Is it possible to have current in a transmission line, under no-load conditions?

• A. Yes, because of the corona effect
• B. No, because of the proximity effect
• C. Yes, because of the capacitance effect
• D. Yes, because of skin effect

Answer: (C)

During the no-load condition, the current flowing is only charging current due to line capacitance. It increases the capacitive var in the system. Since the line is under no load the line inductance will be less. Therefore, the capacitive var becomes greater than inductive var during no load or light load condition. Due to this phenomenon, the receiving end voltage becomes greater than the sending end voltage. This effect is also called the Ferranti effect.
In the case of short lines, the effect is negligible, but it increases rapidly with the increase in the length of the line. Therefore, this phenomenon is observable only in medium and long lines. For long high voltage and EHV transmission lines, shunt reactors are provided to absorb a part of the charging current or shunt capacitive VAr of the transmission line under no load or light load conditions, in order to prevent the overvoltage on the line.