Patent ID: 7193827

Claim:
A microcontroller-based system for detecting ground-fault and grounded-neutral conditions in an electrical power distribution system having line and neutral conductors comprising: a sensor circuit containing a single current transformer producing an output signal responsive to current flow in both the line and neutral conductors of the electrical power distribution system, a microcontroller receiving said sensor output signal and initiating the generation of a trip signal upon detection of said ground-fault or said grounded-neutral condition in said power distribution system, said microcontroller being programmed to use said sensor output signal to detect ground-fault conditions during spaced time intervals, and use said sensor output signal to detect grounded-neutral condition during intervening time intervals between said spaced time intervals, a circuit interrupter for interrupting current flow in said power distribution system in response to said trip signal, and a single analog memory circuit operable with both full-wave and half-wave power supplies to provide a timing function to control said spaced time intervals and said intervening time intervals, and a memory function set in response to detection of a ground-fault or grounded-neutral condition to resume a circuit trip if power is temporarily lost before said circuit interrupter activates.