This Green Book provides the design engineer with an understanding of the electrical parameters and methods required in designing compact AC and DC lines.  Compact AC and DC lines are becoming increasingly necessary due to the limitation of right of way access and the need to upgrade power transfer in existing, narrower line corridors. Another requirement for compact AC lines is the lower impedance permitting increased power flow. For DC power lines, increased power flow can only be realised by increasing the current through the conductors and/or increasing line voltage. In AC it can also be achieved by bundle expansion and phase compaction due to the variation of impedance. The effect of compaction on AC and DC lines is not identical as with the constraints. The Green Book covers the theory relating to the constraints such as corona, audible noise, insulation coordination, electric and magnetic fields and others for both AC and DC lines. In addition to the theory, the Green Book includes actual calculations of electric parameters for different pole (DC) and phase (AC) configurations. Standards applied by various countries are tabulated for easy comparison of practices internationally. Case studies on line compaction designs for both AC and DC are described with relation to pole compaction, pole rearrangement and phase configuration. Voltage upgrading is also treated in this book, and some case studies for both AC and DC are considered.