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.
Application of portable protective gaps for live work on compact 550 kV transmission lines
This paper presents result of research on the application of a portable protective gap (PPG) to live work on a compact 550 kV steel lattice tower. The objective of the research was to provide experimental evidence which confirms the needed coordination of the PPG sparkover characteristics with the sparkover characteristics of the worksite on the compact tower during live work. Sparkover characteristics of the worksite are strongly affected by the presence of the worker, the live working tools, and damaged insulators.
Switching Surge Sparkover Characteristics of Air Gaps and Insulator Strings Under Nonstandard Conditions
Sparkover characteristics of rod-rod gaps and insulator string by switching surge are presented under the following conditions: 1) With simultaneous application of switching surge voltages to both electrodes of a rod-rod gap. 2) With application of a switching surge voltage of the upper electrode in synchronizing to the peak of 50-cycle voltage which is continuously applied to the lower rod. 3) With surfaces of post insulator stacks and suspension insulator strings covered with snow or ice. 4) With surfaces of suspension insulator strings contaminated by salt.