Utility experience in the past few years has shown the possibility to eliminate the impact of transmission lines on the community by implementing techniques such as compact lines. The major motivation for the implementation of compact lines is that by using conductors that are spaced closer together and supported by smaller and more attractive structures, overhead transmission lines will be less visually intrusive and more likely to be accepted by the public.
CEATI awarded project # T173700-33/112 to METSCO, to assess the current practices in compact line design and provide a state of the art guideline. This guide includes technical concerns surrounding compact line design such as electromagnetic interference (EMI), Audible Noise (AN), Radio and TV interference (RI and TVI), safety associated with live-line work and maintenance procedures, insulation coordination with regard to switching and lightning surges and electric field stresses. This report also deals with controlling the motion of phase conductors to minimize the risk of a flashover. The implementation of phase-to-phase spacers is thereby discussed as an option to reduce the overall conductor movement.
The overall life-cycle cost of typical compact line structures is compared with traditional design options. METSCO designed a utility survey, submitted to CEATI project monitors and Transmission Overhead Line Design & Extreme Event Mitigation (TODEM) interest group member utilities. The various responses gathered from the surveyed utilities are used to identify the pros/cons of the compact line application and the associated design challenges. This report also discusses the existing knowledge gaps in regards to compact line design. A critical review of the IEEE Std. 516-2009 and the IEC Std. 61472-2013 is performed with a focus on compact HV lines.
The final section of the report covers innovative maintenance techniques, as applicable to compact lines including modified live-line practices, the use of Portable Protective Gap (PPG), and helicopter-based live maintenance work.
Compact line, overhead line design, right of way (ROW), minimum approach distance (MAD) calculation, portable protective air gap (PPAG)