The expression for voltage regulation of a short transmission line for leading power factor is given by: ____, where, 'I' is the line current, 'V_r' is the receiving end voltage, 'R' is the line resitance and 'X' is the line reactance.

• A. (IRcosφ_r - IXsinφ_r)/V_r
• B. (IXcosφ_r - IRsinφ_r)/V_r
• C. (IRcosφ_r + IXsinφ_r)/V_r
• D. (IXcosφ_r + IRsinφ_r)/V_r

Answer: (A)

For lagging power factor = (IR*cosφ + IXsinφ)/V_r
For leading power factor = (IR*cosφ - IXsinφ)/V_r
Zero voltage regulation occurs on leading power factor only.