Patent ID: 6023400
Filing Date: 2000-02-08
Classification: H02H

Abstract:
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 supply to which the appliance is connected, the electrical appliance having live and neutral terminals for feeding current to the appliance from respective live and neutral feeders of the electrical supply, said device being comprising:a virtual ground connection which is electrically floating with respect to the ground connection (GND) of the electrical supply, said virtual ground connection for electrically coupling to the casing of the electrical appliance instead of the ground connection of the electrical supply, anda differential comparator circuit for comparing a fraction of the voltage between the live and neutral connections with a voltage at the virtual ground connection of the appliance and producing a fault signal if a difference between said voltages exceeds a predetermined threshold.