架空送電線用高張力スチール芯材

Using a steel reinforcement core is the most cost-effective, long-term choice for your conductors. Though initial costs might be lower if you choose not to reinforce your conductor with a steel core, you increase the risk of premature failure and related costs, annihilating any initial cost-savings. 

Bekaert offers three types of high tensile steel cores: Ultra, Mega and Giga. The wires in each strand feature outstanding tensile strength, allowing the strand to move with the environment without creating excessive sag. The combination of these features results in conductors with a much higher capacity and which allow a more efficient distribution of energy.
Recently the International Electrotechnical Commission released the new IEC 63248 Norm which covers also high tensile strength Mega and Giga steel cores ( S7A, S8A) for overhead power lines. The advantages of the high tensile steel cores are described in CIGRE paper which you can find below in downloads.

Adding a steel core increases the breaking strength of an aluminum conductor by a factor of 2 to 3. Conductors with a steel core are more resistant to thermal sag and sag caused by various load conditions such as heavy winds and ice loading. Moreover, the cores reduce horizontal blowout distances and, as a consequence, the probability of horizontal clearance violations.