National Environmental Standards for Electricity Transmission Activities: technical (2 of 9)
The technical pages provide background and explanations of:
Transmission lines
Existing lines
The following diagram identifies a range of transmission line types and components used in the existing transmission network.
The National Grid is made up of a range of transmission line designs: among other aspects these are differentiated by their voltage (see next page), the number of conductor sets or circuits carried, and whether they are supported by steel lattice towers or poles.
All alternating current (AC) transmission systems carry circuits comprising three conductors or wires or sets of conductors; each set is known as a phase. The three phases are named red, yellow and blue. Some transmission lines carry only a single three-phase circuit (three sets of wires), whereas others carry two three-phase circuits (six sets of wires).
The figure on this page identifies some of the components that comprise transmission lines.
Last updated: 18 January 2010
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