Shielded Rogowski coil assembly and methods

• US 20080106253A1
• Filed: 11/06/2006
• Published: 05/08/2008
• Est. Priority Date: 11/06/2006
• Status: Active Grant

• Current Assignee: Eaton Intelligent Power Limited (Eaton Corporation PLC.)
• Original Assignee: Cooper Technologies Company (Eaton Corporation PLC.)
• Inventors: Kojovic, Ljubomir A.
• Granted Patent: US 7,564,233 B2
• Time in Patent Office: Days
• US Class Current: 324/127
• CPC Class Codes: G01R 15/181 using coils without a magnetic core, e.g. Rogowski coils
• CPC Class Codes: G01R 15/247 Details of the circuitry or construction of devices covered by G01R15/241 - G01R15/246
• CPC Class Codes: H01F 27/36 Electric or magnetic shields or screens movable for varying inductance H01F21/10
• CPC Class Codes: H01F 27/366 made of ferromagnetic material
• CPC Class Codes: H01F 38/30 Constructions
• CPC Class Codes: H01F 5/003 Printed circuit coils

Abstract

Shielded Rogowski coil systems having separate interface cables and methods for eliminating and monitoring noise in signal transmissions over the cables.

Claims

1. A Rogowski coil assembly comprising:

a first Rogowski coil surrounding a conductor and generating a first voltage output signal; and

a second Rogowski coil surrounding the conductor and generating a second voltage output signal;

wherein the first voltage output signal and the second voltage output signal are processed to address noise components in the first and second output voltage signal.

2. The Rogowski coil assembly of claim 1, wherein each of the first coil portion and the second coil portion are fabricated on printed circuit boards.

3. The Rogowski coil assembly of claim 1, wherein the first and second coils are electrically connected in opposite directions.

4. The Rogowski coil assembly of claim 1, further comprising first and second interface conductors for the respective first and second coils, the first and second conductors being terminated to the respective coils at one end thereof, and the terminations being magnetically shielded to prevent voltages from being induced in the interface conductors at the terminations.

5. The Rogowski coil assembly of claim 1, further comprising first and second interface conductors for the respective first and second coils, the first and second interface conductors being surrounded by a common magnetic shield.

6. The Rogowski coil assembly of claim 1, further comprising first and second interface conductors for the respective first and second coils, at least one of the conductors being a coaxial cable.

7. The Rogowski coil assembly of claim 1, further comprising first and second interface conductors for the respective first and second coils, at least one of the conductors being a twisted pair wire.

8. The Rogowski coil assembly of claim 1, further comprising first and second interface conductors for the respective first and second coils, the interface conductors being connected in series.

9. The Rogowski coil assembly of claim 1, further comprising first and second interface conductors for the respective first and second coils, the first and second interface conductors being connected to a protective relay device, the relay device programmed to determine a level of noise in the first and second output voltage signal.

10. The Rogowski coil assembly of claim 1, further comprising first and second interface conductors for connecting the first and second coils to a protective relay device, the relay device programmed to cancel noise in the first and second output voltage signal.

11. A Rogowski coil assembly comprising:

a first Rogowski coil comprising a first printed circuit board and a first conductive winding thereon, the first coil surrounding a conductor and generating a first voltage output signal proportional to a rate of change of current flowing through the conductor;

a second Rogowski coil comprising a second printed circuit board and a second conductive winding thereon, the second coil surrounding the conductor and generating a second voltage output signal proportional to the rate of change of current flowing through the conductor; and

a pair of interface conductors, each of the pair of interface conductors transmitting one of the first and second voltage output signals.

12. The Rogowski coil assembly of claim 11, wherein the first and second coils extend in opposite directions.

13. The Rogowski coil assembly of claim 11, wherein each of the first and second conductors are terminated to the respective first and second coils, and the terminated conductors are magnetically shielded to prevent voltages from being induced in the interface conductors at the termination locations.

14. The Rogowski coil assembly of claim 11, wherein the first and second interface conductors are surrounded by a common magnetic shield.

15. The Rogowski coil assembly of claim 11, at least one of the first and second interface conductors being a coaxial cable.

16. The Rogowski coil assembly of claim 11, at least one of the conductors being a twisted pair wire.

17. The Rogowski coil assembly of claim 11, wherein the first and second interface conductors are connected in series.

18. The Rogowski coil assembly of claim 11, further comprising a microprocessor based device connected to each of the first and second interface conductors, the microprocessor based device programmed to determine a level of noise in first and second output voltage signal.

19. The Rogowski coil assembly of claim 11, further comprising a microprocessor based device connected to each of the first and second interface conductors, the microprocessor based device programmed to cancel noise in first and second output voltage signal.

20. A Rogowski coil system comprising:

a conductor;

a first Rogowski coil comprising a conductive circuit board and a right handed coil formed thereon, the right handed coil receiving the conductor generating a first voltage output when the conductor is energized;

a second Rogowski coil comprising a conductive circuit board and a left handed coil formed thereon, the left-handed coil receiving the conductor and generating a generating a second voltage output when an energized conductor is passed through the coil;

a first interface conductor terminated to the first coil; and

a second interface conductor separately provided form the first interface conductor, the second interface conductor terminated to the second coil.

21. The Rogowski coil assembly of claim 20, further comprising magnetic shields protecting an area of termination of the respective interface conductors to each of the first and second coils.

22. The Rogowski coil assembly of claim 20, wherein the first and second interface conductors are surrounded by a common magnetic shield.

23. The Rogowski coil assembly of claim 20, wherein the interface conductors are selected from the group of a coaxial cable, a twisted pair wire, and combinations thereof.

24. The Rogowski coil assembly of claim 20, wherein the first and second interface conductors are connected in series.

25. The Rogowski coil assembly of claim 25, further comprising a microprocessor based device connected to each of the first and second interface conductors, the microprocessor based device programmed to determine a level of noise in first and second output voltage signal.

26. The Rogowski coil assembly of claim 25, further comprising a microprocessor based device connected to each of the first and second interface conductors, the microprocessor based device programmed to cancel noise in first and second output voltage signal.

27. A method of monitoring current with a Rogowski coil assembly, the method comprising:

providing a first Rogowski coil having a first winding;

providing a second Rogowski coil having a first winding extending opposite to the first winding;

connecting an interface conductor to each of the first and second coils;

obtaining distinct voltage outputs from each of the first and second Rogowski coils; and

applying a noise effect algorithm, using a microprocessor based device, to the voltage outputs.

28. The method of claim 27, wherein applying a noise effect algorithm comprises determining an amount of noise in the voltage outputs.

29. The method of claim 28 wherein determining an amount of noise comprises adding the voltage outputs conducted through the first and second interface conductor

30. The method of claim 27, wherein applying a noise effect algorithm comprises minimizing an amount of noise in the voltage outputs.

31. The method of claim 30 wherein minimizing an amount of noise in the voltage outputs comprises subtracting the voltage outputs conducted through the first and second interface conductor

32. A Rogowski coil system comprising:

first and second sensing coils formed on respective circuit boards and configured for induced voltage measurements corresponding to current flow in a conductor passing through the coil; and

means for monitoring noise conditions during operation of the coils.

33. The system of claim 32 further comprising means for shielding the first and second sensing coils.

34. The system of claim 32 further comprising means for interfacing the first and second sensing coils with the means for monitoring.

35. The system of claim 35 further comprising means for shielding the connection of the means for interfacing with the means for monitoring.