Power line testing device with signal generator and signal detector

• US 20020039026A1
• Filed: 04/04/2001
• Published: 04/04/2002
• Est. Priority Date: 04/04/2000
• Status: Active Grant

• Current Assignee: Contact Technology Systems, Inc.
• Original Assignee: Contact Technology Systems, Inc.
• Inventors: Wottrich, Joachim, Stroth, Peter, Stroth, John E.
• Granted Patent: US 6,466,029 B2
• Time in Patent Office: Days
• US Class Current: 324/509
• CPC Class Codes: G01R 31/3277 of low voltage devices, e.g. domestic or industrial devices, such as motor protections, relays, rotation switches

Abstract

A power line testing device with signal generator and signal detector incorporates a DC power supply that is capable of generating DC power from a miswired outlet, as long as there is a hot conductor and a return path. The device includes a signal generator which generates a signal that is easily distinguishable from noise. The transmitter further includes a spark gap for creating an arc used to test the function of an ACFI device connected to the branch under test. The transmitter further detects the integrity of circuit ground by measuring its impedance. A receiver of the device measures the elapsed time of the testing signals, permitting a more sophisticated test of interrupter device function.

Claims

1. A transmitter for placing an identification signal on an AC power distribution circuit, comprising:

at least first and second output terminals for connection to different ones of a plurality of conductors of the power distribution circuit, and

a signal generator coupled to the first and second output terminals, the signal generator superimposing an identification signal on an alternating current carrier signal, the identification signal having a repetition period different from the period of the carrier signal.

2. The transmitter of claim 1, wherein the identification signal has both positive-going and negative-going components.

3. The transmitter of claim 1, wherein the identification signal repeats for a first predetermined number of carrier cycles and then does not repeat for a second predetermined number of carrier cycles.

4. The transmitter of claim 1, wherein the identification signal includes at least one signal frequency substantially different from the frequency of the carrier signal.

5. The transmitter of claim 1, wherein the transmitter has first, second and third terminals connectable to hot, neutral and ground terminals of an outlet, the transmitter actuable to transmit the identification signal on any two of the terminals so long as an AC voltage occurs between said any two of the terminals.

6. The transmitter of claim 1, and further comprising a transformerless power supply connectable to hot, neutral and ground terminals of an outlet, the power supply having a power output coupled to a power input of the signal generator, the power supply producing power on the power output when connected to the hot, neutral and ground terminals of the outlet even where the outlet terminals have been miswired, as long as one of the outlet terminals is at a hot voltage and another of the outlet terminals is connected to a return path.

7. An electrical wiring testing device for testing whether hot, neutral and ground conductors have been correctly connected to respective hot, neutral and ground terminals of an AC power outlet, comprising:

hot, neutral and ground terminals for plugging into hot, neutral and ground receptacles of an AC power outlet;

a sensing, circuit coupled to the hot, neutral and ground terminals of the device for sensing one of a plurality of wiring conditions recognizable by the sensing circuit, the conditions including a correct wiring condition and a reversed hot and neutral wiling condition; and

indicator circuitry coupled to the sensing circuit for indicating which of the wiling conditions is present.

8. The electrical wiring testing device of claim 7, wherein the wiring conditions recognizable by the wiring circuit further including open ground, open neutral, reversed hot and ground, hot connected to neutral and neutral conductor not connected, two hot conductors connected respectively to neutral and ground, and two hot conductors connected to hot and ground.

9. A transformerless power supply for supplying DC power, comprising:

hot, neutral and ground input terminals for respective connection to hot, neutral and ground terminals of an AC power outlet;

an AC/DC conversion circuit having a DC power output and an input; and

a hot and return path conductor recognition circuit interposed between the hot, neutral and ground input terminals and the input of the conversion circuit and supply ground, the recognition circuit supplying power to the input of the conversion circuit even where the AC power outlet has been miswired, as long as one of the terminals of the AC power outlet is connected to a hot conductor and another of the terminals of the AC power outlet is connected to a return path.

10. The transformerless power supply of claim 9, wherein the recognition circuit comprises first, second and third diode bridge circuits, outputs of each of the diode bridge circuits coupled to the input of the conversion circuit, a first input of the first and second diode bridge circuits coupled to the hot input terminal, a second input of the first diode bridge circuit and a first input of the third diode bridge circuit coupled to the neutral input terminal, a second input of the second diode bridge circuit and a second input of the third diode bridge circuit coupled to the ground input terminal.

11. The transformerless power supply of claim 9, wherein the AC/DC conversion circuit comprises a voltage regulator.

13. The AC power branch circuit testing device of claim 12, wherein the ground terminal is connected to a ground receptacle of the AC power outlet.

16. The AC power branch circuit locator device of claim 15, wherein the receiver further includes a signal strength detector, a memory and a comparator, the receiver moveable to be positioned adjacent each of a plurality of AC power distribution circuits including the first AC power distribution circuit, the memory storing a highest signal strength, the comparator coupled to the memory and comparing a currently sensed identification signal strength with a stored, highest identification signal strength and indicating whether a closest adjacent one of the AC power distribution circuits is emitting a signal of at least said highest signal strength, thereby identifying the first AC power distribution circuit.

17. The AC power branch circuit locator device of claim 15, wherein the receiver further includes an signal strength indicator which gives an indication of signal strength which varies according to the magnitude of the sensed signal strength.

18. The AC power branch circuit locator device of claim 17, wherein the signal strength indicator includes an audible indicator emitting an audio frequency which varies in pitch according to detected signal strength.

19. The AC power branch circuit locator device of claim 15, and further comprising a third output terminal for connection to a third conductor of the first power distribution circuit, an energization sensor coupled to the first, second and third terminals to determine which ones of the conductors connected thereto is energized, the transmitter transmitting an identification signal on any available energized one of the conductors regardless of whether the conductors have been miswired, as long as another one of the conductors provides a return path.

12. An AC power branch circuit testing device, comprising:

hot, neutral and ground terminals respectively connectable to a hot receptacle, a neutral receptacle and a grounding point of an AC power outlet;

a ground integrity circuit coupled to the ground terminal and detecting whether a parasitic resistance of the connection between the grounding point and ground exceeds a predetermined maximum; and

an indicator coupled to the ground integrity circuit for indicating whether the detected parasitic resistance exceeds the predetermined maximum.

14. A ground integrity testing device, comprising:

a generator circuit having an output for generating a signal at a predetermined frequency;

a sensing circuit coupled between a voltage supply and a grounding point to be tested;

a coupling circuit coupling the generator circuit with the sensing circuit for transmitting the second signal of the predetermined frequency to the sensing circuit, any parasitic impedance connected between the sensing circuit grounding point and ground causing a phase shift to the second signal;

a detection circuit coupled to the sensing circuit for detecting the phase shift of the second signal; and

an indicator coupled to the detection circuit and indicating a ground integrity problem if the phase shift exceeds a predetermined amount.

15. An AC power branch circuit locator device, comprising:

a transmitter for placing an identification signal on a first AC power distribution circuit, at least first and second output terminals for connection to different ones of a plurality of conductors of the first power distribution circuit, a signal generator superimposing an identification signal on an alternating current carrier signal, the identification signal having a repetition period different from the period of the carrier signal; and

a receiver for use in a location remote from the transmitter but in proximity to the first AC power distribution circuit, the receiver operable to detect the identification signal.

20. A receiver for use in locating a first AC power branch circuit, comprising:

A sensing circuit for detecting, in a proximate one of a plurality of AC power branch circuits including the first AC power branch circuit, an identification signal, the identification signal being strongest on the first AC power branch circuit;

a memory coupled to the sensing circuit for storing a strength of the detected identification signal; and

a comparator coupled to the memory for comparing the strength of a currently sensed identification signal to a stored identification signal; and

an indicator coupled to the comparator and providing an indication to the user that a currently sensed identification signal has a strength which is at least as great as that of the stored identification signal, thereby permitting the user to identify the first AC power branch circuit.

21. The receiver of claim 20, wherein the comparator comprises a programmed microcontroller.

22. A receiver for use in locating a first AC power branch circuit, comprising:

A sensing circuit for detecting, in a proximate one of a plurality of AC power branch circuits including the first AC power branch circuit, an identification signal, the identification signal being strongest on the first AC power branch circuit; and

A signal strength indicator coupled to the sensing circuit and giving and indication of signal strength which varies according to the magnitude off the sensed signal strength.

23. The receiver of claim 22, wherein the signal strength indicator includes an audible indicator emitting a audio frequency which varies in pitch according to detected signal strength.

26. The fault interrupter testing device of claim 25, wherein the timer, sensor and comparator include a programmed microcontroller.

28. The method of claim 27, and further comprising the steps of:

imposing identification signal portions on selected ones of a plurality of adjacent carrier signal half-cycles; and

not imposing identification signal portions on the remainder of said plurality of adjacent carrier signal half-cycles.

24. A transmitter for an AC power branch circuit testing device connectable to HOT, NEUTRAL and GROUND conductors of an AC power branch circuit, comprising:

a wiring scenario analyzer of the transmitter detecting which of the conductors are energized and which provide a return path, an indicator circuit of the transmitter coupled to the wiring scenario analyzer to uniquely indicate which of a plurality of wiring scenarios is present;

a ground integrity testing circuit of the transmitter coupled to the GROUND conductor of the power branch circuit and measuring a preselected one of a parasitic resistance or a parasitic impedance of the ground connection, the indicator circuit of the transmitter coupled to the ground integrity testing circuit for indicating whether or not to the ground connection is of sufficient integrity;

a ground fault testing circuit coupled to the GROUND conductor and an energized one of the other conductors of the AC power branch circuit and operable to simulate a ground fault on the AC power branch circuit;

an arc fault testing circuit coupled between the HOT and NEUTRAL conductors of the AC power branch circuit and operable to simulate an arc fault on the AC power branch circuit; and

a signal generator for generating an identification signal on an energized one of the conductors of the AC power branch circuit for detection by a receiver positioned proximate to the AC power branch circuit but remote from the transmitter.

25. A fault interrupter testing device, comprising:

A user-actuable switch for creating a fault signal across a selected two of a plurality of conductors of an AC power branch circuit, the AC power branch circuit having connected thereto a fault interrupter;

a sensor coupled to the selected two of the plurality of conductors for sensing the fault signal;

a timer coupled to the sensor for timing the duration of the fault signal;

a comparator coupled to the timer for periodically comparing the duration of the fault signal to a predetermined stored value; and

an indicator coupled to the comparator and responsive to the comparator sensing that the duration has exceeded the stored value for indicating that the fault interrupter has not tripped the circuit within a time equal to the predetermined stored value.

27. A method for transmitting an identification signal across an AC power distribution circuit, comprising the steps of:

identifying an energized conductor and a return path conductor of an AC power distribution circuit, the energized conductor carrying an AC carrier signal; and

superimposing an identification signal on the AC carrier signal such that a period of repetition of the identification signal is greater than a period of the AC carrier signal.

29. A method for determining the integrity of a ground connection in an AC power distribution circuit, comprising the steps of:

connecting a ground integrity circuit to a GROUND terminal of the AC power distribution circuit;

using the ground integrity circuit, measuring the parasitic resistance between the GROUND terminal and earth ground; and

using an indicator circuit coupled to the ground integrity circuit to indicate whether the measured parasitic resistance exceeds a predetermined maximum.

30. A method for determining the integrity of a ground connection in an AC power distribution circuit, comprising the steps of:

connecting a ground integrity circuit to a GROUND terminal of the AC power distribution circuit;

generating a varying signal on the AC power distribution circuit;

using the ground integrity circuit, measuring a parasitic impedance between the GROUND terminal and earth ground by measuring a phase shift of the varying signal; and

using an indicator circuit coupled to the ground integrity circuit to indicate whether the measured parasitic impedance exceeds a predetermined maximum.

31. A method of distinguishing a first AC power distribution circuit from others of a plurality of AC power distribution circuits including the first AC power distribution circuit, comprising the steps of:

generating an identification signal on the first AC power distribution circuit from a first location;

at a second location remote from the first location, moving a mobile receiver to be adjacent a selected one of the plurality of AC power distribution circuits;

detecting a signal strength of the identification signal in the selected one of the AC power distribution circuits;

storing the detected signal strength;

moving the mobile receiver to be adjacent a second selected one of the plurality of AC power distribution circuits;

detecting a second signal strength of the identification signal as present in the second selected one of the AC power distribution circuits;

comparing the second signal strength to the stored signal strength;

if the second signal strength is greater than or equal to the stored signal strength, giving an indication thereof to a user;

if the second signal strength is greater than or equal to the stored signal strength, replacing the stored signal strength with the second signal strength; and

repeating said steps of detecting, comparing, indicating and replacing until the first AC power distribution circuit is identified.