Ferranti effect...

A long transmission line receiving end voltage is higher than the sending end voltage. If such a line is open circuited or very lightly loaded at the receiving end.

 This is known as ferranti effect. This is due to the voltage drop across the line inductance  (due to the charging current) being in phase with the sending end voltage. Thus both capacitance and inductance are necessary to produce this effect. This phenomenon occurs only in medium and long transmission lines.

Topics List - Electrical