📘 Ferranti Effect – Long Transmission Line
Ferranti Effect occurs in long transmission lines under light load condition. Receiving end voltage becomes greater than sending end voltage.
🔹 1️⃣ What is Ferranti Effect?
Under light or no load condition: Vr > Vs
Receiving end voltage rises above sending end voltage.🔹 2️⃣ Why Does It Occur?
In long lines:- Line capacitance is significant
- Charging current flows
- Voltage drop across inductance due to charging current adds to Vr
🔹 3️⃣ Mathematical Explanation
For long line: Vs = A Vr + B Ir At no load: Ir = 0 Therefore:Vs = A Vr
For long line: A = cosh(γl) Since cosh(γl) > 1 Vr = Vs / A But due to distributed capacitance, effective voltage rises. Conceptual explanation frequently asked.🔹 4️⃣ Conditions for Ferranti Effect
- Long transmission line (>250 km)
- Light load or no load
- High operating voltage
🔹 5️⃣ Example Concept Question
A 300 km line operating at no load. What happens to receiving end voltage?Answer: It increases due to Ferranti effect.
🔹 6️⃣ How to Reduce Ferranti Effect?
- Shunt reactors at receiving end
- Reduce line length
- Load the line properly
🎯 GATE Important Points
- Occurs in long lines
- Due to line capacitance
- More at light load
- Receiving end voltage rises
Ferranti Effect = Voltage Rise Due to Line Capacitance
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