Why is electrical energy transmitted at high voltage over long distances instead of low voltage?
Transmitting electrical energy at high voltage is important for reducing power losses in the transmission system.
When energy is generated in power plants (thermal, hydro, nuclear, renewable, etc.), it is immediately stepped up to extremely high voltages such as 110 kV, 230 kV, 400 kV (or) even 765 kV in step-up substations before being delivered to transmission lines.
The reasoning is based on a basic principle:
Power (P) = Voltage (V) × Current (I)
The current drops as the voltage increases for the same amount of power.
Since transmission losses depends upon current:
Losses (Ploss) = I² × R
where
R represents Line Resistance
Lower current results in significantly lower I²R thermal losses.
Eg: If the power is 100 MW, transmitting at 10 kV would need 10,000 A of current, resulting in significant losses and heat.
However, at 230 kV, the current required is just 435 A, significantly lowering line losses and conductor size.
This principle enables us to:
Large amounts of power can be transported over hundreds of kilometers in an efficient manner.
Maintain an inexpensive size for transmission lines.
Improve the grid’s reliability.
When power reaches consumption regions (cities, businesses, households), distribution substations scale it down to safer usable levels
(33 kV → 11 kV → 415 V → 230 V).
Engineers and technicians in substations, control centers & transmission networks ensure the electrical supply is safe, continuous, and efficient.
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