Increase in ground clearance on old Transmission Lines located in industrial and residential areas

The old transmission lines located in industrial and residential districts usually have an unsufficiently short height clearance. This problem could be caused by different reasons like "the maximum creepage phenomenon of conductors", " the effect of air pollution and conductor corrosion in reducing the mechanical and electrical performance of conductors", "electrical overload of these lines caused by electrical consumption load growth under special and Urgent conditions and other different reasons in this regard. But the main factor is the aging of these lines i.e. the age of these lines from the date of stringing ahead is somewhat more than 15 years. The route of such lines at the time of stringing has been through suburb of cities or outside of residential and industrial areas or through rural areas and the minimum clearance which has been taken into account in design of these lines has been that of normal cultivated grounds with a light degree of vehicle traffic down under the line While as the time passed by, those rural areas gradually changed into urban and heavily industrialized regins so that a considerable part of these lines are inside the urban regions at the time being. So, considering some activities like road construction and creating green spaces and tree planting and erection of residential units and industrial installations near and / or around the "right of way" of these lines and regarding the heavy motor vehicle traffic around and under these lines, now the height clearance of these lines seems to be not sufficient and from the safety and protection point of view they may bring some obstacles for these areas. We have in this paper the honor of presenting the result of the years of investigations and experiences of Isfahan Regional Electric Company in increasing the height clearance of these old double circuit 63 K.V. transmission lines which are now located in urban rigions of the city of Isfahan.