After the electrical power is been generated it is needed to
transfer the electrical energy for utilization. But the generated electrical energy can not be directly utilized at consumer level as the power generated is of very
high magnitude around
15 kV or
17.5kV in general . So we employ,
Transmission and Distribution system. In this post we will cover the basics of Transmission system.
Transmission System
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| Transmission line |
The transmission system is simply defined as the transfer/transportation of electrical power generated in generating station to substation over a long distance. "Transmission System" is a broad term which directly refers to "Transmission Line." The basic remains same that electrical energy is transported from one place to another. Although "transmission line" is precisely defined as, " the transfer of electrical energy from generating station to substation in bulk." Generated electricity is in the form of 3Ø supply which is step up in power substation. Then it is stepped down in distribution substation to utilization level.
Standard transmission voltages are:
400kV, 220kV, 132kV, 66kV, 33kV, 11kV.
Normal voltages of primary transmission are:
132kV, 220kV, 400kV.
Different transmission system:
- Overhead transmission system
- Underground cable system
Overhead transmission System:
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| Overhead Transmission line |
We can easily view this system around us. This system is mostly used transmission system. Its consist of a bare conductor supported by the supporting structure and insulator. The high voltage conductors are not covered with any type of insulation. The supporting structure maintain clearance between ground and conductor and the insulator provide insulation between conductor and supporting structure. As the transmission voltage level increases, the height of supporting structure has to be increased to provide more clearance between ground and conductor.
Underground cable transmission system:
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| Underground Transmission line |
Electrical power is also transmitted by underground cables but it is not widely used. In underground cable system one or two or more conductors are bunched together but are properly insulated from each other. Underground cables are provided with lead sheet and armouring, this helps to prevent the cable from moisture and mechanical damage. The thickness of insulation among the conductors and between conductors and earth is increased if the voltage of transmission system increases.
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