GFCI with voltage level comparison and indirect sampling

• US 9,118,174 B2
• Filed: 03/14/2013
• Issued: 08/25/2015
• Est. Priority Date: 03/14/2013
• Status: Active Grant

• Current Assignee: Hubbell, Inc.
• Original Assignee: Hubbell, Inc.
• Inventors: Simonin, Stephen Paul
• Primary Examiner(s): BAUER, SCOTT ALLEN
• Application Number:
  US13/827,816
• Publication Number:
  US 20140268434A1
• Time in Patent Office: 894 Days
• Field of Search: 361/42
• US Class Current: 1/1
• CPC Class Codes: G01R 31/327 Testing of circuit interrupters, switches or circuit-breakers
• CPC Class Codes: H01H 83/04 with testing means for indicating the ability of the switch or relay to function properly
• CPC Class Codes: H01H 83/144 with differential transformer
• CPC Class Codes: H02H 1/0092 concerning the data processing means, e.g. expert systems, neural networks
• 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 3/162 for ac systems
• CPC Class Codes: H02H 3/33 using summation current transformers H02H3/347 takes precedence
• CPC Class Codes: H02H 3/335 the main function being self testing of the device
• CPC Class Codes: H02H 3/338 also responsive to wiring error, e.g. loss of neutral, break

Abstract

A circuit interrupting device having an auto-monitoring circuit for automatically testing various functions and structures of the device. The auto-monitoring circuit initiates an auto-monitoring routine which, among other things, establishes a self-test fault during either the positive or negative half-wave, or both, of an AC power cycle and determines whether the detection mechanisms within the device properly detect the self-test fault. An early detection signal indicates that the self-test fault was properly detected without interfering with the normal operation of the detection circuitry and without causing a false trip within the device. Additional functionality of the auto-monitoring circuit permits automatic verification that the device is properly wired, that is, not miswired, and determines whether the device has reached the end of its useful life.

Claims

1. A circuit interrupting device comprising:

one or more line terminals for connecting to an external power supply;

one or more load terminals for connecting to an external load;

an interrupting device connected to said line terminals and said load terminals and electrically connecting said line terminals to said load terminals when said circuit interrupting device is in a reset condition and disconnecting said line terminals from said load terminals when said circuit interrupting device is in a tripped condition;

a fault detection circuit that detects a fault condition in said circuit interrupting device and generates a fault detection signal when said fault condition is detected, wherein said fault detection signal is provided to said interrupting device to place said circuit interrupting device in said tripped condition;

an auto-monitoring circuit electrically coupled to said fault detection circuit and said interrupting device and continuously monitoring one or more signals to determine an operating state of said circuit interrupting device, wherein at least one of said monitored signals includes a first auto-monitoring input signal the value of which is at least partially determined by a value of a power indication signal generated by said fault detection circuit.

2. The circuit interrupting device recited in claim 1 wherein said fault detection circuit includes a GFCI device that detects a net current flowing from said line terminals to said load terminals and generates said fault detection signal when said net current exceeds a predetermined threshold.

3. The circuit interrupting device recited in claim 2 wherein said GFCI device receives a voltage input signal having a first value at a line input port and produces a voltage output signal having substantially the same value as said first value at a voltage output port.

4. The circuit interrupting device recited in claim 3 wherein said voltage input signal includes a rectified version of an alternating current (AC) power signal provided to said line terminals by said external power supply.

5. The circuit interrupting device recited in claim 4 further comprising a voltage conversion device that converts said voltage output signal to said first auto-monitoring input signal having a value different than the value of said voltage output signal.

6. The circuit interrupting device recited in claim 5, wherein said auto-monitoring circuit evaluates said first auto-monitoring input signal and determines that said fault detection circuit is inoperable and declares an end-of-life condition if the value of said first auto-monitoring input signal is below a first voltage level.

7. The circuit interrupting device recited in claim 1, further comprising a condition sensor that generates a condition signal, the value of said condition signal being determined based on whether the circuit interrupting device is in said reset condition or said tripped condition.

8. The circuit interrupting device recited in claim 7, wherein the value of said first auto-monitoring input signal is determined based on the value of said condition signal.

9. The circuit interrupting device recited in claim 8, wherein said auto-monitoring circuit determines that said circuit interrupting device is in said reset condition if said value of said first auto-monitoring input signal is greater than or equal to a first voltage level and less than a second voltage level, and said auto-monitoring circuit determines that said circuit interrupting device is in said tripped condition if said value of said first auto-monitoring input signal is greater than or equal to said second voltage level.

10. The circuit interrupting device recited in claim 8, further comprising a power supply circuit electrically connected to said line terminals and generating a direct current (DC) voltage signal based on a power signal provided by said external power supply, wherein said auto-monitoring circuit determines that said circuit interrupting device is in said reset condition when said value of said first auto-monitoring input signal is approximately equal to seventy-five percent of the value of said DC voltage signal, and said auto-monitoring circuit determines that said circuit interrupting device is in said tripped condition if said value of said first auto-monitoring input signal is approximately equal to the value of said DC voltage signal.

11. The circuit interrupting device recited in claim 1, further comprising a frequency determiner, wherein said external power supply includes an AC power supply that provides an AC input power signal at said line terminals and said frequency determiner determines the frequency of said input power signal based on said first auto-monitoring input signal.

12. The circuit interrupting device recited in claim 11, wherein said auto-monitoring circuit detects and counts zero-cross transitions of said first auto-monitoring input signal to determine whether said AC power input signal is stabilized to a predetermined frequency.

13. A circuit interrupting device comprising:

one or more line terminals for connecting to an external AC power supply;

one or more load terminals for connecting to an external AC load;

an interrupting device connected to said line terminals and said load terminals and delivering an AC power signal from said line terminals to said load terminals when said circuit interrupting device is in a reset condition and preventing said AC power signal from being delivered from said line terminals to said load terminals when said circuit interrupting device is in a tripped condition;

a fault detection circuit that detects a fault condition in said circuit interrupting device and generates a fault detection signal when said fault condition is detected, wherein said fault detection signal is provided to said interrupting device to place said circuit interrupting device in said tripped condition when said fault condition is detected;

an auto-monitoring circuit electrically coupled to said fault detection circuit and said interrupting device and said one or more line terminals, said auto-monitoring circuit including;

a DC power supply circuit coupled to said one or more line terminals and generating a DC voltage signal based on said AC power signal;

a programmable device programmed to repetitively run an auto-monitoring routine to regularly monitor one or more signals and determine an operating state of said circuit interrupting device based on respective values of said monitored signals; and

a first switching device controlled by said programmable device for controllably providing a self-test fault signal to said fault detection circuit,

wherein said programmable device of said auto-monitoring circuit receives a test signal from said fault detection circuit on a first signal input port and determines that said fault detection circuit is adequately powered if the value of said test signal is greater than or equal to about one half the value of said DC voltage signal.

14. The circuit interrupting device recited in claim 13 wherein said auto-monitoring circuit further includes a condition sensing device coupled to said programmable device and said programmable device determines whether said circuit interrupting device is in said reset condition or said tripped condition based on the value of a condition signal generated by said condition sensing device.

15. The circuit interrupting device recited in claim 14, wherein said condition signal and said test signal are combined and delivered to said first signal input port and said programmable device controllably generates an end-of-life trip signal to ensure said circuit interrupting device is in said tripped state based on the value of said combined signal.

16. A method of monitoring the operational state of an electrical wiring device the method comprising the steps of:

receiving an AC power signal power signal;

generating a DC power signal by rectifying said AC power signal;

running an auto-monitoring program stored in a programmable circuit device;

monitoring a test signal output from a fault detection circuit to determine an operational state of said electrical wiring device;

determining, in said programmable circuit device, an end-of-life state if said test signal from said fault detection circuit is less than a threshold value;

generating an alarm signal when said end-of-life state is determined; and

determining, in said programmable circuit device, a frequency associated with said AC power signal based on an evaluation of said test signal.

17. The method recited in claim 16, further comprising the steps of:

monitoring an output signal from a contacts sensing device; and

determining, in said programmable circuit device, whether said electrical wiring device is in a tripped state in which said AC power signal is prevented from being delivered to a load, or in a reset state in which said AC power signal is delivered to said load based on said output signal from said contacts sensing device.

18. The method recited in claim 17, further comprising the steps of:

delaying said auto-monitoring program if said frequency associated with said AC power signal is not stable; and

incrementing a fail tally if said frequency associated with said AC power signal does not stabilize to within a predetermined range of frequencies within a predetermined period of time.

19. The method recited in claim 17, wherein said steps of determining an end-of-life state, determining whether said electrical wiring device is in a tripped state or in a reset state, and determining a frequency associated with said AC power signal are performed by said programmable circuit device by evaluating a combined signal generated by combining said test signal from said fault detection circuit and said output signal from said contacts sensing device.

20. The method as recited in claim 16, further comprising the steps of:

activating, with said programmable device, respective trigger signals of at least two back-up switching devices for placing said electrical wiring device in said tripped state, wherein none of said back-up switching devices is electrically connected to said fault detection circuit.