Microprocessor controlled fault detector with circuit overload condition detection

• US 6,822,576 B1
• Filed: 10/25/2002
• Issued: 11/23/2004
• Est. Priority Date: 10/26/2001
• Status: Expired due to Term

• Current Assignee: Schweitzer Engineering Laboratories, Incorporated
• Original Assignee: E.O. Schweitzer Manufacturing Compay, LLC (Schweitzer Engineering Laboratories, Incorporated)
• Inventors: Feight, Laurence Virgil, Fenske, Kurt James
• Primary Examiner(s): Hofsass, Jeffery
• Assistant Examiner(s): Previl, Daniel
• Application Number:
  US10/280,328
• Time in Patent Office: 760 Days
• Field of Search: 340/664, 340/663, 340/662, 340/660, 340/659, 340/652, 340/649, 340/646, 340/638, 340/657, 340/635, 340/647, 340/650, 340/651, 340/653, 340/691.1, 340/815.4, 324/503, 324/509, 324/512, 324/522, 324/525
• US Class Current: 340/664
• CPC Class Codes: G01R 19/16571 comparing AC or DC current with one threshold, e.g. load current, over-current, surge current or fault current G01R19/16514, G01R19/16519, G01R19/16528, G01R19/16533, G01R19/1659 take precedence; measuring currents by using elements sensitive to the magnetic field generated G01R15/14; measuring earth resistance G01R27/18; testing for leakage or short circuits in electrical apparatus G01R31/52
• CPC Class Codes: G01R 19/2513 Arrangements for monitoring electric power systems, e.g. power lines or loads; Logging

Abstract

A fault indicator for monitoring an electrical conductor has a housing, an indicator flag or a light emitting diode (LED) that becomes visible from the exterior of the fault indicator upon the occurrence of a fault, and electronic circuitry for sensing a fault, for actuating the indicator flag or LED to a fault indicating condition and for resetting the indicator flag or LED to a non-fault indicating condition a predetermined time after the fault has occurred. An overload indicator provides an overload indication, such as a fast flash rate, for a predetermined time when an overload threshold is exceeded, and provides a different overload indication, such as a slow flash rate, for a predetermined time when the line current in the monitored conductor falls below the threshold.

Claims

1. A fault indicator for indicating the occurrence of a fault in an electrical conductor and for indicating an overload condition on said electrical conductor, said fault indicator comprising:

a housing;

a fault sensor for sensing the occurrence of a fault on said electrical conductor;

a fault display for indicating that a fault has occurred, said fault display viewable from the exterior of the housing;

a current sensor for sensing the current load in said conductor;

an overload indicator for indicating that the current load on the conductor is above a predetermined overload value but less than the current load that causes the fault sensor to determine that a fault has occurred, said overload indicator viewable from the exterior of the housing, and

a microprocessor in communication with said fault sensor to determine when a fault has occurred on said electrical conductor and to activate the fault display to a fault displaying condition, in communication with said current sensor to determine if the current load in the electrical conductor is above the predetermined overload value, to activate the overload indicator to an overload displaying condition if the current load is above the predetermined overload value, and to cease activating said overload indicator at a predetermined time after determining that the current load is below the predetermined overload value.

2. The fault indicator as defined in claim 1 wherein said overload indicator is activated when the current load in the electrical conductor remains above the predetermined overload value for a predetermined amount of time.

3. The fault indicator as defined in claim 1 wherein said overload indicator comprises a light emitting diode.

4. The fault indicator as defined in claim 3 wherein said microprocessor activates said light emitting diode at a first on/off rate during the overload condition and said microprocessor continues to activate said light emitting diode at a second on/off rate for a predetermined amount of time after said overload condition ends.

5. The fault indicator as defined in claim 4 wherein said first on/off rate of activating said light emitting diode is faster than said second on/off rate of activating said light emitting diode.

6. The fault indicator as defined in claim 1 wherein said microprocessor terminates activation of the overload indicator if the microprocessor determines that a fault has occurred on the electrical conductor.

7. The fault indicator as defined in claim 1 further comprising a current transformer, said current transformer electromagnetically coupled to said electrical conductor, and said current transformer supplying operating power for said fault indicator, including said microprocessor, said fault display and said light emitting diode.

8. The fault indicator as defined in claim 1 further comprising voltage in-rush restraint circuitry to inhibit said microprocessor from determining that a fault has occurred on said electrical conductor during voltage surges on the electrical conductor.

9. The fault indicator as defined in claim 1 further comprising current in-rush restraint circuitry to inhibit said microprocessor from determining that a fault has occurred on said electrical conductor during current in-rush conditions on the electrical conductor.

10. A fault indicator for indicating the occurrence of a fault in an electrical conductor and for indicating an overload condition on said electrical conductor, said fault indicator comprising:

a housing;

a fault sensor for sensing the occurrence of a fault on said electrical conductor;

a fault display for indicating that a fault has occurred, said fault display viewable from the exterior of the housing;

a current sensor for sensing the current load in said conductor;

an overload indicator for indicating that the current load on the conductor is above a predetermined overload value but less than the current load that causes the fault sensor to determine that a fault has occurred, said overload indicator viewable from the exterior of the housing, and

means for communicating with said fault sensor to determine when a fault has occurred on said electrical conductor and to activate the fault display to a fault displaying condition, means for communicating with said current sensor to determine if the current load in the electrical conductor is above the predetermined overload value, to activate the overload indicator to an overload displaying condition if the current load is above the predetermined overload value, and to cease activating said overload indicator at a predetermined time after determining that the current load is below the predetermined overload value.

11. The fault indicator as defined in claim 10 wherein said overload indicator is activated when the current load in the electrical conductor remains above the predetermined overload value for a predetermined amount of time.

12. The fault indicator as defined in claim 10 wherein said overload indicator comprises a light emitting diode.

13. The fault indicator as defined in claim 10 wherein said light emitting diode is activated at a first on/off rate during the overload condition and said light emitting diode is activated at a second on/off rate for a predetermined amount of time after said overload condition ends.

14. The fault indicator as defined in claim 13 wherein said first on/off rate of activating said light emitting diode is faster than said second on/off rate of activating said light emitting diode.

15. The fault indicator as defined in claim 10 wherein activation of the overload indicator is terminated if said means for communicating with the current sensor determines that a fault has occurred on the electrical conductor.

16. The fault indicator as defined in claim 10 further comprising a current transformer, said current transformer electromagnetically coupled to said electrical conductor, and said current transformer supplying operating power for said fault indicator, including said microprocessor, said fault display and said light emitting diode.

17. The fault indicator as defined in claim 10 further comprising voltage in-rush restraint circuitry to inhibit said means for communicating with the fault sensor from determining that a fault has occurred on said electrical conductor during voltage surges on the electrical conductor.

18. The fault indicator as defined in claim 10 further comprising current in-rush restraint circuitry to inhibit said means for communicating with the fault sensor from determining that a fault has occurred on said electrical conductor during current in-rush conditions on the electrical conductor.