Detection method for local discharge

The present invention provides a detection method for a local discharge, having a well detection sensitivity to a local discharge signal. A low impedance by-path conductor (21) having a capacitor and arranged between a metal armourings (13A, 13B) connected through an insulating barrel (14) is used as a sensing loop, a local discharge current flowing into the by-path conductor (21) is detected by a high-frequency converter (30), thus it is easy to separate the local discharge signals from a commercial frequency current, moreover, a foreign noise radiated or transmitted by a space is not easy to overlap with the local discharge signals, thus the detection sensitivity may be improved.