Fault indicator having delayed trip circuit

• US 4,795,982 A
• Filed: 04/24/1987
• Issued: 01/03/1989
• Est. Priority Date: 04/24/1987
• Status: Expired due to Term

• Current Assignee: Edmund O. Schweitzer III, Jean E. Schweitzer, Marilyn L. Schweitzer
• Original Assignee: Edmund O. Schweitzer Jr
• Inventors: Schweitzer, Edmund O. Jr.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US07/042,282
• Time in Patent Office: 620 Days
• Field of Search: 324/146, 324/133, 324/508, 324/512, 324/522, 324/524, 324/555, 324/543, 324/126, 340/660, 340/662, 340/664, 361/93, 361/94, 361/110, 361/71, 361/75
• US Class Current: 324/508
• CPC Class Codes: G01R 31/08 Locating faults in cables, transmission lines, or networks

Abstract

A reset coordinated fault indicator for indicating the occurrence of a fault current in a monitored conductor includes an electrically actuated indicator flag. A trip circuit within the fault indicator impulses the indicator flag from a normal reset-indicating state to a fault-indicating state following the occurrence of a fault current in the conductor. A reset circuit periodically impulses the indicator flag to the reset-indicating state upon restoration of power to the conductor. To preclude simultaneous actuation of the trip and reset circuits and consequent failure of the indicator flag to register a fault, the trip circuit, upon the occurrence of a fault, first actuates the reset circuit to render the reset circuit inoperative, and then actuates the indicator flag to provide a fault indication.

Claims

1. A fault indicator for indicating the occurrence of a fault current in a monitored electrical conductor of an alternating current power distribution system, comprising:

status indicating means having a reset-indicating state and a fault-indicating state;

trip circuit means for conditioning said status indicating means to said fault-indicating state in response to the occurrence of a fault current in the conductor;

reset circuit means periodically operable for a predetermined reset period for conditioning said status indicating means to said reset-indicating state, and inoperable for a predetermined recovery period following each such reset period; and

said trip circuit means rendering said reset circuit means initially operable upon occurrence of a fault, and conditioning said status indicating means to said fault-indicating state during said recovery period following a trip delay per greater than said predetermined reset period to preclude simultaneous operation of said trip and reset circuits.

2. A fault indicator as defined in claim 1 wherein said reset circuit means include a reset capacitor for supplying operating current thereto, and a discharge circuit operable in conjunction with said reset capacitor for establishing said predetermined reset peiod.

3. A fault indicator as defined in claim 2 wherein said reset capacitor is capacitively coupled to the monitored electrical conductor.

4. A fault indicator as defined in claim 3 wherein said trip circuit means include switch means responsive to the occurrence of a fault in the monitored conductor, and said reset circuit means are responsive to the closure of said switch means for initiating said reset period.

5. A fault indicator as defined in claim 4 wherein said switch means comprise a reed switch in magnetic communication with the monitored conductor.

6. A fault indicator as defined in claim 2 wherein said reset circuit means include a charging circuit for said reset capacitor, said charging circuit forming in conjunction with said reset capacitor an RC timing circuit for establishing said recovery period.

7. A fault indicator as defined in claim 6 wherein wherein said recovery period is substantially greater than said reset period.

8. A fault indicator as defined in claim 1 including a trip coordination circuit for inhibiting said trip circuit for a predetermined coordination period following initial power-up of the monitored conductor.

9. A fault indicator as defined in claim 8 wherein the operation of said coordination circuit is substantially independent of the operation of said reset circuit.

10. A fault indicator as defined in claim 1 wherein said trip circuit means include a trip capacitor for powering said trip circuit, and an RC timing circuit operative in conjunction with said trip capacitor for establishing said trip delay period.

11. A fault indicator as defined in claim 10 wherein said trip capacitor is capacitively coupled to the monitored electrical conductor.

12. A fault indicator for indicating the occurrence of a fault current in a monitored electrical conductor of an alternating current power distribution system, comprising:

status indicating means having a reset-indicating state and a fault-indicating state;

reset circuit means periodically operable for a predetermined reset period for conditioning said status indicating means to said reset-indicating state, and inoperative for a predetermined recovery period following each such reset period, said reset circuit means including a reset capacitor for supplying operating current thereto, a discharge circuit operable in conjunction with said reset capacitor for establishing said reset period, and a charging circuit operable in conjunction with said reset capacitor for establishing said recovery period; and

trip circuit means for rendering said reset circuit operable, and including a trip capacitor and an associated RC time constant circuit for conditioning said status indicating means to said fault-indicating state during said recovery period after a predetermined trip delay period greater than said reset period, in response to the occurrence of a fault current in the monitored conductor, whereby simultaneous conditioning of said indicating means by said reset and trip circuit means is prevented.

13. A fault indicator as defined in claim 12 wherein said reset and trip capacitors are capacitively coupled to the monitored electrical conductor.

14. A fault indicator as defined in claim 12 wherein said recovery period is substantially greater than said reset period.

15. A fault indicator as defined in claim 12 wherein said trip circuit means include switch means responsive to the occurrence of a fault in the monitored conductor, and said reset circuit means are responsive to the closure of said switch means for initiating said reset period.

16. A fault indicator as defined in claim 15 wherein said switch means comprise a reed switch in magnetic communication with the monitored conductor.

17. A fault indicator as defined in claim 12 including a trip coordination circuit for inhibiting said trip circuit for a predetermined coordination period following initial power-up of the monitored conductor.

18. A fault indicator as defined in claim 17 wherein the operation of said coordination circuit is substantially independent of the operation of said reset circuit.

19. A fault indicator as defined in claim 12 wherein said recovery period is substantially greater than said reset period.