What happens to the voltage phase angle difference when the receiving end load of a transmission line is suddenly increased?

When the receiving end load of a transmission line is suddenly increased, the voltage phase angle difference tends to increase. This phenomenon occurs due to the need for more active power to meet the higher load demand. As the load increases, the current flowing through the transmission line also increases, leading to a higher voltage drop across the line's impedance. This voltage drop causes the phase angle at the receiving end to shift further away from that at the sending end, resulting in an increased phase angle difference.

In a balanced power system, the relationship between current and voltage is expressed in terms of their angles. When load demand increases suddenly, the supply must respond to the change in load, which can alter the current flow and subsequently the angles. Therefore, a greater phase angle difference is needed to account for the increased power demand, leading to an increase in the phase angle. The increased phase angle indicates that more reactive power is also potentially required to maintain voltage stability under the new load conditions.

Understanding how phase angles relate to load can help in managing transmission systems and ensuring reliability in electricity delivery.