Proposal of Detection Method of Leakage Current between Electrodes of a Contaminated and Wetted Cord Plug by Superimposed High Frequency Signal

Abstract

Tracking of a cord plug caused by leakage current flowing between its electrodes, which is observed under contaminated and wetted conditions, is attributed to one of the causes of fire accidents. Demands of society for establishment of countermeasures against this type of tracking have become stronger since the number of fire accidents by the tracking has been increased in the recent ten years. However, it seems rather difficult to detect the leakage current because its magnitude is much smaller than that of a typical load current of a household appliance.In this paper, a novel method to detect the existence of the leakage current is proposed, where a high frequency signal superimposed on a load current is detected instead of detecting the leakage current itself. It was confirmed by laboratory experiments that the signal could be detected only when wetted dust was in the space between a cord plug and an outlet. The proposed method seems promising to detect of tracking of a cord plug with high frequency signal.