How do single-circuit lines compare with double-circuit overhead lines?
14.1 For normal 3-phase lines, the single-circuit lines require only three conductors and therefore less space than double-circuit lines with six conductors. Often the single-circuit lines have the conductors spaced almost horizontally, so they occupy a similar width to the double-circuit lines which have three vertically spaced conductors down each side. Therefore the single-circuit lines are considerably shorter than their double-circuit counterpart, typically for 400 kV lines around 25-35 metres compared with 45-60 metres. Since their lowest conductors are suspended at about the same height, the span lengths (pylon to pylon) tend to be similar for both single- and double-circuit lines, at about a third of a kilometre. 14.2 There is a marked difference in the EMFs. Those from a single-circuit line will spread much further to the side, away from the line, compared with those from a phase-transposed double-circuit line carrying the same total load. This is because of a partial cancelli
