Transmission Lines
The transmission lines are part of the system that gets electricity from the power stations to homes and it is made up of aluminum because it is more abundant, cheaper and less dense than copper.
It carries electromagnetic energy from one point to another point and it consists of two conductors that are used to transmit electromagnetic waves over a long distance between transmitter and receiver are called transmission lines.
There are both AC (Alternating Current) and DC (Direct Current) transmission lines.
The AC transmission lines are used to transmits alternating current over a long distance using three conductors.
DC transmission lines are uses two conductors to transmit direct current over a long distance.
Electrical current can be carried by either overhead or underground lines.
The main characteristics that distinguish transmission lines from distribution lines are that they are operated at relatively high voltages, they transmit large quantities of power and they transmit the power over large distances.
The types of Transmission Lines
Overhead AC Transmission Lines
They carry 3-phase AC current.
The voltages vary according to the particular grid system they belong to.
Transmission voltages vary from 69 kv up to 765 kv.
The DC voltage transmission tower has lines in pairs rather than in threes (for 3-phase current) as in AC voltage lines.
One line is the positive current line and the other is the negative current line.
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| 3 Phase AC Current |
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| Two Line DC Current |
Subtransmission lines carry voltages reduced from the major transmission line system.
Typically, 34.5 kv to 69 kv, this power is sent to regional distribution substations.
Sometimes the subtransmission voltage is tapped along the way for use in industrial or large commercial operations.
Some utilities categorize these as transmission lines.
Underground transmission lines are more common in populated areas.
They may be buried with no protection, or placed in conduit, trenches, or tunnels.
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| Underground Cable |
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| Under Cable In Cable Tray |
Applications
The applications of transmission line are
Power transmission line
Telephone lines
Printed circuit board
Cables
Connectors (PCI, USB)
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