High voltage fault current limiter having immersed phase coils

1. A fault current limiter, comprising:

a ferromagnetic circuit formed from a ferromagnetic material and including at least a first limb, and a second limb;

a saturation mechanism surrounding the first limb for magnetically saturating the ferromagnetic material of the second limb; and

a phase coil surrounding the second limb, wherein:

the phase coil is immersed in a dielectric fluid; and

the saturation mechanism is not immersed in a dielectric fluid.

2. A fault current limiter as claimed in claim 1 , wherein the saturation mechanism comprises a cooled superconducting coil for interconnecting to a DC power supply.

3. A fault current limiter as claimed in claim 2 , wherein the superconducting coil is within a cryostat.

4. A fault current limiter as claimed in claim 1 , further comprising:

an external vessel housing the ferromagnetic circuit, the saturation mechanism, the phase coil, and the dielectric fluid; and

a series of terminals mounted on the external vessel,

wherein the phase coil includes an AC input lead and an AC output lead interconnected to predetermined ones of the terminals.

5. A fault current limiter as claimed in claim 4 , further comprising a low temperature cooling supply hose interconnected to the saturation mechanism.

6. A fault current limiter as claimed in claim 1 , wherein the limiter is utilised in a multiphase power supply to limit each phase of the supply.

7. A fault current limiter as claimed in claim 6 , wherein a single saturation mechanism surrounds the ferromagnetic circuit of each phase of the multiphase power supply.

8. A fault current limiter as claimed in claim 1 , wherein:

the ferromagnetic circuit comprises an elongated portion of ferromagnetic material;

a first segment of the elongated portion forms the first limb; and

a second segment of the elongated portion forms the second limb, such that the saturation mechanism and the phase coil are formed around the same elongated portion of ferroelectric material.

9. A fault current limiter as claimed in claim 8 , wherein the saturation mechanism is formed around the first segment located at a proximal end of the elongated portion and the phase coil is formed around the second segment located at a distal end of the elongated portion.

10. A fault current limiter as claimed in claim 8 , wherein the ferromagnetic circuit comprises a single elongated portion of ferroelectric material.

11. A fault current limiter as claimed in claim 1 , wherein the ferromagnetic circuit includes a first, second and third limbs parallel to one another, with portions of the phase coil wound around the first and second limb, with the saturation mechanism wound around the third limb.

12. A fault current limiter as claimed in claim 1 , wherein the limiter has a normal operating range of substantially 33 kV to 750 kV.

13. A fault current limiter as claimed in claim 1 , wherein the saturation mechanism magnetically saturates the ferromagnetic material of the second limb during non fault conditions.

14. A fault current limiter as claimed in claim 1 , wherein the first and second limbs are adjacent one another and the saturation mechanism and the phase coil are of substantially the same size or extent.

15. A fault current limiter as claimed in claim 1 , wherein the saturation mechanism is surrounded by a gaseous atmosphere.

16. A fault current limiter, comprising:

a ferromagnetic circuit formed from a ferromagnetic material and including at least a first limb, a second limb; a third limb; a fourth limb;

a saturation mechanism surrounding the first limb for magnetically saturating the ferromagnetic material of the second, third and fourth limbs; and

a first phase coil surrounding the second limb; a second phase coil surrounding the third limb and a third phase coil surrounding the fourth limb, wherein:

the phase coils are immersed in a dielectric fluid, and

the saturation mechanism is not immersed in a dielectric fluid.

17. A fault current limiter as claimed in claim 16 , wherein the saturation mechanism comprises a superconducting coil wound around the first limb within a cryostat.

18. A fault current limiter as claimed in claim 16 , wherein the limiter has a normal operating range of substantially 33 kV to 750 kV.

19. A fault current limiter as claimed in claim 16 , wherein the saturation mechanism is surrounded by a gaseous atmosphere.

20. A fault current limiter, comprising:

a ferromagnetic circuit formed from a ferromagnetic material and including at least a first limb, and a second limb;

a saturation mechanism surrounding the first limb for magnetically saturating the ferromagnetic material of the second limb, wherein the saturation mechanism includes a superconducting coil within a cryostat; and

at least one phase coil wound around the second limb;

wherein the at least one phase coil is immersed in a dielectric fluid; and

the saturation mechanism is not immersed in the dielectric fluid.

21. A fault current limiter as claimed in claim 20 , wherein the first and second limbs are adjacent one another and the saturation mechanism and the phase coil are of substantially the same size or extent.

22. A fault current limiter as claimed in claim 20 , wherein the limiter has a normal operating range of substantially 33 kV to 750 kV.

23. A fault current limiter as claimed in claim 20 , wherein the saturation mechanism magnetically saturates the ferromagnetic material of the second limb during non fault conditions.

24. A fault current limiter as claimed in claim 20 , wherein the saturation mechanism is surrounded by a gaseous atmosphere.