What happens when a transmission line is above SIL?

When a transmission line operates above its Surge Impedance Loading (SIL), it indicates that the line is carrying more load than it is optimally designed to handle. At this point, the line is no longer functioning in its ideal state and begins to absorb reactive power (VAR) from the system rather than supplying it.

This phenomenon occurs due to the capacitive nature of transmission lines, where the line becomes less effective at transmitting power efficiently as the load increases beyond SIL. Instead of providing reactive support to adjacent loads or systems, the line starts to absorb VARs, which can contribute to voltage stability issues in the system. This absorption affects the overall power system dynamics and can lead to a scenario where other generating units or reactive power sources need to compensate for this absorbed VAR.

In contrast, the other options do not accurately reflect the behavior of transmission lines beyond their SIL. Therefore, option B is the most accurate description of what happens when a transmission line operates above its SIL.