4. Phase/Pole Configuration, Conductor and Hardware

This section describes the different phase or pole configurations that can be used for compact lines. They need to be divided into Right of Way (ROW) reduction and Surge impedance Loading (SIL) improvement (only for AC lines). For ROW reduction examples such as vertical configuration, compact delta with composite post cross arms, etc., can be described. For SIL improvement, increased bundle diameter, asymmetrical shaped bundles in delta or inverse delta with composite cross arms are proposed for study. The DC overhead power lines do not improve the power flow by modifying pole spacing or the bundle diameters, unlike in AC overhead power lines, where these parameters affect the surge impedance loading of the line. Therefore, in DC compact lines, the different pole configurations pursue a reduction of the Right of Way, a reduction of the visual impact and/or an optimisation of the corona-related effects (electric field, ion current, audible noise, etc.). The limits to these effects may often be the governing aspects of the design of compact DC lines. The overall design of a compact line in general considers this configuration as a primary concern, which is complemented with the conductor selection process, tower and foundation designs and hardware solutions. All these aspects are included in this section, which also gathers a general discussion on galloping, as it may be one of the major issues in compact lines due to the reduced clearances between phases or pole conductors and/or between them and the groundwires.