Development of steel tower considered harmony with surrounding scenery for 500 kV transmission line

Since transmission lines pass through urban districts, national parks or along trunk roads and so on, we have often been asked to assess the impact which steel tower make on landscape by residents. Therefore, we have adopted special towers aiming at landscape impact reduction (environment harmony steel tower (EHST)), making several improvements on shape and color since around 1970. It varies with tower types however, the cost of EHST is 2 to 5 times higher than that of truss steel tower, which is normally used. It is the reduction of investment amount for reinforcement of facilities that all Japanese electric power companies think the most important problem, and each electric power company have made effort to accomplish low cost as well as consideration to environment simultaneously. Diverse preferences for EHSTs make it difficult to select appropriate tower for the sight. Therefore, TEPCO examines the possibility of introducing new EHST selecting method, that is, making local residents choose a tower among several candidate low cost EHSTs. In this paper, we introduce examination results of four kinds of low cost EHSTs for adoption to 500 kV overhead transmission line (simple truss type, rigid frame (H steel) type, triangular tie-rod type, octagonal truss type). The costs of these low costs EHSTs are all less than 1.2 times higher than those of normally used truss steel towers.