Fault indicator having auxiliary fault sensing winding

• US 5,677,678 A
• Filed: 04/08/1996
• Issued: 10/14/1997
• Est. Priority Date: 04/08/1996
• Status: Expired due to Fees

• Current Assignee: Edmund O. Schweitzer III, Jean E. Schweitzer, Marilyn L. Schweitzer
• Original Assignee: Edmund O. Schweitzer Jr
• Inventors: Schweitzer, Edmund O. Jr.
• Primary Examiner(s): Mullen, Thomas
• Assistant Examiner(s): TWEEL JR, JOHN ALEXANDER
• Application Number:
  US08/628,087
• Time in Patent Office: 554 Days
• Field of Search: 340/664, 340/650, 324/96, 324/133, 324/508
• US Class Current: 340/664
• CPC Class Codes: G01R 15/188 comprising rotatable parts, e.g. moving coils galvanometers G01R5/02, G01R5/14

Abstract

A fault indicator is described which indicates the occurrence of a fault current in a monitored electrical conductor. The fault indicator includes a magnetic pole assembly which mounts the housing of the fault indicator to the monitored electrical conductor. The magnetic pole assembly includes both a main outer magnetic core assembly and an auxiliary inner magnetic core assembly. As described, an auxiliary fault sensing winding is disposed on the inner magnetic core assembly so that it becomes energized and provides power for fault circuitry within the fault indicator upon the occurrence of a fault current in the monitored electrical conductor. The fault circuitry positions a flag indicator within the module to visibly acknowledge the occurrence of the fault current in the electrical conductor. As disclosed, two air gaps prevent the inner magnetic core assembly from communicating magnetic flux from the main core assembly to the auxiliary fault sensing winding while a current sufficiently less than a fault current flows within the monitored electrical conductor.

Claims

1. A fault indicator for indicating an occurrence of a fault current in an electrical conductor of a monitored cable comprising:

a housing;

status indicating means within said housing, said status indicating means having a reset indicating state and a fault indicating state;

a magnetic pole assembly mounting said housing to said monitored cable;

a first magnetic core within said magnetic pole assembly, said first magnetic core being responsive to a current in said electrical conductor;

a second magnetic core within said magnetic pole assembly, said second magnetic core being responsive to said occurrence of said fault current in said electrical conductor;

reset circuit means for conditioning said status indicating means to said reset indicating state, said reset circuit means including a reset power winding wound on said first magnetic core, said reset power winding being energized by said current in said electrical conductor; and

trip circuit means for conditioning said status indicating means to said fault indicating state in response to said occurrence of said fault current in said electrical conductor, said trip circuit means including an auxiliary fault sensing winding independent of said reset power winding and wound on said second magnetic core, said auxiliary fault sensing winding and said second magnetic core being disposed within a perimeter of said first magnetic core, said auxiliary fault sensing winding being energized by said fault current in said electrical conductor.

2. A fault indicator as defined in claim 1, wherein said second magnetic core includes second isolating means for magnetically isolating said second magnetic core from a normal current flow in said electrical conductor.

3. A fault indicator as defined in claim 2, wherein said second isolating means comprises at least one air gap.

4. A fault indicator as defined in claim 3, wherein said second isolating means comprises an additional air gap.

5. A fault indicator as defined in claim 4, wherein said at least one air gap is intermediate a first end of said second magnetic core and an inside surface of said first magnetic core.

6. A fault indicator as defined in claim 5, wherein said additional air gap is intermediate of a second end of said second magnetic core and an inside surface of said first magnetic core.

7. A fault indicator as defined in claim 3, wherein said at least one air gap is of a predetermined size.

8. A fault indicator as defined in claim 4, wherein said additional air gap is of a predetermined size.

9. A fault indicator for indicating an occurrence of a fault current in an electrical conductor of a monitored cable comprising:

a housing;

status indicating means within said housing, said status indicating means having a reset indicating state and a fault indicating state;

a magnetic pole assembly connecting said housing to said monitored cable;

a first magnetic core within said magnetic pole assembly, said first magnetic core being responsive to a current in said electrical conductor;

a second magnetic core within said magnetic pole assembly, said second magnetic core being responsive to said occurrence of said fault current in said electrical conductor;

a first end of said second magnetic core being adjacent to an inside surface of said first magnetic core and forming a first air gap intermediate said first end and said inside surface of said first magnetic core;

a second end of said second magnetic core being adjacent to said inside surface of said first magnetic core and forming an additional air gap intermediate said first end;

reset circuit means for conditioning said status indicating means to said reset indicating state, said reset circuit means including a reset power winding, said reset power winding being wound on said reset power winding, said reset power winding further being energized by said current in said electrical conductor; and

trip circuit means for conditioning said status indicating means to said fault indicating state in response to said occurrence of said fault current in said electrical conductor, said trip circuit means including an auxiliary fault sensing winding independent of said reset power winding, said auxiliary fault sensing winding being disposed within a perimeter of said first magnetic core, said auxiliary fault sensing winding being further wound on said second magnetic core, said auxiliary fault sensing winding further being energized by said fault current in said electrical conductor.