Fault indicator with automatically configured trip settings

• US 6,894,478 B1
• Filed: 06/04/2003
• Issued: 05/17/2005
• Est. Priority Date: 10/26/2001
• Status: Active Grant

• Current Assignee: Schweitzer Engineering Laboratories, Incorporated
• Original Assignee: E.O. Schweitzer Manufacturing Compay, LLC
• Inventors: Fenske, Kurt J.
• Primary Examiner(s): Nguyen, Vinh P.
• Application Number:
  US10/454,851
• Time in Patent Office: 713 Days
• Field of Search: 324/126, 324/127, 324/158.1, 324/117.R, 340/664, 361/63, 361/81
• US Class Current: 324/127
• CPC Class Codes: G01R 15/18 using inductive devices, e.g. transformers
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults
• CPC Class Codes: G01R 31/58 Testing of lines, cables or conductors testing of electric windings G01R31/72
• CPC Class Codes: H02H 3/006 Calibration or setting of parameters

Abstract

A fault indicator for indicating the occurrence of a fault in an electrical conductor has a housing, a high capacity battery, a display for indicating the occurrence of a fault, a current sensor for sensing the load current in a monitored conductor a microcontroller for determining the load current, for selecting one of a plurality of trip settings, such as in several steps between 50 A and 1200 A, based upon the determined load current and for determining that a fault condition occurred when the load current exceeds the trip setting. The selected trip setting is stored in memory. The load current is periodically sampled and the trip setting is changed if the load current falls in a different range. The display may include permanent and temporary fault indicating LEDs and additional internal LEDs that cause the housing to glow or flash at nighttime, or a target style display may be used. Upon the load current exceeding the trip setting, the microcontroller begins flashing the permanent fault LEDs. After a predetermined interval, the microcontroller again senses the load current. If the current is zero, the fault is permanent and the permanent LEDs continue to flash until a timed reset occurs. If load current is present, the fault is temporary and the temporary LED is flashed. If the load current remains above the trip setting, the load had increased and the microcontroller sets a new trip setting. Related methods are also disclosed.

Claims

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

a housing;

a display for indicating that a fault condition has occurred;

said display disposed on the housing such that the display is perceptible by a human;

a current sensor for sensing the load current in said conductor, and for providing a load current signal that is related to the load current;

a microcontroller that is in communication with said load current signal from said current sensor to determine the load current in said conductor;

to select one of a plurality of trip settings based upon the sensed load current in said conductor, to determine that a fault condition has occurred when the load current exceeds the selected trip setting and to actuate the display to the fault indicating condition upon the load current exceeding the selected trip setting.

2. The fault indicator as claimed in accordance with claim 1, said fault indicator further comprising:

a memory that may be accessed by said microcontroller, whereby said microcontroller may store the selected trip setting in said memory.

3. The fault indicator as claimed in accordance with claim 2 wherein said microcontroller will initially reset the trip setting to that previously determined and stored in memory if said conductor is deenergized and the load current is later restored.

4. The fault indicator as claimed in accordance with claim 1 wherein a range of load currents is associated with each of said plurality of trip settings.

5. The fault indicator as claimed in accordance with claim 4 wherein said microcontroller periodically redetermines the load current in said conductor, compares the redetermined load current with the range of load currents associated with each trip setting, and changes the selected trip setting if the redetermined load current falls in a different range of load currents than previously determined.

6. The fault indicator as claimed in accordance with claim 1 wherein said trip settings are selected in the range of about 50 amperes to about 1200 amperes.

7. The fault indicator as claimed in accordance with claim 6 wherein said trip settings are selected from the group consisting of 25, 50, 100, 200, 400, 600, 800, 1000, 1200 and 2500 amperes.

8. The fault indicator as claimed in accordance with claim 1 wherein said microcontroller causes said display to display a fault condition for a predetermined time interval when the load current exceeds the trip setting.

9. The fault indicator as claimed in accordance with claim 8 wherein the predetermined time interval is about one minute.

10. The fault indicator as claimed in accordance with claim 8 wherein said microcontroller reevaluates the load in the conductor at the predetermined time interval.

11. The fault indicator as claimed in accordance with claim 10 wherein said microcontroller determines that the fault condition is permanent if the load current is zero at the predetermined time interval.

12. The fault indicator as claimed in accordance with claim 10 wherein said microcontroller determines that the fault condition is temporary if the load current at the predetermined time interval approximates the load current before the fault condition.

13. The fault indicator as claimed in accordance with claim 10 wherein said microcontroller determines that the fault condition is a change in load current if the load current at the predetermined time interval remains above the trip setting.

14. The fault indicator as claimed in accordance with claim 13 wherein said microcontroller reconfigures the trip setting of the fault indicator to accommodate the higher load current.

15. The fault indicator as claimed in accordance with claim 14 wherein said reconfigured trip setting for the fault indicator is set in accordance with a pre-established range of load current for each trip setting.

16. The fault indicator as claimed in accordance with claim 1 wherein said microcontroller reevaluates the load current at periodic intervals.

17. The fault indicator as claimed in accordance with claim 16 wherein said microcontroller reconfigures the trip setting of the fault indicator if the reevaluated load current falls within a different range than the load current at the last configuration.

18. A method of automatically configuring a fault indicator that detects faults in a monitored electrical conductor, wherein said fault indicator includes a display for displaying a fault condition, a current sensor and a microcontroller, said method comprising the steps of:

sensing the load current in said conductor with the current sensor;

providing a load current signal from the current sensor that is related to the load current in the conductor;

providing a plurality of selectable trip settings for said fault indicator with each trip setting corresponding to a different range of load current;

determining the load current in said conductor based upon the load current signal from the sensor; and

selecting one of the plurality of trip settings based upon the determined load current.

19. The method of automatically configuring a fault indicator in accordance with claim 18, further comprising the additional step of:

determining that a fault condition has occurred when the load current exceeds the selected trip setting.

20. The method of automatically configuring a fault indicator in accordance with claim 19, further comprising the additional steps of:

redetermining the load current in said conductor after a predetermined interval;

determining that a permanent fault has occurred if the load current in the conductor has dropped to near zero.

21. The method of automatically configuring a fault indicator in accordance with claim 20, further comprising the additional step of:

storing information about the status of the permanent fault in memory.

22. The method of automatically configuring a fault indicator in accordance with claim 19, further comprising the additional steps of:

redetermining the load current in said conductor after a predetermined interval; and

determining that a temporary fault has occurred if the load current in the conductor remains above a minimum current value.

23. The method of automatically configuring a fault indicator in accordance with claim 22, further comprising the additional step of:

storing information about the status of the temporary fault in memory.

24. The method of automatically configuring a fault indicator in accordance with claim 19, further comprising the additional step of:

selecting the trip setting from the group consisting of 25, 50, 100, 200, 400, 600, 800, 1000, 1200 and 2500 amperes.

25. The method of automatically configuring a fault indicator in accordance with claim 19, further comprising the additional steps of:

redetermining the load current in said conductor after a predetermined interval;

determining that the load current has increased to a different range of load current if the load current remains above the trip setting after the predetermined interval; and

selecting a new trip setting that is related to the current load current.

26. The method of automatically configuring a fault indicator in accordance with claim 19, further comprising the additional step of:

storing information about the status of the display in memory.

27. The method of automatically configuring a fault indicator in accordance with claim 19, the display of said fault indicator further comprising a temporary fault display and a permanent fault display, further comprising the additional steps of:

storing information about the status of the permanent fault display and the status of the temporary fault display in memory.

28. The method of automatically configuring a fault indicator in accordance with claim 19, said fault indicator further comprising a timed reset of the display at a predetermined time after determining that a fault condition exists, further comprising the additional step of:

storing information about the status of the timed reset in memory.

29. The method of automatically configuring a fault indicator in accordance with claim 18, further comprising the additional step of:

storing the selected trip setting in memory.

30. The method of automatically configuring a fault indicator in accordance with claim 18, further comprising the additional steps of:

periodically redetermining the load current in said conductor; and

changing the trip setting of the fault indicator if the redetermined load current falls in a different range of load currents than the previously determined load current.