Protective device for an electrical supply facility

Patent metadata

Field	Value
Publication number	US-9948087-B2
Application number	US-201313793135-A
Country	US
Kind code	B2
Filing date	Mar 11, 2013
Priority date	Mar 8, 2010
Publication date	Apr 17, 2018
Grant date	Apr 17, 2018

Abstract

The present invention is directed to a protective device configured to be coupled between an AC power source and an electrical load. A ground continuity monitor is coupled to the ground conductor, the ground continuity monitor being configured to detect a ground discontinuity condition in the ground conductor. A circuit interrupter mechanism is configured to interrupt electrical continuity in a tripped state and establish electrical continuity in a reset state. A self-test circuit is coupled to the ground continuity monitor and configured to perform a simulated ground continuity test that simulates the ground discontinuity condition. The self-test circuit provides a test failure signal when the ground continuity monitor fails to provide an output signal in response to the simulated ground continuity test. The test failure signal is configured to trip the circuit interrupter mechanism.

First claim

What is claimed is:

1. A protective device configured to be coupled between an AC power source and an electrical load, the AC power source including at least one hot conductor and a ground conductor connected to earth ground, the device comprising:
an input device configured to be coupled to the AC power source, the input device comprising a plurality of line contacts including at least one hot line contact configured to be coupled to the at least one hot conductor and a line-side ground contact configured to be coupled to the ground conductor;
an output device including a plurality of load contacts configured to be coupled to the electrical load, the plurality of load contacts including at least one hot load contact and a load-side ground contact, the output device being configured to provide the electrical load with AC electric power received via the input device from the AC power source;
a ground continuity monitor coupled to the ground conductor, the ground continuity monitor being configured to detect a ground discontinuity condition in the ground conductor, wherein the ground conductor is substantially isolated from the electrical load during at least one period of time during which the ground continuity monitor is configured to detect a ground discontinuity, the ground conductor being subsequently connected to the electrical load upon failing to detect a ground discontinuity during the at least one period of time;
a circuit interrupter mechanism coupled to the ground continuity monitor, the circuit interrupter mechanism being configured to interrupt electrical continuity between the at least one hot line contact and the at least one hot load contact in a tripped state and establish electrical continuity between the at least one hot line contact and the at least one hot load contact in a reset state; and
a self-test circuit coupled to the ground continuity monitor and configured to perform a simulated ground continuity test that simulates the ground discontinuity condition, the self-test circuit providing a test failure signal when the ground continuity monitor fails to provide an output signal in response to the simulated ground continuity test, the circuit interrupter mechanism being configured to trip in response to the test failure signal.

2. The device of claim 1 , wherein the simulated ground continuity test is performed from time-to-time when the circuit interrupter mechanism is in the reset state and the source of electrical power is coupled to the electrical load.

3. The device of claim 1 , wherein the ground continuity monitor detects the ground discontinuity condition by propagating both a continuous test current and a recurring test current through the ground conductor.

4. The device of claim 1 , further including a conditioning circuit configured to propagate a conditioning signal via the ground conductor in response to a ground fault condition, the ground continuity monitor being disabled by the self-test circuit to prevent the ground continuity monitor from interpreting the conditioning signal as the ground discontinuity condition.

5. The device of claim 4 , wherein the conditioning signal includes a signal component that is proportional to a ground fault current or a simulated ground fault current.

6. The device of claim 4 , wherein the conditioning signal includes a signal component that is configured to substantially null a current component being propagated in the ground conductor.

7. The device of claim 6 , wherein the plurality of line contacts includes a neutral conductor coupled to the AC power source, the current component being a function of a voltage drop in the neutral conductor.

8. The device of claim 4 , wherein the conditioning signal is propagated at a time when the simulated ground continuity test is not being performed.

9. The device of claim 4 , wherein the self-test circuit performs a test configured to determine whether the conditioning circuit is in an end-of-life state.

10. The device of claim 4 , further comprising a ground fault detector configured to detect a ground fault condition via an output signal provided by the conditioning circuit.

11. The device of claim 10 , wherein the self-test circuit is configured to conduct a simulated ground fault test or a simulated grounded neutral test and provide an end-of-life alarm if the ground fault detector fails to respond to the self-test within a predetermined period of time or within a predetermined number of self-test attempts.

12. The device of claim 10 , wherein the ground fault condition is sensed by monitoring a differential signal.

13. The device of claim 1 , further comprising at least one electrical test contact coupled to the circuit interrupter mechanism, the self-test circuit being configured to detect a welded contact condition in the circuit interrupter mechanism when there is not a predetermined voltage between the at least one electrical test contact and a reference potential when the circuit interrupter is in the tripped state.

14. The device of claim 13 , wherein the at least one test contact includes a set of test contacts, one test contact of the set of test contacts being at the reference potential.

15. The device of claim 1 , wherein the circuit interrupter includes a set of electrical interrupting contacts between the plurality of line contacts and the plurality of load contacts, the set of electrical contacts include a hot interrupting contact arrangement between a hot line contact and a hot load contact and a neutral interrupting contact arrangement between a neutral line contact and a neutral load contact, and wherein the device further comprises a first set of electrical test contacts coupled to the hot interrupting contact arrangement and a second set of electrical test contacts coupled to the neutral interrupting contact arrangement.

16. The device of claim 15 , wherein the self-test circuit is configured to interrogate a contact of the first set of electrical contacts to determine if the hot interrupting contact arrangement is welded.

17. The device of claim 16 , wherein the self-test circuit is configured to monitor a voltage between the first set of electrical contacts and the second set of electrical contacts for the presence of a weld indication voltage.

18. The device of claim 16 , wherein the first set of electrical test contacts are coupled to the line hot conductor in the tripped state if the hot contact arrangement is not welded.

19. The device of claim 15 , wherein the self-test circuit is configured to interrogate a contact of the second set of electrical contacts to determine if the neutral interrupting contact arrangement is welded.

20. The device of claim 19 , wherein the self-test circuit is configured to monitor the second set of electrical contacts for the presence of a weld indication voltage therebetween.

21. The device of claim 20 , wherein the second set of electrical test contacts are coupled to the line neutral contact in the tripped state if the neutral contact arrangement is not welded.

22. The device of claim 1 , wherein the self-test circuit permits the circuit interrupter to enter the reset state when an end of life condition is not detected.

23. The device of claim 1 , wherein the self-test circuit is configured to detect that at least a portion of circuit interrupter mechanism is welded without the circuit interrupter mechanism being in a tripped state.

24. The device of claim 1 , wherein the self-tes

Assignees

• Pass & Seymour Inc

Inventors

• Haines Joshua Paul
• Morgan Kent R
• Mueller Brian

Classifications

• G01R31/52

  Testing for short-circuits, leakage current or ground faults · CPC title

• G01R31/3277

  of low voltage devices, e.g. domestic or industrial devices, such as motor protections, relays, rotation switches · CPC title

• H02H3/16

  responsive to fault current to earth, frame or mass (with balanced or differential arrangement H02H3/26 {; monitoring earth connection H02H5/105}) · CPC title

• H02H5/105

  responsive to deterioration or interruption of earth connection (for preventing switching-on H02H11/001) · CPC title

• H02H3/162 Primary

  for AC systems · CPC title