In electric power transmission, the characteristic impedance of a transmission line is expressed in terms of the surge impedance loading (SIL), or natural loading, being the power loading at which reactive power is neither produced nor absorbed:
in which is the line-to-line voltage in volts.
Loaded below its SIL, a line supplies reactive power to the system, tending to raise system voltages. Above it, the line absorbs reactive power, tending to depress the voltage. The Ferranti effect describes the voltage gain towards the remote end of a very lightly loaded (or open ended) transmission line. Underground cables normally have a very low characteristic impedance, resulting in an SIL that is typically in excess of the thermal limit of the cable. Hence a cable is almost always a source of reactive power.
Read more about this topic: Characteristic Impedance
Famous quotes containing the words surge and/or loading:
“Timon hath made his everlasting mansion
Upon the beached verge of the salt flood,
Who once a day with his embossed froth
The turbulent surge shall cover; thither come,
And let my grave-stone be your oracle.”
—William Shakespeare (1564–1616)
“Nitrates and phosphates for ammunition. The seeds of war. They’re loading a full cargo of death. And when that ship takes it home, the world will die a little more.”
—Earl Felton, and Richard Fleischer. Captain Nemo (James Mason)