Two part clamping and suspension mechanism for a split toroidal current transformer

Patent metadata

Field	Value
Publication number	US-10971295-B2
Application number	US-201816207593-A
Country	US
Kind code	B2
Filing date	Dec 3, 2018
Priority date	Dec 3, 2018
Publication date	Apr 6, 2021
Grant date	Apr 6, 2021

Abstract

The present disclosure relates to ensuring contact between core halves of a current transformer. For example, a current transformer (CT) may include a split core comprising a first core half having a first plurality of faces and a second core half having a second plurality of faces. Each face of the first core half may contact a corresponding face of the second core half to allow magnetic flux to flow through the split core to induce current on windings of the CT. The CT may include a first housing that houses the first core half and a second housing that the second core half. The CT may include a biasing element that biases the second core half towards the first core half to ensure that each face of the second core half contacts the corresponding face of the first core half.

First claim

What is claimed is:

1. A current transformer (CT), comprising:
a split core comprising a first core half having a first plurality of faces and a second core half having a second plurality of faces, wherein each face of the first core half is configured to contact a corresponding face of the second core half to allow magnetic flux to flow through the split core to induce current on windings of the CT;
a first housing configured to house the first core half;
a second housing rotatably coupled to the first housing and configured to house the second core half, wherein the first housing and the second housing, when rotated to an open position, form an opening to allow a conductor to be inserted between the first core half and the second core half, and when rotated to a closed position, close the opening between the first core half and the second core half to form an annulus around the conductor;
a biasing element configured to bias the second core half towards the first core half to ensure that each face of the second core half contacts the corresponding face of the first core half, wherein the biasing element is configured to position each face of the first plurality of faces to be parallel to the corresponding face of the second plurality of faces to account for differences in surfaces between the first plurality of faces and the second plurality of faces
a first overmold configured to secure windings of the CT to the first core half; and
a second overmold configured to secure windings of the CT to the second core half, wherein the second overmold comprises a protrusion to support the second overmold on the biasing element and a boss configured to engage an axial opening of the biasing element to stabilize the overmold on the biasing element.

2. The CT of claim 1 , wherein the second housing comprises an annular body configured to receive the biasing element within the annular body to maintain the lateral position of the biasing element with respect to the second housing while enabling the biasing element to compress and expand axially with respect to the annular body.

3. The CT of claim 1 , wherein the biasing element comprises a compression spring positioned in the second housing, wherein the compression spring is configured to apply an expanding force from the second housing to the second core half in a direction towards the first core half to ensure that each face of the second core half contacts the corresponding face of the first core half.

4. The CT of claim 3 , wherein the compression spring is configured to be at least partially compressed when the CT is in the closed position to maintain contact between the second core half and the first core half.

5. The CT of claim 1 , wherein the first housing comprises a first saddle configured to secure a first overmold of the first core half within the first housing.

6. The CT of claim 5 , wherein the first saddle comprises openings configured to receive corresponding faces of the first core half to allow each face of the first core half to contact the corresponding face of the second core half.

7. The CT of claim 1 , wherein the second housing comprises a second saddle configured to secure a second overmold of the second core half within the second housing.

8. The CT of claim 7 , wherein the second saddle comprises openings configured to receive corresponding faces of the second core half to allow each face of the second core half to contact the corresponding face of the first core half.

9. A faulted circuit indicator (FCI), comprising:
a current transformer (CT), comprising:
an annular split core having a first core half with a first plurality of faces and a second core half with a second plurality of faces, wherein each face of the first core half is configured to contact a corresponding face of the second core half to allow magnetic flux to flow through the annular split core to induce current on windings of the CT;
a first housing configured to house the first core half;
a second housing rotationally coupled to the first housing, wherein the second housing is configured to house the second core half;
wherein the first housing and the second housing, when rotated to an open position, form an opening to allow a conductor of an electric power system to be inserted between the first core half and the second core half, and when rotated to a closed position, close the opening between the first core half and the second core half to form an annulus around the conductor; and
a biasing element configured to bias the second core half towards the first core half to ensure that each face of the second core half contacts the corresponding face of the first core half, wherein the biasing element is configured to position each face of the first core half to be parallel to the corresponding face of the second core half to account for differences in surfaces between the first core half and the second core half;
a first overmold configured to secure windings of the CT to the first core half; and
a second overmold configured to secure windings of the CT to the second core half, wherein the second overmold comprises a protrusion to support the second overmold on the biasing element and a boss configured to engage an axial opening of the biasing element to stabilize the overmold on the biasing element;

detection circuitry configured to:
receive a signal from the current transformer indicating current on the conductor; and
detect an event on the electric power system based on the current on the conductor.

10. The FCI of claim 9 , wherein the biasing element comprises a compression spring.

11. The FCI of claim 9 , wherein the biasing element is configured to flexibly exert a force on the second core half towards a contact position with the first core half such that the biasing element causes sufficient contact between the first core half and the second core half to induce current on the windings.

12. The FCI of claim 9 , wherein the second housing comprises a midplane that separates the CT from the detection circuitry, wherein the biasing element is positioned orthogonal to the midplane.

13. The FCI of claim 9 , wherein the first housing comprises a first saddle configured to secure a first overmold of the first core half within the first housing.

14. The FCI of claim 13 , wherein the first saddle comprises openings configured to receive corresponding faces of the first core half to allow each face of the first core half to contact the corresponding face of the second core half.

15. The FCI of claim 9 , wherein the second housing comprises a second saddle configured to secure a second overmold of the second core half within the second housing.

16. The FCI of claim 15 , wherein the second saddle comprises openings configured to receive the faces of the second core half to contact the faces of the first core half.

17. A method, comprising:
covering a first core half of a current transformer (CT) with a first overmold;
covering a second core half of the CT with a second overmold;
inserting the first overmold into a first housing of the CT;
inserting the second overmold into a second housing;
inserting at least one biasing element into the second housing;
movably coupling the second overmold to the at least one biasing element to bias the second core half towards the first core half to ensure that faces of the second core half contact corresponding faces of the first core half, wherein the second overmold comprises a protrusion to support the second overmold on the biasing element and a boss configured to engage an axial opening of the

Assignees

• Schweitzer Engineering Lab Inc

Inventors

• Thomas Mark A
• Ryan Eric

Classifications

• H01F27/28

  Coils; Windings; Conductive connections · CPC title

• H01F30/16

  Toroidal transformers · CPC title

• G01R15/186

  using current transformers with a core consisting of two or more parts, e.g. clamp-on type (G01R15/142 - G01R15/16 take precedence; tong testers G01R1/22) · CPC title

• H01F38/20

  Instruments transformers · CPC title

• H01F27/02

  Casings · CPC title