The characteristics of the amplitude function of real signals are obtained by means of Hilbert transform，and the distinction between the current amplitude function when a fault occurs before and after the series capacitors is analyzed.When the fault occurs in front of the capacitors，the amplitude function cannot characterize the envelope curve of the fault current.On the contrary，the amplitude function can characterize the envelope curve of the fault current when the fault occurs after the capacitors.Accordingly，a new fault point recognition criterion for series compensated lines is derived based on the Hilbert transform.It is integrated with the traditional distance protection to form a new series compensated line protection scheme which can effectively avoid the overreach problem and ensure sufficient sensitivity.The availability of this scheme is verified by PSCAD simulation.