Fault indicator and means for resetting the same

• US 4,086,529 A
• Filed: 07/26/1976
• Issued: 04/25/1978
• Est. Priority Date: 07/26/1976
• Status: Expired due to Term

• Current Assignee: Edmund O. Schweitzer Jr
• Original Assignee: Edmund O. Schweitzer Jr
• Inventors: Schweitzer, Edmund O. Jr.
• Primary Examiner(s): Rolinec, Rudolph V.
• Assistant Examiner(s): Karlsen, Ernest F.
• Application Number:
  US05/708,549
• Time in Patent Office: 638 Days
• Field of Search: 324/127, 324/133, 324/102, 324/51, 340/253 A, 340/253 P
• US Class Current: 324/127
• CPC Class Codes: G01R 19/15 Indicating the presence of current

Abstract

A fault indicator for alternating current distribution systems includes a pair of spaced pole pieces for receiving therebetween at one end the conductor and at the other end a pivoted permanent magnet carrying a target that is biased to a fault indicating position by a stationary permanent magnet. The pole pieces are demagnetized on flow of fault current in the conductor. They are remagnetized by a winding which is energized by discharge of a capacitor that is charged through a rectifier from an oscillator circuit. The winding is carried by a receptacle into which the other ends of the pole pieces are inserted and a circuit is completed thereby to charge the capacitor. The receptacle is carried at one end of a tubular housing the other end of which has an eye to receive a claw of a live line tool for applying the fault indicator to and removing it from the conductor.

Claims

1. A fault indicator responsive to the occurrence of an alternating fault current of predetermined minimum amplitude in a conductor and means for resetting the same, comprising in combination:

a generally cylindrical housing;

a target mounted at one end of said housing for rotation in a plane generally perpendicular to the axis of said housing between a fault indicating position and a reset position, at least a portion of said target being visible from the exterior of said housing to indicate the position of said target;

a target permanent magnet having diametrically opposed magnetic poles of like gender mounted for rotation with said target;

a stationary permanent magnet of high coercive force disposed in magnetic communication with said target magnet, and having magnetic poles arranged for biasing said target magnet to position said target in said fault indicating position;

a pair of pole pieces extending longitudinally in generally parallel-spaced relationship within said housing from said one end of said housing to the other end thereof, each of said pole pieces being formed of a magnetizable material of low coercive force subject to being demagnetized upon occurrence of a current in the conductor in excess of said predetermined minimum level, said pole piece each including an end portion projecting from said other end of said housing and defining therewith means for receiving the conductor, the other ends of said pole pieces being disposed in magnetic communication with opposing poles of said target magnet;

and reset means comprising a receptacle dimensioned for telescopic engagement with said housing and including winding coaxially disposed therein for magnetic communication with said pole pieces when said housing is seated in said receptacle for magnetizing said pole pieces whereby said other ends thereof bias said target magnet to position said target in said reset position.

3. The fault indicator and resetting means called for in claim 1 wherein said permanent magnets are each circular magnets having four equally spaced poles with poles of like gender being diametrically located.

4. The fault indicator and resetting means called for in claim 1 wherein spring means are provided on said housing for detachably securing said conductor between said projecting portions of said pole pieces.

5. The fault indicator and resetting means called for in claim 1 wherein conducting means overlie at least one of said pole pieces for limiting the reduction in magnetic flux therein resulting from transient current flow in said conductor.

6. The fault indicator and resetting means called for in claim 1 wherein said other ends of said pole pieces are magnetized to the same polarity.

7. The fault indicator and resetting means called for in claim 1 wherein said means for magnetizing said pole pieces include means for energizing said winding from a source of direct current.

8. The fault indicator and resetting means called for in claim 7 wherein said means for energizing said winding are responsive to said housing being received within said receptacle.

9. The fault indicator and resetting means called for in claim 3 wherein said means for energizing said winding include a capacitor, and means for charging said capacitor.

14. A fault indicator as defined in claim 1 wherein said target is mounted for rotation about the axis of said housing.

15. A fault indicator as defined in claim 1 wherein said end portions of said pole pieces are radially outwardly flared.

2. A fault indicator responsive to the occurrence of an alternating fault current of predetermined minimum amplitude in a conductor comprising, in combination:

a generally cylindrical housing;

a target mounted at one end of said housing for rotation in a plane generally perpendicular to the axis of said housing between a fault indicating position and reset position, at least a portion of said target being visible from the exterior of said housing to indicate the position of said target;

a target permanent magnet having diametrically opposed magnetic poles of like gender mounted for rotation with said target;

a stationary permanent magnet of high coercive force disposed in magnetic communication with said target magnet, and having magnetic poles arranged for biasing said target magnet to position said target in said fault indicating position; and

a pair of pole pieces extending longitudinally in generally parallel-spaced relationship within said housing from one end of said housing to other end thereof, each of said pole pieces being formed of a magnetizable material of low coercive force subject to being demagnetized upon occurrence of a current in the conductor in excess of said predetermined minimum level, said pole pieces each including an end portion projecting from said other end of said housing and defining therewith means for receiving the conductor, the other ends of said pole pieces being disposed in magnetic communication with opposing poles of said target magnet so as to bias said target magnet to position said target in said reset position.

10. The fault indicator called for in claim 2 wherein said permanent magnets are each permanent magnets having four equally spaced poles with of like gender being diametrically located.

11. The fault indicator called for in claim 2 wherein spring means are provided on said housing for detachably securing said conductor between said projecting portions of said pole pieces.

12. The fault indicator called for in claim 2 wherein conducting means overlie at least one of said pole pieces for limiting the reduction in magnetic flux therein resulting from transient current flow in said conductor.

13. The fault indicator called for in claim 2 wherein said other ends of said pole pieces are magnetized to the same polarity.

16. A fault indicator as defined in claim 2 wherein said target is mounted for rotation about the axis of said housing.

17. A fault indicator as defined in claim 2 wherein said end portions of said pole pieces are radially outwardly flared.