Leakage current detection and interruption circuit

• US 7,751,161 B2
• Filed: 12/30/2005
• Issued: 07/06/2010
• Est. Priority Date: 01/04/2005
• Status: Expired due to Fees

• Current Assignee: Technology Research Group LLC (Southwire Company)
• Original Assignee: Technology Research Corporation (Southwire Company)
• Inventors: Williams, Thomas S.
• Primary Examiner(s): Paladini; Albert W
• Assistant Examiner(s): Patel; Dharti H
• Application Number:
  US11/324,087
• Publication Number:
  US 20060146456A1
• Time in Patent Office: 1,649 Days
• Field of Search: 361/42, 361 44- 45, 361/47, 361 49- 50, 361/93.1
• US Class Current: 361/42
• CPC Class Codes: H01H 73/44 reset by push-button, pull-knob or slide
• CPC Class Codes: H01H 83/02 operated by earth fault currents H01H83/14 takes precedence
• CPC Class Codes: H02H 1/0038 concerning the connection of the detecting means, e.g. for reducing their number
• CPC Class Codes: H02H 1/0069 by means of light or heat rays
• CPC Class Codes: H02H 3/044 Checking correct functioning of protective arrangements, e.g. by simulating a fault for differential current circuit breakers H02H3/335
• CPC Class Codes: H02H 3/16 responsive to fault current to earth, frame or mass with balanced or differential arrangement H02H3/26 ; monitoring earth connection H02H5/105
• CPC Class Codes: H02H 3/32 involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors
• CPC Class Codes: H02H 3/33 using summation current transformers H02H3/347 takes precedence
• CPC Class Codes: H02H 5/10 responsive to mechanical injury, e.g. rupture of line, breakage of earth connection

Abstract

A circuit is disclosed for disconnecting a power source upon the detection of a leakage. The circuit comprises a disconnect switch for disconnecting the power source. A primary circuit controls the disconnect switch. A secondary circuit senses a leakage current. An optical switch interconnects the primary circuit and the secondary circuit for opening the disconnect switch upon the secondary circuit sensing a leakage current. The circuit is suitable for use as a leakage current detection and interruption circuit for completely electrically disconnecting and isolating the power source and the primary circuit from the secondary circuit.

Claims

1. A circuit for disconnecting a power source upon the detection of a leakage current from one of a first and a second wire connected to the power source, comprising:

a disconnect switch interposed within the first and second wires connected to the power source;

said disconnect switch defining a primary side and a secondary side of said disconnect switch with said primary side located adjacent to said power source;

a primary circuit including a photoconductive switch located on said primary side of said disconnect switch for controlling said disconnect switch;

a secondary circuit located on said secondary side of said disconnect switch;

said secondary circuit including a sensing conductor located adjacent to the first and second wires for sensing a leakage current from the first and second wires;

said secondary circuit comprising a light emitting device connected in series with a resistor between said sensing conductor and both of the first and second wires for actuating said light emitting device upon a leakage current flow between said sensing conductor and one of the first and second wires; and

said photoconductive switch being optically coupled to said light emitting device for opening said disconnect switch upon said secondary circuit sensing a leakage current between said sensing conductor and one of the first and second wires.

2. A circuit as set forth in claim 1, wherein said sensing conductor includes a shield sensing conductor located about at least one of the first and second wires connected to the power source.

3. A circuit as set forth in claim 1, wherein said sensing conductor includes a shield sensing conductor located about both of the first and second wires connected to the power source.

4. A circuit as set forth in claim 1, wherein said photoconductive switch and said light emitting device completely electrically isolates the power source and completely electrically isolates said primary circuit from secondary circuit upon the opening of said disconnect switch.

5. A circuit as set forth in claim 1, wherein said light emitting device comprises a light emitting diode.

6. A circuit as set forth in claim 1, wherein said disconnect switch includes a normally open solenoid operated switch;

a mechanical latch mechanism for maintaining said disconnect switch in a closed condition; and

said primary circuit operating said mechanical latch mechanism for opening said solenoid operated switch upon said secondary circuit sensing a leakage current from one of the first and second wires.

7. A circuit for disconnecting a power source upon the detection of a leakage current from one of a first and second wire connected to the power source, comprising:

a disconnect switch interposed within the first and second wires connected to the power source;

said disconnect switch defining a primary side and a secondary side of said disconnect switch with said primary side located adjacent to said power source;

a primary circuit including a photoconductive switch located on said primary side of said disconnect switch for controlling said disconnect switch;

a secondary circuit located on said secondary side of said disconnect switch;

said secondary circuit including a sensing conductor located adjacent to the first and second wires for sensing a leakage current from the first and second wires;

a secondary circuit comprising a non-reactive divider circuit connected between the first and second wires for providing a divider node between the first and second wires;

a light emitting device located in said secondary circuit and connected between said divider node and said sensing conductor for illuminating said light emitting device upon a leakage current flowing between said sensing conductor and one of the first and second wires; and

said photoconductive switch being optically coupled to said light emitting device for opening said disconnect switch upon said secondary circuit sensing a leakage current between said sensing conductor and one of the first and second wires.

8. A circuit for disconnecting a power source upon the detection of a leakage current from one of a first and second wire connected to the power source, comprising:

a disconnect switch interposed within the first and second wires connected to the power source;

said disconnect switch defining a primary side and a secondary side of said disconnect switch with said primary side located adjacent to said power source;

a primary circuit including a photoconductive switch located on said primary side of said disconnect switch for controlling said disconnect switch;

a secondary circuit located on said secondary side of said disconnect switch;

said secondary circuit including a sensing conductor located adjacent to the first and second wires for sensing a leakage current from the first and second wires;

a secondary circuit comprising a resistive voltage divider circuit connected between the first and second wires for providing a voltage divider node between the first and second wires;

a light emitting device located in said secondary circuit and connected between said voltage divider node and said sensing conductor for illuminating said light emitting device upon a leakage current flowing between said sensing conductor and one of the first and second wires; and

said photoconductive switch being optically coupled to said light emitting device for opening said disconnect switch upon said secondary circuit sensing a leakage current between said sensing conductor and one of the first and second wires.

10. A circuit as set forth in claim 8, wherein said driver switch of said primary circuit includes a silicon controlled rectifier for opening said disconnect switch upon said secondary circuit sensing a leakage current from the wire.

9. A circuit for disconnecting a power source upon the detection of a leakage current from one of a first and second wire connected to the power source, comprising:

a disconnect switch interposed within the first and second wires connected to the power source;

said disconnect switch defining a primary side and a secondary side of said disconnect switch with said primary side located adjacent to said power source;

said disconnect switch comprising a disconnect switch coil for changing said disconnect switch from a closed position connecting said power source to the first and second wires to an open position for disconnecting power source from the first and second wires upon a threshold current flow through said disconnect switch coil;

a primary circuit located on said primary side of said disconnect switch for controlling said disconnect switch;

said primary circuit comprising a driver switch connected in series with said disconnect switch coil across the power source for providing said threshold current flow through said disconnect switch coil upon actuation of said driver switch;

a secondary circuit located on said secondary side of said disconnect switch including a sensing conductor located adjacent to the first and second wires;

said secondary circuit having a light emitting device connected for illuminating said light emitting device upon a leakage current flowing between said sensing conductor and one of the first and second wires;

a photoconductive switch located in said primary circuit and optically coupled to said light emitting device located in said secondary circuit;

a resistor connected in series with said coil across the power source for providing a reduced current flow through said coil below said threshold current required to open said disconnect switch to supply an operating voltage to said photoconductive switch; and

said photoconductive switch connected to said driver switch for actuating said driver switch upon said secondary circuit sensing a leakage current in said sensing conductor to open said disconnect switch for electrically disconnecting the power source from the first and second wires.

11. A circuit for disconnecting a power source upon the detection of a leakage current from one of a first and second wire connected to the power source, comprising:

a disconnect switch interposed within the first and second wires connected to the power source;

said disconnect switch defining a primary side and a secondary side of said disconnect switch with said primary side located adjacent to said power source;

said disconnect switch comprising a disconnect switch coil for changing said disconnect switch from a closed position connecting said power source to the first and second wires to an open position for disconnecting power source from the first and second wires upon a threshold current flow through said disconnect switch coil;

a primary circuit located on said primary side of said disconnect switch for controlling said disconnect switch;

said primary circuit comprising a driver switch connected in series with said disconnect switch coil across the power source for providing said threshold current flow through said disconnect switch coil upon actuation of said driver switch;

a secondary circuit located on said secondary side of said disconnect switch including a sensing conductor located adjacent to the first and second wires;

said secondary circuit having a light emitting device connected for illuminating said light emitting device upon a leakage current flowing between said sensing conductor and one of the first and second wires;

a photoconductive switch located in said primary circuit and optically coupled to said light emitting device located in said secondary circuit;

a resistor connected in series with said coil across the power source and in parallel with said driver switch for providing a reduced current flow through said coil below said threshold current required to open said disconnect switch to supply an operating voltage to said photoconductive switch; and

said photoconductive switch connected to said driver switch for actuating said driver switch upon said secondary circuit sensing a leakage current in said sensing conductor to open said disconnect switch for electrically disconnecting the power source from the wire.

12. A circuit for disconnecting a power source upon the detection of a leakage current from one of a first and second wire connected to the power source, comprising:

a disconnect switch interposed within the first and second wires connected to the power source;

said disconnect switch defining a primary side and a secondary side of said disconnect switch with said primary side located adjacent to said power source;

said disconnect switch comprising a disconnect switch coil for changing said disconnect switch from a closed position connecting said power source to the first and second wires to an open position for disconnecting power source from the first and second wires upon a threshold current flow through said disconnect switch coil;

a primary circuit located on said primary side of said disconnect switch for controlling said disconnect switch;

said primary circuit comprising a driver switch connected in series with said disconnect switch coil across the power source for providing said threshold current flow through said disconnect switch coil upon actuation of said driver switch;

a diode connected in series with said disconnect switch coil across the power source;

a secondary circuit located on said secondary side of said disconnect switch including a sensing conductor located adjacent to the first and second wires;

said secondary circuit having a light emitting device connected for illuminating said light emitting device upon a leakage current flowing between said sensing conductor and one of the first and second wires;

a photoconductive switch located in said primary circuit and optically coupled to said light emitting device located in said secondary circuit;

a resistor connected in series with said coil across the power source and in parallel with said driver switch for providing a reduced current flow through said coil below said threshold current required to open said disconnect switch to supply an operating voltage to said photoconductive switch; and

said photoconductive switch connected to said driver switch for actuating said driver switch upon said secondary circuit sensing a leakage current in said sensing conductor to open said disconnect switch for electrically disconnecting the power source from the wire.

13. A circuit for disconnecting a power source upon the detection of a leakage current from one of a first and a second wire connected to the power source, comprising:

a disconnect switch interposed within the first and second wires connected to the power source;

said disconnect switch defining a primary side and a secondary side of said disconnect switch with said primary side located adjacent to said power source;

a primary circuit including a photoconductive switch located on said primary side of said disconnect switch for controlling said disconnect switch;

said primary circuit comprising a driver switch connected in series with said disconnect switch coil across the power source for providing said threshold current flow through said disconnect switch coil upon actuation of said driver switch;

a diode connected in series with said disconnect switch coil across the power source;

a resistor connected in series with said disconnect switch coil across the power source and in parallel with said driver switch for providing reduced current flow through said coil below said threshold current required to open said disconnect switch to supply an operating voltage to said photoconductive switch;

a secondary circuit located on said secondary side of said disconnect switch;

said secondary circuit including a sensing conductor located adjacent to the first and second wires for sensing a leakage current from the first and second wires

said secondary circuit comprising a non-reactive divider circuit connected between the first and second wires for providing a divider node between the first and second wires;

a light emitting device located in said secondary circuit and connected between said divider node and said sensing conductor for illuminating said light emitting device upon a leakage current flowing between said sensing conductor and one of the first and second wires; and

said photoconductive switch being optically coupled to said light emitting device for opening said disconnect switch upon said secondary circuit sensing a leakage current in said sensing conductor for completely electrically isolating said primary circuit from secondary circuit upon the opening of said disconnect switch.