RELIABILITY-BASED OPTIMIZATION OF TRANSMISSION-LINE TOWERS

Transmission line towers form the major part of a power grid and contribute a large percentage to the total cost of the transmission line network. The structural design of a transmission line tower is most often governed by IS:802-1977, IS:802 (draft)-1989 (Indian standard code for design of transmission line towers) and Indian electricity rules. There have been failures reported in transmission line towers, particularly in Andhra Pradesh, a southern state of India, due to cyclonic storms. Against this background of codal specifications not properly taking into account the uncertainty factors in loading and material properties, the need for reliability-based design is highlighted in the present paper. Four independent computer programs for component reliability, reliability analysis, optimization and automation of failure mode generation were developed. Not only were these programs independently developed and validated, they were all linked together. This has enabled not only the more economical design of typical towers but also ensured a particular level of chosen reliability for the towers. It has also been demonstrated that the program can be used for checking the existing towers for assessing the reliability levels available in them.