In transmission lines, variation in voltage at the receiving end, expressed as a percentage of full load voltage at the receiving end, when full load at a given power factor is removed with voltage at the sending end being kept constant is called:

The correct answer is option 1.

Voltage regulation

“Voltage regulation is defined as the ratio of the difference between sending and receiving end voltage to receiving end voltage of a transmission line between the conditions of no load and full load”.

\(VR={V_{R(no \space load)}-V_{R(full\space load)}\over V_R}\)

The receiving end voltage at no-load condition is given by:

\(V_S=AV_R+BI_R\)

At no-load, I_R = 0

\(V_S=AV_R+BI(0)\)

\(V_{R(no\space load)}={V_S\over A}\)

and \(V_{R(full\space load)}=V_R\)

The expression for the voltage regulation in the transmission line is:

\(VR={{V_{S}\over A}-V_{R}\over V_R}\)