Transmission lines are three-phase systems. There are three line conductors in a three-phase system. However, to reduce electric stress at higher voltages, these lines are frequently made up of 'bundled' conductors -so each line might have two, three, or four separate conductors. In addition, transmission towers usually carry separate circuits -i.e. separate three-phase circuits on opposite sides of each tower.
So, in the UK for example, a typical 400-kV transmission line will consist of two, separate, three-phase circuits suspended on each side of each tower, with each line consisting of four bundled conductors. That's 24 conductors.
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A basic transmission line uses two parallel wires, which can be coaxial as in coaxial cable with an inner conductor and an outer sheath.
3-phase transmission lines use 3 wires, or 4 wires for low-voltage supply. Power transmission lines usually carry two 3-wire circuits, so there are 6 wires. On the highest-voltage lines multiple conductor are used with up to 4 wires bundled together in parallel with spacers.
Ground wireAnswerIt's a (lightning) protection wire, designed to protect the line conductors from lightning strikes.
Transmission lines do not use a neutral conductor, so your question isn't actually relevant. Neutral wires are only necessary where imbalance may be large, and under some conditions current may be flowing in the neutral. Under these conditions a low impedance path (the neutral wire) is more desireable than a high impedance path (the ground). In many overhead transmission lines, a fourth or fifth wire are placed above the current carrying conductors; these are shield wires (not neutral wires) and are used to minimize outages on the line due to lightning (the lightning will strike these instead of the phase wires, these will flash over to the structures and the energy will be shorted to ground without the line having to be removed from service). When you're dealing with things that cost ~$100,000 - 2M/mile, it may be worth the added expense of a shield wire to keep it in service as much as possible.
A lossless transmission line is when no energy is lost during transmission of energy from a particular source to destination by a certain material, ie. copper wire. In other words, this material that transmits energy, absorbs none of the energy transmitted. No energy is lost to the material during transfer of energy. It is like saying it is an absolutely perfect conductor having no resistance.
Hill's Hoist is a type of clothes line used for drying clothes. It is an arrangement of wire or rope that rotates about a center rather than being a single long straight wire or rope. There are many variations in the design.
There are essentially 2 types of connections for a 3 phase AC transmission lines Star and Delta , Star is a 4 wire connection with each phase supplying potential with respect to a common ground wire , while delta is 3 wire connection with any single phase at one given time acting as a ground , for transmission reducing one wire makes a lot of cost difference hence it is favored