An electrical power system is a network comprises of different electrical components employed to use and transfer the electrical power. The electrical network that connecting the distribution transformers and the different loads in the residential areas is an example of the power system.
For larger regions, this power system is termed as the GRID.
The Grid can be broadly classified into three sections;
- Generation system
- Transmission system
- Distribution system
 |
Figure 1. HOW ELECTRICITY GETS TO YOU?
|
In the generating system, different power stations employing electricity generating sources like a dam, fuel, solar power, wind power etc. will be available.
- The transmission system is responsible for transmitting the so-called generated power through transmission lines. The step up transformers are provided to step up the generated voltage and reduce the line losses in transmission.
- The distribution system will be distributing the power from the transmission lines to the different consumers(loads). Different transformers are also provided in the distribution centers to step down the high transmitted voltage to the consumer rated voltage.
Thus the power grid transmits the extra high voltage generated in the power plants to the consumers. On the way of its transmission, power grid converts the extra high voltage to necessary levels. Finally, consumers deliver their appropriate voltage level.
Most of the transmission lines are overhead lines. Steel structured towers are used for supporting the conductors or transmission lines. Good insulators are used to prevent the conduction between the supporting towers and these transmission lines.
Underground cable transmission is also there for transmitting the voltage. But the cost of underground transmission is more expensive than high voltage overhead transmission. The cost will be more when burying the power cables with same capacity that of overhead power lines. The life-cycle cost is also high for the underground system.
Why are we using high voltage to transmit electrical power?
The generated voltage is usually stepped up to high levels for transmission. The following reasons would explain it in a better way.
- Higher the voltage level, lower will be the current. So the losses ("I squared R losses") will be less.
- Reduction in losses improves the overall efficiency of transmission.
- The size of conductors required for the high voltage transmission is less. As the voltage increases, the resistance also increases. And the resistance is inversely proportional to the area of the conductor.
Through the transmission lines, this high voltage first reaches the substations before reaching the homely consumers. In the substations, the high voltage will be stepped down to the distribution level voltage. Finally, at the service location, the voltage will again be stepped down to the service voltage.
