What happens to reactive losses when line loading is above Surge Impedance Loading (SIL)?

When line loading exceeds the Surge Impedance Loading (SIL), reactive losses indeed increase proportionally to the square of the current (I²). SIL represents the point at which the reactive power demand is balanced with the reactive power supply, and when loading is above this threshold, the system becomes less efficient in terms of reactive power management.

In this scenario, the increase in current due to higher loading results in increased reactive losses, as losses in transmission lines are calculated based on the square of the current flowing through them. Specifically, reactive losses occur in the form of I²R losses, where R is the resistance of the transmission line, demonstrating a direct relationship between the current and the losses incurred. Therefore, as current increases significantly, the reactive losses escalate accordingly, which is why this answer is correct.