What causes high voltage on lightly loaded transmission lines?

The phenomenon that causes high voltage on lightly loaded transmission lines is primarily due to the natural capacitance of the line. This capacitance allows the transmission line to store and release energy, which can lead to an increase in voltage under certain conditions, especially when the line is not heavily loaded.

In lightly loaded conditions, the reactive power (often through capacitive charging) can dominate, and because there is not enough load to absorb the reactive power, it can result in voltage rise along the line. This is particularly pronounced in long transmission lines, where the effects of capacitance become more significant. As the line's capacitance interacts with the inductance, it leads to an increase in voltage levels beyond what would be expected from the load alone.

In contrast, other options revolve around different concepts. For instance, while the Ferranti Effect is related to the phenomenon of voltage rise in long lines, it specifically refers to the situation where the receiving end voltage is greater than the sending end voltage due to line capacitance, making it a more specific case rather than a general cause for high voltage in lightly loaded conditions. Surge Impedance Loading deals with the ideal loading condition for a transmission line, and impedance of the system refers to the total resistance and reactance affecting power