Arc fault circuit interrupter with upstream impedance detector

A system of protective devices, comprising:

• an overcurrent protection device installed at an origin of a branch circuit for interrupting current when an overcurrent condition is present;
• a fault protection device installed at an outlet in said branch circuit;
• wherein said fault protection device includes measuring means for measuring an impedance in at least a portion of said branch circuit and means for producing a signal when said measured impedance exceeds a predetermined value;
• wherein said system of protective devices affords series fault and parallel arc fault protection to at least a portion of said electrical branch circuit.

In an electrical protection device, protective of an electrical power distribution system supplying voltage from a secondary winding of a transformer through an electrically conductive path to said protection device, wherein said device includes a plurality of line terminals which receive voltage from said electrically conductive path, a plurality of load terminals for delivering voltage from said secondary winding of said transformer to a load, and a plurality of interrupting contacts between said load terminals and said line terminals;

• a method for protecting said electrical power distribution system, comprising the steps of:
• measuring an impedance of said path;
• and
• producing a signal when said measured impedance exceeds a pre-determined threshold;
• wherein said signal causes said interrupting contacts to disconnect said load terminals from said line terminals.

In an electrical protection device, protective of an electrical power distribution system supplying voltage from a secondary winding of a transformer through an electrically conductive path to said protection device, wherein said device includes a plurality of line terminals which receive voltage from said electrically conductive path, and a plurality of load terminals for delivering voltage from said secondary winding of said transformer to a load;

• a method for protecting said electrical power distribution system, comprising the steps of:
• generating a voltage signal to produce a test current in at least a portion of said electrical power distribution system;
• measuring a signal responsive to said voltage signal;
• and
• comparing said measured signal against a pre-determined reference signal to determine a fault condition within said portion of said electrical power distribution system.