CURRENT MEASURING AND AUTOMATICALLY RESETTABLE FAULT INDICATING MEANS

• US 3,702,966 A
• Filed: 03/01/1971
• Issued: 11/14/1972
• Est. Priority Date: 03/01/1971
• 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): Strecker, Gerard R.
• Application Number:
  US05/119,639
• Time in Patent Office: 624 Days
• Field of Search: 324/51,102,133,127 340/253 317/22
• US Class Current: 324/133
• CPC Class Codes: G01R 15/188 comprising rotatable parts, e.g. moving coils galvanometers G01R5/02, G01R5/14
• CPC Class Codes: G01R 19/15 Indicating the presence of current
• 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

Abstract

A capacitor is charged through a capacitive coupling to a high voltage alternating current electric power conductor and is discharged when the charge reaches a predetermined value to reset fault indicator that previously had been operated by flow of fault current in the conductor. The magnetic circuit employs a demagnetizable low coercive force core in the form of a bifurcated yoke or a ring having magnetizing windings energized on discharge of the capacitor. A manually resettable fault indicator employing a demagnetizing winding on a low coercive force ring also is disclosed.

Claims

1. An automatically resettable fault indicator for an alternating current conductor comprising:

a demagnetizable magnetic core adapted to embrace said conductor and normally energized with unidirectional magnetic flux to provide a pair of opposite poles and adapted to be demagnetized in accordance with the magnitude of alternating current flow in said conductor, a stationary permanent magnet having its poles adjacent unlike poles of said magnetic core, a pivotable permanent magnet adjacent said stationary permanent magnet taking up a normal position when the magnetic field from said poles of said magnetic core is greater than the magnetic field from said poles of said permanent magnet, magnetizing winding means on said magnetic core insulated from and adapted to be capacitively coupled to said conductor, a counterpoise spaced from said conductor, switch means, a capacitor connected across said winding means through said switch means, and a pair of series connected rectifiers connected across said capacitor with the common connection therebetween connected to said counterpoise, said pivotable permanent magnet being shifted to an alternate position when the alternating current flow in said conductor exceeds a predetermined value and effects a corresponding reduction in said magnetic field from said poles of said magnetic core, energization of said conductor charging said capacitor, and closure of said switch means discharging said capacitor through said winding means to restore to normal said magnetic field from said poles of said magnetic core and effect movement of said pivotable permanent magnet to said normal position thereof.

2. The fault indicator according to claim 1 wherein said winding means comprises a pair of series connected windings arranged on said magnetic core in opposite winding directions to generate said opposite poles on flow therethrough of direct current.

3. The fault indicator according to claim 1 wherein said counterpoise is charged to one polarity during one half cycle of the flow of alternating current in said conductor and said capacitor is charged with the same polarity during the next half cycle of the fLow of alternating current in said conductor.

4. The fault indicator according to claim 1 wherein means responsive to the application of a predetermined charge on said capacitor effect closure of said switch means to discharge said capacitor as aforesaid.

5. The fault indicator according to claim 1 wherein said switch means includes an SCR, and a space discharge device responsive to the charge on said capacitor renders said SCR conducting when said charge reaches a predetermined value.

6. The fault indicator according to claim 1 wherein said magnetic core is in the form of a ring, said winding means comprises a pair of windings wound in opposite winding directions on said ring, and means connect said windings in series circuit relation.

7. The fault indicator according to claim 6 wherein said magnetic core is arranged to receive therethrough said alternating current carrying conductor.

8. An automatically resettable fault indicator for an alternating current conductor comprising:

a demagnetizable bifurcated yoke of magnetic material for application to said conductor such that the arms thereof are normally energized with unidirectional magnetic flux to have opposite poles at the distal ends of said arms and are subjected to demagnetization in accordance with the magnitude of alternating current flow in said conductor, a stationary permanent magnet between the distal ends of said arms having its poles adjacent unlike poles thereof, a pivotable permanent magnet adjacent said stationary permanent magnet taking up a normal position when the magnetic field from said poles at said distal ends is greater than the magnetic field from said poles of said permanent magnet, a magnetizing winding surrounding each of said arms insulated from and adapted to be capacitively coupled to said conductor, a counterpoise spaced from said conductor, switch means, a capacitor connected across said windings through said switch means, and a pair of series connected rectifiers connected across said capacitor with the common connection therebetween connected to said counterpoise, said pivotable permanent magnet being shifted to an alternate position when the alternating current flow in said conductor exceeds a predetermined value and effects a corresponding reduction in said magnetic field from said poles at said distal ends, energization of said conductor charging said capacitor, and closure of said switch means discharging said capacitor through said windings to restore to normal said magnetic field from said distal ends and effect movement of said pivotable permanent magnet to said normal position thereof.

9. The fault indicator according to claim 8 wherein means connect said magnetizing windings in series circuit relation.

10. The fault indicator according to claim 8 wherein said counterpoise is charged to one polarity during one half cycle of the flow of alternating current in said conductor and said capacitor is charged with the same polarity during the next half cycle of the flow of alternating current in said conductor.

11. The fault indicator according to claim 8 wherein means responsive to the application of a predetermined charge on said capacitor effect closure of said switch means to discharge said capacitor as aforesaid.

12. the fault indicator according to claim 8 wherein said switch means includes an SCR, and a space discharge device responsive to the charge on said capacitor renders said SCR conducting when said charge reaches a predetermined value.