Arcing fault detector

• US 5,121,282 A
• Filed: 03/30/1990
• Issued: 06/09/1992
• Est. Priority Date: 03/30/1990
• Status: Expired due to Term

• Current Assignee: Square D Company (Schneider Electric SE)
• Original Assignee: Orval C. White
• Inventors: White, Orval C.
• Primary Examiner(s): DEBOER, TODD
• Application Number:
  US07/502,042
• Time in Patent Office: 802 Days
• Field of Search: 361/45, 361/49, 361/42, 361/85-87, 361/79, 361/91, 361/111
• US Class Current: 361/42
• CPC Class Codes: G01R 31/1263 of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation
• CPC Class Codes: G01R 31/1272 of cable, line or wire insulation, e.g. using partial discharge measurements locating faults in cables G01R31/083
• CPC Class Codes: G01R 31/14 Circuits therefor , e.g. for generating test voltages, sensing circuits G01R31/1209 - G01R31/1227 take precedence; for testing switches G01R31/327
• CPC Class Codes: H02H 1/0015 Using arc detectors

Abstract

An arcing fault detector is set up to identify arcing faults and to distinguish them from other disturbances in a circuit. A plurality of electrical conditions are monitored and the conditions are tested against predetermined parameters for establishing a series of logical conditions relating to the presence of an arcing fault. A logic circuit combines the logical conditions for deciding on the presence of an arcing fault. An output signal of the logic circuit is used to activate a relay for interrupting the supply of electrical power to the circuit.

Claims

1. An arcing fault detector for protecting household, business, and industrial electrical circuits comprising:

a current transformer that produces a signal for tracking the behavior of current in the electrical circuit;

a voltage divider that produces a signal for tracking the behavior of voltage in the electrical circuit;

a plurality of processing circuits that isolates individual electrical characteristics apparent from the current and voltage tracking signals and that tests the individual electrical characteristics against predetermined parameters bearing respective logical relationships to the presence of an arcing fault in the electrical circuit;

comparators within each of said processing circuits that register the outcome of the tested electrical characteristics as logical condition signals;

a logic circuit that combines the logical condition signals and that produces an output signal which registers not less than all actual arcing faults that fulfill any one of the logical conditions and not more than all non-fault disturbances that fulfill any one other of the logical conditions; and

means for interrupting electrical power to the electrical circuit in response to a logical state of the output signal.

2. The arcing fault detector of claim 1 wherein the test parameters define each of the respective logical relationships as one of a nonexclusive condition, a noninclusive condition, and a nonexclusive-noninclusive condition.

3. The arcing fault detector of claim 2 wherein said logic circuit combines two nonexclusive conditions with a logical "and".

4. The arcing fault detector of claim 3 wherein the output signal of the logic circuit registers less than all non-fault disturbances that fulfill any one of the nonexclusive conditions.

5. The arcing fault detector of claim 2 wherein said logic circuit combines two noninclusive conditions with a logical "or".

6. The arcing fault detector of claim 5 wherein the output signal of the logic circuit register-s-more than all actual arcing faults that fulfill any one of the noninclusive conditions.

7. The arcing fault detector of claim 2 wherein said logic circuit combines a nonexclusive-noninclusive condition and one of a nonexclusive condition and another nonexclusive-noninclusive condition with a logical "and" for defining an effective noninclusive condition.

8. The arcing fault detector of claim 7 wherein said logic circuit also combines said effective noninclusive condition and a noninclusive condition with a logical "or".

9. The arcing fault detector of claim 8 wherein the output signal of the logic circuit registers more than all actual arcing faults that fulfill any one of the noninclusive and nonexclusive-noninclusive conditions.

10. The arcing fault detector of claim 2 wherein said logic circuit combines a nonexclusive-noninclusive condition and one of a noninclusive condition and another nonexclusive-noninclusive condition with a logical "or" for defining an effective nonexclusive condition.

11. The arcing fault detector of claim 10 wherein said logic circuit also combines said effective nonexclusive condition and a nonexclusive condition with a logical "and".

12. The arcing fault detector of claim 11 wherein the output signal of the logic circuit registers less than all non-fault disturbances that fulfill any one of the nonexclusive and nonexclusive-noninclusive conditions.

13. The arcing fault detector of claim 1 wherein one of said plurality of processing circuits provides for testing for a reduced power factor in the range of power factors associated with arcing faults.

14. The arcing fault detector of claim 13 wherein one of said comparators registers the outcome of the test for a reduced power factor as a noninclusive condition.

15. The arcing fault detector of claim 1 wherein one of said plurality of processing circuits provides for testing for a reduced voltage in the timed vicinity of the usual occurrence of a peak voltage.

16. The arcing fault detector of claim 15 wherein one of said comparators registers the outcome of the test for a reduced voltage as a noninclusive-noninclusive condition.

17. The arcing fault detector of claim 1 wherein one of said plurality of processing circuits provides for testing for a high frequency current disturbance of the type produced by a DC current component of an arcing fault current.

18. The arcing fault detector of claim 17 wherein one of said comparators registers the outcome of the test for a high frequency current disturbance as a nonexclusive condition.

19. An arcing fault detector for an electrical circuit comprising:

a current transformer for producing a signal tracking the behavior of current in the electrical circuit;

a voltage divider for producing a signal tracking the behavior of voltage in the electrical circuit;

a first timer for comparing a phase relationship between the voltage tracking signal and current tracking signal;

second timer for identifying a timed interval in the vicinity of the usual peak voltage of the voltage tracking signal;

a comparator for identifying a reduced voltage within the timed interval with respect to the usual peak voltage;

a high pass filter for identifying the an occurrence of a high frequency disturbance in the current tracking signal; and

a logic circuit for combining conditions relating to (a) the phase relationship between the voltage tracking signal and current tracking signal, (b) the voltage within the timed interval, and (c) the frequency of disturbance in the current tracking signal, and for producing an output signal indicating the presence of an arcing fault in the electrical circuit.

20. The arcing fault detector of claim 19 further comprising a relay for interrupting a supply of power to the electrical circuit.

21. The arcing fault detector of claim 19 wherein the phase relationship is used to identify low power factors associated with arcing faults.

22. The arcing fault detector of claim 19 wherein the voltage within the timed interval is used to identify reduced voltages required to sustain current flow across an arcing fault gap.

23. The arcing fault detector of claim 19 wherein the frequency disturbance in the current tracking signal is used to identify DC current components associated with arcing faults.

24. An arcing fault detector for interrupting the supply of electrical power to a circuit comprising:

means for producing a signal tracking the behavior of current in the circuit;

means for producing a signal tracking the behavior of voltage in the circuit;

means for processing at least one of the signals tracking the respective behaviors of current and voltage in the circuit, and for identifying a first electrical characteristic bearing a logical relationship to the presence of an arcing fault in the circuit as one of a nonexclusive condition, a noninclusive condition, and a nonexclusive-noninclusive condition;

means for processing at least the other of the signals tracking the respective behaviors of current and voltage in the circuit, and for identifying a second electrical characteristic bearing a logical relationship to the presence of an arcing fault in the circuit as one of a nonexclusive condition, a noninclusive condition, and a nonexclusive-noninclusive condition;

means for producing a logical output signal by logically combining the one of the logical conditions relating to the first electrical characteristic with the one of the logical conditions relating to the second electrical characteristic according to one of the following rules wherein;

two nonexclusive conditions are combined with a logical "and",

two noninclusive conditions are combined with a logical "or",

a nonexclusive-noninclusive condition and one of a nonexclusive condition and another nonexclusive-noninclusive condition are combined by a logical "and" defining an effective noninclusive condition, and

a nonexclusive-noninclusive condition and one of a noninclusive condition and another nonexclusive-noninclusive condition are combined by a logical "or" defining an effective nonexclusive condition; and

means for interrupting the supply of electrical power to the circuit in response to a logical state of the output signal.

25. The arcing fault detector of claim 24 wherein said logical output means combines two nonexclusive conditions with a logical "and".

26. The arcing fault detector of claim 24 wherein said logical output means combines two noninclusive conditions with a logical "or".

27. The arcing fault detector of claim 24 including further means for processing both of the signals tracking the respective behaviors of current and voltage in the circuit, and for identifying a third electrical characteristic bearing a logical relationship to the presence of an arcing fault in the circuit as one of a nonexclusive condition, a noninclusive condition, and a nonexclusive-noninclusive condition.

28. The arcing fault detector of claim 27 wherein said logical output means combines a nonexclusive-noninclusive condition and one of a nonexclusive condition and another nonexclusive-noninclusive condition with a logical "and" for defining an effective noninclusive condition.

29. The arcing fault detector of claim 28 wherein said logical output means also combines said effective noninclusive condition and a noninclusive condition with a logical "or".

30. The arcing fault detector of claim 27 wherein said logical output means combines a nonexclusive-noninclusive condition and one of a noninclusive condition and another nonexclusive-noninclusive condition with a logical "or" for defining an effective nonexclusive condition.

31. The arcing fault detector of claim 29 wherein said logical output means also combines said effective nonexclusive condition and a nonexclusive condition with a logical "and".