Power systems
An electric power system consists of 3 principle sections.
- Power stations: electricity is generated
- Transmission: voltage is stepped up to high voltage
- Distribution: voltage is stepped down to medium voltage for distribution over a relatively small region
Variable load
Load on a power station changes with to uncertain demands of consumers. This is called the variable load.
Load vs time curve is called the load curve. Area under this curve is the total energy requirement.
Power grid
Nation-wide, massive, geographically distributed system for electrical power supply network.
Sri Lankan Scenario
There are 2 major electric utilities in Sri Lanka: CEB and LECO.
Voltage Levels
- Generation voltage
- High voltage
or - Medium voltage
or - Nominal voltage
- Nominal line-to-line
Power sources
Hydro-power is the most used source of energy for electricity.
Why high voltage transmission?
Reduction of power losses
Power losses in transmission lines are called "
Power generation in the generator is constant. So voltage is increased to reduce the current.
Reduce voltage drop
Voltage drop in the transmission lines is proportional to the current flowing through it.
Reduction of power transmission cost
To carry higher currents, the transmission lines must have higher cross sectional area. Reduced current means smaller transmission lines are enough. Which leads to reduced cost.