Ferranti effect – The effect due to which the receiving side gets slight higher voltage than the transmitted voltage.
It is also known as charging current effect.
We know, in normal condition when we transfer electricity from one station to another it looses a lot of power in the form of heat due to resistance of wire and skin effect. Voltage keeps on decreasing as we move towords receiving end. Due to this we receive a slight lower voltage on the receiver side but when Ferranti effect occurs then we observe higher voltage on the receiving side.
How does it occurs ?
Ferranti effect basically occurs because of imaginary capacitor and inductor.
This capacitor gets created on its own, its not made intentionally.
We already know that a device that stores electric charge is known as capacitor. It consists of one or more pair of conductors separated by an insulator ( Dielectric medium ).
Here transmission wires act as conductor and air act as dielectric medium.
So the charging current in imaginary capacitor makes an overall current drop in transmission lines that results in voltage gain.
How to reduce Ferranti effect ?
High voltages can create a lot of damage as every electrical circuit / device is designed to work on a specific voltage.
To overcome this effect we use a device called shunt reactor.
It is an inductive element connected in parallel between line and neutral ( on the receiving side ) to reduce the increase in current due to imaginary capacitor.
- Ferranti effect is higher in case of no load or small load.
- It usually occurs in long transmission lines. ( Approximately more than 50 km )
- In short transmission line charging effect is small enough to get neglected.
- It increases with the increase in voltage in transmission lines. It means this effect is observed more in high voltage transmission lines when compared to lower voltage transmission line.
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