activity and obtained results are presented.
Simplified hybrid PD model in voids: Pattern validation
The purpose of the present work is to show the validation of a new model to simulate the physical phenomenon of partial discharge (PD) produced in air voids inside insulating epoxy resin. The model has been developed on the basis of a new approach that combines the known circuit model of three capacitors with a model used to describe the behavior of the ionized channel inside of the inclusion during the discharge phenomenon, short-circuiting the capacity that represents the void. The approach is based on time-variable conductance of the void, subjected to multistress conditions: voltage, temperature and pressure. The new approach has been developed from a time variable conductivity model used for the study of the discharge with dielectric barrier (DBD). The different parameters which influence the discharge phenomenon in the void are taken into account through an approach in which a lumped circuit is used to simulate the effects of global PD asset. The results of the multiple simulations have been compared with experimental and simulated behaviors found in the literature on the subject.
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.