What are the effects of transmission line loading above its surge impedance loading?

When transmission lines are loaded above their surge impedance loading, they primarily behave like a reactor. This phenomenon occurs because when the loading exceeds the surge impedance level, the line’s characteristics shift into the reactive region, leading to an increase in reactive power.

In this scenario, the excess load causes the line to produce reactive power rather than merely transferring active power. Essentially, this means that the line’s impedance influences how it interacts with the electrical current flowing through it.

As a result, the line will exhibit behavior similar to that of an inductor, absorbing reactive power and causing a lagging power factor. This is an important consideration for system operators, as it can lead to voltage stability issues and requires careful monitoring and management of reactive power levels on the network. The other options do not accurately reflect the behavior of transmission lines under these conditions, making the understanding of the line acting as a reactor crucial for effective power system management.