MEANS FOR DETECTING FAULT CURRENT IN A CONDUCTOR AND INDICATING SAME AT A REMOTE POINT

• US 3,866,197 A
• Filed: 12/10/1973
• Issued: 02/11/1975
• Est. Priority Date: 12/10/1973
• 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): Caldwell, John W.
• Assistant Examiner(s): Myer, Daniel
• Application Number:
  US05/423,283
• Time in Patent Office: 428 Days
• Field of Search: 340/248,253,255,214 324/51,133 317/22,33SD,58 335/205,206,207
• US Class Current: 340/651
• CPC Class Codes: G01R 19/15 Indicating the presence of current

Abstract

The rectified output of one or more current transformers associated respectively with one or more conductors of a high voltage alternating current system is applied to a fault responsive winding on a magnetic circuit of a fault responsive device for magnetizing it with unidirectional magnetic flux in one direction. A normally open reed switch in the magnetic field of the magnetic circuit is closed on flow of fault current in one or more of the conductors and is connected to control signalling or control means located at a point remote from the fault responsive device. For demagnetizing the magnetic circuit, a reset winding is positioned on the magnetic circuit and is connected for energization to a direct current source under the control of a manually operable switch at the remote point.

Claims

1. Means for detecting flow of fault current in a high voltage alternating current carrying conductor and indicating the same at a remote point comprising:

a fault responsive device including a magnetic circuit, a fault responsive winding on said magnetic circuit, means for energizing said fault responsive winding with direct current according to the magnitude of flow of alternating fault current in said conductor, a reset winding on said magnetic circuit, and a normally open reed switch adjacent said magnetic circuit arranged to be closed on energization of said fault responsive winding resulting from flow of fault current in said conductor;

indicating means at a said remote point connected to be responsive to closure of said reed switch, and means at said remote point for connecting said reset winding to a direct current source for reversing the magnetization of said magnetic circuit and opening said reed switch.

2. Fault current flow detecting and indicating means according to claim 1 wherein said direct current source is located at said remote point, and manually operable switch means at said remote point is arranged to connect said direct current source to said reset winding.

3. Fault current flow detecting and indicating means according to claim 1 wherein said indicating means includes a relay having an operating winding that is energized when said reed switch is closed, and contacts operated by said operatIng winding.

4. Fault current flow detecting and indicating means according to claim 1 wherein signalling means are located adjacent said fault responsive means and at said remote point to indicate that fault current has flowed in said conductor.

5. Fault current flow detecting and indicating means according to claim 1 wherein rectifier means individual to each of said windings are connected across the same to prevent energization of said fault responsive winding on energization of said reset winding.

6. Fault current flow detecting and indicating means according to claim 4 wherein said signalling means includes a light emitting diode that is illuminated on closure of said reed switch.

7. Fault current flow detecting and indicating means according to claim 6 wherein one light emitting diode is located adjacent said fault responsive device and another light emitting diode is located at said remote point.

8. Fault current flow detecting and indicating means according to claim 6 wherein said light emitting diode is located at said remote point and is connected in series with said reset winding and said reed switch.

9. Fault current flow detecting and indicating means according to claim 8 wherein a rectifier shunts said light emitting diode and is oppositely poled to permit flow of reset current to said reset winding.

10. Fault current flow detecting and indicating means according to claim 7 wherein said light emitting diodes are connected in series with each other and with said reed switch.

11. Fault current flow detecting and indicating means according to claim 2 wherein said manually operable switch means comprises a double pole double throw switch arranged in one position to test the condition of said reed switch and in another position to energize said reset winding.

12. Fault current flow detecting and indicating means according to claim 1 wherein a pivoted permanent magnet is located adjacent said magnetic circuit and is arranged to be shifted from a normal position to an operated position on flow of predetermined fault current in said conductor, one end of said reed switch is located adjacent said pivoted permanent magnet to close said reed switch when said pivoted permanent magnet is shifted to said operated position, and a biasing permanent magnet is located adjacent the other end of said reed switch to hold said reed switch in closed position until the magnetization of said magnetic circuit is reversed on energization of said reset winding.

13. Fault current flow detecting and indicating means according to claim 12 wherein said reset winding is connected in series with said reed switch.