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Voltage regulation can be negative when power factor will be
Lagging
Leading
Unity
Zero
Leading
Voltage regulation is defined as the change in voltage at the receiving end of a transmission line between no-load and full-load conditions, expressed as a percentage of the full-load voltage. It becomes negative when the receiving-end voltage at full-load is greater than the receiving-end voltage at no-load, which occurs due to the Ferranti effect or capacitive compensation.
Voltage regulation is defined as the change in voltage at the receiving end of a transmission line between no-load and full-load conditions, expressed as a percentage of the full-load voltage. It becomes negative when the receiving-end voltage at full-load is greater than the receiving-end voltage at no-load, which occurs due to the Ferranti effect or capacitive compensation.
%Regulation=VfullтИТloadтАЛVnoтИТloadтАЛтИТVfullтИТloadтАЛтАЛ├Ч100
VrтАЛ=VsтАЛтИТI(Rcos╧Х┬▒Xsin╧Х)
In a transmission line with significant shunt capacitance, leading power factor loads provide reactive power that partially cancels the inductive voltage drop of the series impedance. When the current is leading, the voltage drop vector across the line impedance (I(R+jX)) can result in a receiving end voltage VrтАЛ higher than the sending end voltage VsтАЛ (or equivalent open-circuit voltage), making the regulation VregтАЛ=VflтАЛVnlтАЛтИТVflтАЛтАЛ├Ч100 negative.
Leading power factor loads act as a source of reactive power, compensating for line inductance.
Negative regulation is typically observed in long transmission lines at light loads or leading power factors.
Unity power factor regulation is always positive for inductive transmission lines.
The Ferranti effect is a specific case of negative regulation occurring on long lines at no-load.
Improves voltage profile along the transmission line.
Reduces the requirement for external reactive power compensation equipment.
Risk of overvoltage at the receiving end during light load conditions.
Potential for insulation stress due to high voltage at the load end.
Long distance power transmission lines.
Systems with high shunt capacitive effect.
For lagging power factor, the voltage drop across the series impedance adds to the sending end voltage, leading to positive regulation.
At leading power factor, the reactive voltage drop component is subtracted from the reference voltage, causing VrтАЛ>VsтАЛ.
B is correct тАФ Voltage regulation becomes negative at a leading power factor because the reactive power generated by the line's shunt capacitance (or the load's capacitance) results in a receiving-end voltage that is higher than the no-load voltage.
Always remember that for a standard inductive transmission line, lagging power factor always leads to positive regulation, while leading power factor can result in negative regulation.