GFCI ground fault current filtering

摘要

A system for controlling the response of a ground fault circuit interrupter in the presence of random leakage currents due to the presence of a conductive media such as water or ice. The signal from a magnetic core differential transformer is applied to two filters in parallel. The first filter passes the fundamental frequency of the source and the second filter passes a broad band of frequencies starting at twice the fundamental frequency. The output of the filters are applied to a microprocessor which manipulates the filter outputs and compares certain of the filter outputs to a stored pattern of expected current leakage. The microprocessor operates a relay to disconnect the load from the source when a fault condition exists.