Patent ID: 8446699
Filing Date: 2013-05-21
Classification: H02H

Abstract:
1. A residual current device having a trip mechanism for isolating an electric supply to an electrical installation upon detection of a predetermined current imbalance between the line and neutral conductors of said electric supply, comprising: a current transformer having the line and neutral conductors inductively coupled as a primary winding; a secondary winding inductively coupled to said current transformer and connectable to said trip mechanism, said secondary winding being responsive to said current imbalance on said electrical installation; and a circuit protection winding inductively coupled to said current transformer and responsive to said current imbalance on said electrical installation, said circuit protection winding being connectable to a processing means for processing if said current imbalance exceeds said predetermined current imbalance, the impedance of said processing means varies according to the level of said line voltage, wherein the impedance of said processing means is varied using an amplifier means, and wherein if said line voltage is below a predetermined threshold voltage, the impedance of said amplifier means is sufficiently high so that any current imbalance on said electrical installation predominately flows in said secondary winding, or, if said line voltage is above said predetermined threshold voltage, the impedance of said amplifier means is sufficiently low so that any current imbalance on said electrical installation predominately flows in said circuit protection winding.