GATE Electrical Engineering (EE) Test: Performance of Transmission Lines,

Power system network :

Hence, option (A) will not be correct.

The fictitious conductor is one whose radius is r' and whose diameter is therefore,

Inductance,

Here, GMR radius of conductor.
Hence, if radius increases, GMR also increases. As a result of which inductance will decrease.

For underground cable, Z_s = 40 Ω
For overhead line, Z_s = 400 Ω

Dielectric loss occurs in underground cables not in a transmission line.

Surge impedance of the line is given by

or, 

Zero regulation of a transmission line occurs at a leading power factor when φ = θ.
Since R = X

Shunt reactors are used to bring down receiving end voltage during light load or no-load condition to overcome Ferranti effect.

Option A is correct.

The maximum active power transferable over a lossless line is given by P = (V_s V_r / X) sin δ, where δ is the power-angle difference between sending and receiving ends.

Maximum power occurs at δ = 90°, giving P_max = V_s V_r / X. Operating near this limit means the system has very little stability margin; a small disturbance can push the rotor angle beyond the stable region and cause loss of synchronism.

Increased loading does raise currents and therefore I²R losses, which reduces transmission efficiency, and reactive limits can degrade the voltage profile. These are important secondary effects but the primary constraint when loading approaches the maximum transfer capability is the power-angle (stability) limit.

Hence, stability is the main quantity impaired when operating close to maximum power transfer capability.