The capacitance of an overhead line is the ability of the conductors to store electrical energy due to the electric field that exists between the conductors and the ground. It acts like a capacitor, with the conductors serving as the plates and the air as the dielectric medium. For a single-phase line with two conductors, this capacitance is determined by the radius of the conductors and the distance between them.

Capacitance is a crucial parameter in power system analysis, especially for medium and long-distance lines. It directly affects the line's performance and can lead to issues like the Ferranti effect (where the receiving-end voltage is higher than the sending-end voltage under light or no-load conditions) and the flow of charging current. Proper consideration of line capacitance is essential for maintaining voltage stability and preventing equipment damage.