Tension is the force applied to the conductor to keep it between the two towers. The force needed to break the conductor is called ultimate tensile strength.
The presence of electrical resistance in the wire causes all the energy provided by the energy supplier not to reach the receiver and some of the energy is lost as heat. Energy losses can be reduced by increasing the number of circuits, bundling transmission lines and using conductors with lower resistance (higher cross section).
Transmission lines: 230 kV and 400 kV
Sub-distribution lines: 63 kV and 132 kV
Distribution lines: 20 V and 400 V.