Suggestion: Consult Reference
1. Fink D. G., Beaty H. W., "Standard Handbook for Electrical Engineers," 14th Edition, McGraw-Hill, 2000, page 14-105 Paragraph "Recent Technology Options."
Excerpt: "The basic premise of compact transmission line design is application of design principles developed for EHV to redesign lines for lower voltages with smaller spacings."
Try Transmission Line Reference Book, 115-138 kV compact line design. Other transmission line reference books are also available for 345 kV and above as well as HVDC to 600 kV. These are EPRI books and are based on research they have done.