| 摘要 |
A protection device for use in conjunction with an electrical appliance having an electrically conductive outer casing and which protects against the casing becoming "live" regardless of the state of a ground connection (GND) associated with an electrical socket to which the appliance is connected. A virtual ground connection is electrically floating with respect to the ground connection (GND) of the electrical socket, and is electrically coupled to the casing of the electrical appliance instead of the ground connection of the electrical socket. A differential comparator circuit compares a fraction of the voltage between the live and neutral connections with a voltage at the virtual ground connection of the appliance, producing a fault signal if a difference between the two voltages exceeds a predetermined threshold. A main feeder interruption device is operatively coupled to the differential comparator circuit, being responsive to the fault signal for opening a switching device connected in at least one of the live and neutral connections. |
