Calculation of Ninimum Safety Distances for Live-Line Mintenance - A Statistical Mehod Applied to 765 kV AC Itaipu Lines
This paper presents a statistical method to calculate the miniumm safety distance for live-line maintenance. The method takes into account the complexity of the tower gap configuration and the presence of the lineman working at the line potential. It includes the inherent dispersion of the dieletric characteristics of the air gaps such as the probability of flashover and the tirnes-to-flashover. Laboratory tests were also performed to corroborate the results of the study, checking not only the performance of the various live-line tools but also the effectiveness of the by-passing insulators protective device and the occurrence of broken insulators in the string.
Defective insulators in live working on a 550 kV compact steel lattice tower
Research was conducted to determine the minimum number of healthy insulator units needed to ensure worker safety in live working on a compact 550 kV steel lattice tower. A large variety of worksite conditions was investigated. Test results confirm the conservative nature of the CIGRE formula for defective insulator units, and modifications to the formula are suggested, The recommended number of healthy units is 12 in a string of 24 units for the case of live work on a compact 550 kV tower, when the portable protective gap (PPG) is used. Adjustment for altitude should be made above 900 m (3000 ft.).
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.