Reliability‐Based Design of Transmission Lines

Abstract

The structural design of high voltage electric transmission lines in the U.S. is most often governed by the National Electrical Safety Code (NESC). A simple Load and Resistance Factor Design (LRFD) format is proposed as an alternative to the NESC. The important steps needed to produce a design according to either the NESC or the LRFD are discussed and compared. It is shown that, with the proposed numerical values for the LRFD strength and load factors, accurate levels of relative reliabilities among different transmission lines, or among different structures of the same line, or among different components of the same structure, are achieved. A computer program, DESCAL, was developed to evaluate the reliability of a transmission line component designed according to any criterion, and, in particular, to the NESC or LRFD criteria. Results of reliability calibrations conducted over a wide variety of components and structure types indicate that, unlinke the NESC, the LRFD produces reliability-consistent designs.