Leakage current detection and interruption circuit with improved shield

• US 7,623,329 B2
• Filed: 07/07/2006
• Issued: 11/24/2009
• 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: Gandolfi, Paul R., Brugner, Frank S. Jr., Williams, Thomas S.
• Primary Examiner(s): Paladini; Albert W
• Assistant Examiner(s): Patel; Dharti H
• Application Number:
  US11/482,251
• Publication Number:
  US 20070159740A1
• Time in Patent Office: 1,236 Days
• Field of Search: 361 44- 45, 361/47, 361 49- 50, 361/93.1, 361/42
• 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 3/33 using summation current transformers H02H3/347 takes precedence

Abstract

A circuit is disclosed for disconnecting a power source upon the detection of a leakage current comprising a power cable having an insulated first and a second wire. The power cable has a conductive shield surrounding the first and second wires with a drain wire electrically contacting the conductive shield. A disconnect switch is interposed between the power source and the power cable. A primary circuit controls the disconnect switch. A secondary circuit is connected to the drain wire for sensing a leakage current between the conductive shield and one of the first and second wires. An optical switch interconnects the primary circuit and the secondary circuit for opening the disconnect switch upon the secondary circuit sensing a leakage current.

Claims

1. A circuit for disconnecting a power source upon the detection of a leakage current, comprising:

a power cable comprising an insulated first wire and an insulated second wire;

said power cable having a conductive shield surrounding said insulated first wire and said insulated second wire;

a drain wire having a first and a second portion;

said first portion of said drain wire being non-insulated and in electrical contact with said conductive shield;

an outer insulating layer molded about said conductive shield;

a disconnect switch interposed between the power source and said power cable;

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

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 second side of said disconnect switch comprising a light emitting device being connected in series with a resistor between said drain wire and both of said insulated first wire and said insulated second wire for actuating said light emitting device upon a leakage current flow between said conductive shield and one of said insulated first wire and said insulated second wire; and

said photoconductive switch optically coupled to said light emitting device for interconnecting said primary circuit and said secondary circuit for opening said disconnect switch upon said secondary circuit sensing a leakage current between said conductive shield and one of said insulated first wire and said insulated second wires.

2. A circuit for disconnecting a power source as set forth in claim 1, wherein said conductive shield is a metallic foil.

3. A circuit for disconnecting a power source as set forth in claim 1, wherein said conductive shield comprises a metallic mesh.

4. A circuit for disconnecting a power source as set forth in claim 1, wherein said conductive shield comprises a polymeric material with a metallic conductive coating.

5. A circuit for disconnecting a power source as set forth in claim 1, wherein said conductive shield comprises an organic conductive polymeric material.

6. A circuit for disconnecting a power source as set forth in claim 1, wherein said first portion of said drain wire extends along substantially the total length of said conductive shield.

7. A circuit for disconnecting a power source as set forth in claim 1, wherein said drain wire is located internal to said conductive shield.

8. A circuit for disconnecting a power source as set forth in claim 1, wherein said drain wire is located external to said conductive shield.

9. A circuit for disconnecting a power source as set forth in claim 1, wherein said outer insulating layer establishes a mechanical engagement between said first portion of said drain wire and said conductive shield to provide an electrical connection between said drain wire and said conductive shield.

10. A circuit for disconnecting a power source as set forth in claim 1, wherein said outer insulating layer establishes a resilient mechanical engagement between said first portion of said drain wire and said conductive shield to provide an electrical connection between said drain wire and said conductive shield.

11. A circuit for disconnecting a power source as set forth in claim 1, wherein said primary circuit includes a silicon controlled rectifier for opening said disconnect switch upon said secondary circuit sensing a leakage current from said drain wire.

12. A circuit for disconnecting a power source as set forth in claim 1, wherein said disconnect switch comprises a disconnect switch coil for changing said disconnect switch from a closed position connecting said power cable to the power source to an open position for disconnecting said power cable from the power source;

and

said primary circuit including a thyristor connected in series with said disconnect switch coil for changing said disconnect switch into said open position upon said secondary circuit sensing said leakage current to disconnect said power cable from the power source.

13. A circuit for disconnecting a power source from a load, the power source having a line socket and a neutral socket, comprising:

a housing having a line lug and a neutral lug for insertion within said line socket and said neutral socket of the power source;

a power cable comprising an insulated first wire and an insulated second wire;

said power cable having a conductive shield surrounding said insulated first wire and said insulated second wire;

a drain wire having a non-insulated portion in contact with said conductive shield;

an outer insulating layer molded about said conductive shield;

disconnect switch located in said housing interconnecting said line lug and said neutral lug of said housing to said insulated first wire and said insulated second wire of said power cord;

a primary circuit located between said disconnect switch and the power source for controlling said disconnect switch;

a secondary circuit located on said secondary of said disconnect switch comprising a non- capacitive divider circuit connected between said insulated first wire and said insulated second wire for providing a divider node between said insulated first wire and said insulated second wire;

said primary circuit and said secondary circuit being located in said housing;

a light emitting device located in said secondary circuit and connected between said divider node and said drain wire for illuminating said light emitting device upon a leakage current flowing between one of said insulated first and second wires and said conductive shield; and

an optical switch located in said primary circuit and optically coupled to said light emitting device located in said secondary circuit for opening said disconnect switch upon said secondary circuit sensing a leakage current from said drain wire for completely electrically disconnecting the power source from the load and completely electrically disconnecting said primary circuit and said secondary circuit.

14. A circuit for disconnecting a power source upon the detection of a leakage current, comprising:

a power cable comprising an insulated first wire and an insulated second wire;

said power cable having a conductive shield surrounding said insulated first wire and said insulated second wire;

a drain wire having a first and a second portion;

said first portion of said drain wire being non-insulated and in electrical contact with said conductive shield;

an outer insulating layer molded about said conductive shield;

a disconnect switch interposed between the power source and said power cable;

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

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 of said disconnect switch comprising a resistive voltage divider circuit connected between said insulated first wire and said insulated second wire for providing a voltage divider node between said insulated first wire and said insulated second wire;

a light emitting device located in said secondary circuit and connected between said voltage divider node and said drain wire for illuminating said light emitting device upon a leakage current flowing between one of said insulated first and second wires and said conductive shield;

a secondary circuit located on said secondary of said disconnect switch comprising a light emitting device being connected in series with a resistor between said drain wire and both of said insulated first wire and said insulated second wire for actuating said light emitting device upon a leakage current flow between said conductive shield and one of said insulated first wire and said insulated second wire; and

said photoconductive switch optically coupled to said light emitting device for interconnecting said primary circuit and said secondary circuit for opening said disconnect switch upon said secondary circuit sensing a leakage current between said conductive shield and one of said insulated first wire and said insulated second wires.

15. A circuit for disconnecting a power source upon the detection of a leakage current, comprising:

a power cable comprising an insulated first wire and an insulated second wire;

said power cable having a conductive shield surrounding said insulated first wire and said insulated second wire;

a drain wire having a first and a second portion;

said first portion of said drain wire being non-insulated and in contact with said conductive shield;

an outer insulating layer molded about said conductive shield;

a disconnect switch interposed between the power source and said power cable;

a primary circuit for controlling said disconnect switch;

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

a driver switch located in said primary circuit 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 of said disconnect switch having a light emitting device connected to said drain wire for illuminating said light emitting device upon a leakage current flowing between one of said insulated first and second wires and said conductive shield;

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 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 being connected to said driver switch for opening said disconnect switch upon said secondary circuit sensing a leakage current from said drain wire for completely electrically disconnecting the power source from the load and completely electrically disconnecting said primary circuit and said secondary circuit.

16. A circuit for disconnecting a power source upon the detection of a leakage current, comprising:

a power cable comprising an insulated first wire and an insulated second wire;

said power cable having a conductive shield surrounding at least one of said insulated

first wire and said insulated second wire;

a drain wire having a first and a second portion;

said first portion of said drain wire being non-insulated and in contact with said conductive shield;

an outer insulating layer molded about said conductive shield;

a disconnect switch interposed between the power source and said power cable;

a primary circuit for controlling said disconnect switch;

said disconnect switch comprising a disconnect switch coil for changing said disconnect switch from a closed position wherein the power source is connected to said power cable to an open position wherein the power source is disconnected from said power cable upon a threshold current flow through said disconnect switch coil;

a driver switch located in said primary circuit 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;

said resistor connected in said primary circuit for providing a reduced current flow through said disconnect switch coil below said threshold current required to open said disconnect switch; and

a secondary circuit interconnecting said second portion of said drain wire to driver switch for actuating said driver switch upon said secondary circuit sensing a leakage current from said drain wire to enable a threshold current to flow through said disconnect switch coil to open said disconnect switch for disconnecting said power cable from the power source.

17. A circuit for disconnecting a power source upon the detection of a leakage current, comprising:

a power cable comprising an insulated first wire and an insulated second wire;

said power cable having a conductive shield surrounding said insulated first wire and said insulated second wire;

a drain wire having a first and a second portion;

said first portion of said drain wire being non-insulated and in contact with said conductive shield;

an outer insulating layer molded about said conductive shield;

a disconnect switch interposed between the power source and said power cable;

a primary circuit for controlling said disconnect switch;

said disconnect switch comprising a disconnect switch coil for changing said disconnect switch from a closed position wherein the power source is connected to said power cable to an open position wherein the power source is disconnected from said power cable upon a threshold current flow through said disconnect switch coil;

a driver switch located in said primary circuit 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;

said resistor located in said primary circuit connected in series with said disconnect switch coil and in parallel with said driver switch for providing a reduced current flow through said disconnect switch coil below said threshold current required to open said disconnect switch; and

a secondary circuit interconnecting said second portion of said drain wire to driver switch for actuating said driver switch upon said secondary circuit sensing a leakage current from said drain wire to enable a threshold current to flow through said disconnect switch coil to open said disconnect switch for disconnecting said power cable from the power source.

18. A circuit for disconnecting a power source upon the detection of a leakage current, comprising:

a power cable comprising an insulated first wire and an insulated second wire;

said power cable having a conductive shield surrounding said insulated first wire and said insulated second wire;

a drain wire having a first and a second portion;

said first portion of said drain wire being non-insulated and in contact with said conductive shield;

an outer insulating layer molded about said conductive shield;

a disconnect switch interposed between the power source and said power cable;

a primary circuit for controlling said disconnect switch;

said disconnect switch comprising a disconnect switch coil for changing said disconnect switch from a closed position wherein the power source is connected to said power cable to an open position wherein the power source is disconnected from said power cable upon a threshold current flow through said disconnect switch coil;

a driver switch located in said primary circuit 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;

said resistor located in said primary circuit connected in series with said disconnect switch coil and in parallel with said driver switch for providing a reduced current flow through said disconnect switch coil below said threshold current required to open said disconnect switch; and

a secondary circuit interconnecting said second portion of said drain wire to driver switch for actuating said driver switch upon said secondary circuit sensing a leakage current from said drain wire to enable a threshold current to flow through said disconnect switch coil to open said disconnect switch for disconnecting said power cable from the power source.

19. A circuit for disconnecting a power source upon the detection of a leakage current, comprising:

a power cable comprising an insulated first wire and an insulated second wire;

said power cable having a conductive shield surrounding said insulated first wire and said insulated second wire;

said conductive shield comprises an organic conductive polymeric material;

a drain wire having a first and a second portion;

said first portion of said drain wire being non-insulated and in contact with said conductive shield;

an outer insulating layer molded about said conductive shield;

a disconnect switch interposed between the power source and said power cable;

said disconnect switch having a closed position wherein the power source is connected to said power cable and an open position wherein the power source is disconnected from said power cable; and

a circuit interconnecting said second portion of said drain wire to said disconnect switch for to opening said disconnect switch upon sensing a leakage current from said drain wire to disconnect said power cable from the power source.

20. A circuit for disconnecting a power source upon the detection of a leakage current, comprising:

a power cable comprising an insulated first wire and an insulated second wire;

said power cable having a conductive shield surrounding said insulated first wire and said insulated second wire;

said conductive shield comprises a conductive material;

a drain wire having a first and a second portion;

said first portion of said drain wire being non-insulated and in contact with said conductive shield;

an outer insulating layer molded about said conductive shield;

a disconnect switch interposed between the power source and said power cable;

said disconnect switch having a closed position wherein the power source is connected to said power cable and an open position wherein the power source is disconnected from said power cable; and

a circuit interconnecting said second portion of said drain wire to said disconnect switch for to opening said disconnect switch upon sensing a leakage current from said drain wire to disconnect said power cable from the power source.