Ferranti Effect in Power Systems

The Ferranti Effect is a phenomenon in electrical power systems where the voltage at the receiving end of a long transmission line

Why It Happens:

• Long transmission lines have capacitance distributed along their length.
• When lightly loaded or open-circuited, the line capacitance charges, causing a leading current.
• This current flows through the line's inductive reactance, resulting in a voltage rise at the receiving end due to the voltage drop being in the direction opposite to the sending end.

Conditions Favoring Ferranti Effect:

• Long transmission lines (typically >200 km).
• Light or no load at the receiving end.
• High voltage systems.
• Underground cables, due to higher capacitance.