Transmission line transfer capability is determined by which characteristics?

Transmission line transfer capability refers to the maximum amount of electrical power that can be transmitted across a transmission line without violating operational limits such as thermal limits, voltage drop, and system stability. The characteristics that determine this capability primarily involve the current load on the system, the voltage levels being maintained, and the impedance of the transmission line itself.

System loading is crucial because it reflects the actual demand on the transmission line; higher loading can increase the thermal stress and limit the amount of power that can be safely transmitted. Voltage is important as it can influence the line's performance and stability during power transfer. Impedance, which includes both resistive and reactive components, affects the line's efficiency and the overall power flow; higher impedance can lead to greater power losses and lower transfer capabilities.

By focusing on these three characteristics — system loading, voltage, and impedance — operators can analyze and optimize the transmission line's performance in real-time, leading to more efficient and reliable power delivery. Other options, while they may address other aspects of the system, do not accurately capture the critical factors that directly influence a transmission line’s transfer capability.