Embodiments generally relate to long-distance, 3-phase, AC electricity transmission structures. In one embodiment, the structure comprises an array of beams, the array comprising a sub-array of 3N active beams, wherein N is an integer, one passive beam on the right side of the sub-array of active beams; and one passive beam on the left side of the sub-array of active beams. The centers of the cross-section of each of the active and passive beams lie in a single plane. In another embodiment, the structure comprises an array of 3N metal active beams, wherein N is an integer; and a tunnel of rectangular cross-section with either 90 degree or rounded corners. The array of beams is mounted within the tunnel, and the two side walls of the tunnel are lined with a highly conductive metal having a thickness similar to the thickness of metal used in the active beams.