What does a net VAR flow out of a high voltage transmission line indicate?

A net VAR flow out of a high voltage transmission line indicates that the line is lightly loaded. When a transmission line is lightly loaded, it is capable of supplying reactive power (measured in VARs). Reactive power is necessary for maintaining voltage levels across the system and is often needed for the operation of inductive loads like motors.

In a lightly loaded condition, the reactive power produced by the line is greater than the reactive power consumed, resulting in a net flow of VARs out of the line. This condition can lead to voltage rise issues if not managed properly.

In contrast, a heavily loaded line would typically consume more reactive power, resulting in a net VAR flow into the transmission line. Being at Surge Impedance Loading refers to a condition where the line is matched to its optimal loading, and efficiency is more related to how well power is being transmitted without losses rather than the reactive power flow itself.