Examination of clearances during high voltage live-line working

High voltage live-line maintenance (LLM) became a decisive working method in Hungary in the 1960s. Most of the LLM techniques and equipment - which are still in operation nowadays - were developed by Dr. Béla Csikós, who was one of the pioneers of high voltage live-line work. In those days the live maintainability of the power lines was a significant aspect during the design of towers and insulator strings. Contrarily, structures change year-by-year, especially regarding the insulators. Therefore, live working methods also shall be developed. Nowadays, new types of tower structures and insulator strings are used with reduced distances, which also means reduced clearance between the different potentials in the arrangement. During barehand live working method, the lineman has to keep the adequate distances from different potentials of power lines. Moreover, there is no uniform standard and international practice for the regulation of safety clearances. New type of mounting chair made of non-conductive material is suitable for approaching the insulator strings and their fittings safely, as the air gap between the conductive parts does not shorten. The aim of this paper is to investigate the usability of non-conductive mounting chair and the regulation of phase-to-ground clearances during insulator replacement technology, in case of several tower types and insulator types used in the Hungarian transmission grid. Another purpose of this article is to examine the possibility of reducing minimal approach distances, such as by the application of portable protective air gap (PPAG).