High voltage AC machine winding with grounded neutral circuit

• US 6,891,303 B2
• Filed: 05/27/1997
• Issued: 05/10/2005
• Est. Priority Date: 05/29/1996
• Status: Expired due to Fees

• Current Assignee: ABB AB (ABB Limited)
• Original Assignee: ABB AB (ABB Limited)
• Inventors: Sörensen, Erland, Nygren, Jan-Anders, Leijon, Mats, Berggren, Bertil, Gertmar, Lars
• Primary Examiner(s): MULLINS, BURTON S
• Application Number:
  US08/973,305
• Publication Number:
  US 20020047439A1
• Time in Patent Office: 2,905 Days
• Field of Search: 310179-180, 310/184, 310195-196, 310198-208, 310/213, 174DIG 13- 33, 290/1.R
• US Class Current: 310/196
• CPC Class Codes: H01F 2027/329 Insulation with semiconducting layer, e.g. to reduce corona effect
• CPC Class Codes: H01F 27/28 Coils; Windings; Conductive connections
• CPC Class Codes: H01F 27/288 Shielding
• CPC Class Codes: H01F 27/323 Insulation between winding turns, between winding layers
• CPC Class Codes: H01F 27/34 Special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load losses, reactive currents, harmonics, oscillations, leakage fields
• CPC Class Codes: H01F 29/14 with variable magnetic bias amplitude modulation by means of variable impedance element H03C1/08 ; magnetic amplifiers H03F; circuits for automatic telephonic communication H04M3/00
• CPC Class Codes: H01F 3/10 Composite arrangements of magnetic circuits
• CPC Class Codes: H01F 3/14 Constrictions; Gaps, e.g. air-gaps in magnetic shunt paths H01F3/12
• CPC Class Codes: H02H 3/025 Disconnection after limiting, e.g. when limiting is not sufficient or for facilitating disconnection
• CPC Class Codes: H02J 3/01 Arrangements for reducing harmonics or ripples
• CPC Class Codes: H02K 11/40 Structural association with grounding devices
• CPC Class Codes: H02K 15/00 Methods or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines
• CPC Class Codes: H02K 15/12 Impregnating, heating or drying of windings, stators, rotors or machines
• CPC Class Codes: H02K 2203/15 Machines characterised by cable windings, e.g. high-voltage cables, ribbon cables
• CPC Class Codes: H02K 3/14 with transposed conductors, e.g. twisted conductors
• CPC Class Codes: H02K 3/28 Layout of windings or of connections between windings windings for pole-changing H02K17/06, H02K17/14, H02K19/12, H02K19/32
• CPC Class Codes: H02K 3/40 for high voltage, e.g. affording protection against corona discharges
• CPC Class Codes: H02K 3/48 in slots
• CPC Class Codes: Y02E 40/40 Arrangements for reducing harmonics
• CPC Class Codes: Y10S 174/14 having a particular cable application, e.g. winding
• CPC Class Codes: Y10S 174/20 : Stator
• CPC Class Codes: Y10S 174/28 : Plural semiconductive layers

Abstract

An electric high voltage AC machine intended to be directly connected to a distribution or transmission network (16) comprises at least one winding. This winding comprises at least one current-carrying conductor, a first layer having semiconducting properties provided around said conductor, a solid insulating layer provided around said first layer, and a second layer having semiconducting properties provided around said insulating layer. In addition grounding means (18, 24, 26, 28) are provided to connect at least one point of said winding to ground.

Claims

1. An electric high voltage AC machine for direct connection to a distribution or transmission network, said machine including at least one flexible winding and having a neutral point and comprising at least one current-carrying conductor comprising a plurality of insulated strands and at least one uninsulated strand and a magnetically permeable, electric field confining covering surrounding the conductor;

a first layer having semi-conducting properties surrounding the conductor and being in electrical contact therewith, a solid insulating layer surrounding said first layer, and an outer layer having semi-conducting properties surrounding said insulating layer, and grounding means for connecting the neutral point of said winding to ground.

2. The machine according to claim 1, wherein the potential of said first layer is substantially equal to the potential of the conductor.

3. The machine according to claim 1, wherein the potential of said first layer is substantially equal to the potential of the conductor.

4. The machine according to claim 3, wherein said second layer is connected to a predetermined potential.

5. The machine according to claim 4, wherein said predetermined potential is ground potential.

6. The machine according to claim 1, wherein at least two adjacent layers have substantially equal thermal expansion coefficients.

7. The machine according to claim 1, wherein said layers are adjacent to each other, an each of said layers has at least one connecting surface each being fixedly connected to the connecting surface of the adjacent layer along substantially the whole of said connecting surface.

8. The machine according to claim 1, wherein said grounding means comprise means for low-resistance grounding of the winding.

9. The machine according to claim 8, said machine having a Y-connected winding neutral point and wherein said low-resistance grounding means comprise a low-resistance resistor connected between the neutral point and ground.

10. The machine according to claim 8, said machine having a Y-connected winding the neutral point further comprising a transformer having a primary and a secondary winding and wherein said low-resistance grounding means comprises a resistor connected in the secondary of the transformer whose primary is connected between the neutral point and ground.

11. The machine according to claim 1, wherein said grounding means comprise means for low-inductance grounding of the winding.

12. The machine according to claim 11, said machine having a Y-connected winding the neutral point and wherein said low-inductance grounding means comprises a low-inductance inductor connected between the neutral point and ground.

13. The machine according to claim 11, said machine having a Y-connected winding neutral point, further comprising a transformer having a primary and a secondary winding and wherein said low-inductance grounding means comprises an inductor connected in the secondary of the transformer whose primary is connected between the neutral point and ground.

14. The machine according to claim 1, wherein said grounding means comprise means for high-resistance grounding of the winding.

15. The machine according to claim 14, said machine having a Y-connected winding neutral point and wherein said high-resistance grounding means comprise a high-resistance resistor connected between the neutral point and ground.

16. The machine according to claim 14, said machine having a Y-connected winding neutral point further comprising a transformer having a primary and a secondary winding and wherein said high-resistance grounding means comprise a resistor connected in the secondary of the transformer whose primary is connected between the neutral point and ground.

17. The machine according to claim 1, wherein said grounding means comprise means for high-inductance grounding of the winding.

18. The machine according to claim 17, said machine having a Y-connected winding the neutral point and wherein said high-inductance grounding means comprises a high-inductance inductor connected between the neutral point and ground.

19. The machine according to claim 17, said machine having a Y-connected winding neutral point further comprising a transformer having a primary and a secondary winding and wherein said high-inductance grounding means comprises an inductor connected in the secondary of the transformer whose primary is connected between the neutral point and ground.

20. The machine according to claim 1, said machine having a Y-connected winding neutral point, further comprising a transformer having a primary and a secondary winding and wherein said grounding means comprises a reactor connected in the secondary of the transformer whose primary is connected between the neutral point and ground, said reactor having characteristics such that capacitive current during a ground fault is substantially neutralized by an equal component of inductive current contributed for by the reactor.

21. The machine according to claim 1, wherein said grounding means comprises means for changing the impedance of the connection to ground in response to a ground fault.

22. The machine according to claim 1, wherein said grounding means comprises an active circuit.

23. The machine according to claim 1, wherein said grounding means comprises a Y-Δ

grounding transformer connected to the network side of the machine.

24. The machine according to claim 1, wherein said grounding means comprise a zigzag grounding transformer connected to the network side of the machine.

25. The machine according to claim 1, said machine having a Y-connected winding neutral point wherein said grounding means comprise a suppression filter tuned for the n:

th harmonic.

26. The machine according to claim 1, said machine having a Y-connected winding neutral point wherein said grounding means comprise a switchable suppression filter detuned for the n:

th harmonic.

27. The machine according to claim 25, wherein said n:

th harmonic is the third harmonic.

28. The machine according to claim 1, said machine having a Y-connected winding neutral point wherein said grounding means comprise an overvoltage protector connected between said neutral point and ground.

29. The machine according to claim 1, said machine having a Y-connected winding neutral point wherein an overvoltage protector is connected between said neutral point and ground in parallel to said grounding means.

30. A distribution or transmission network, which comprises at least one machine according to claim 1.

31. An electric AC machine having a magnetic circuit for high voltage comprising:

a magnetic core and at least one winding, wherein said winding is formed of a flexible cable comprising at least one current-carrying conductor and a magnetically permeable, electric field confining covering surrounding the conductor, each conductor having a number of insulated conductor elements and at least one uninsulated conductor element, and inner semi-conducting layer surrounding the conductor and being in electric contact with at least one of the conductor elements, an insulating layer of solid insulating material surrounding said inner semi-conducting layer, and an outer semi-conducting layer surrounding said insulating layer, and grounding means for connection to at least one selected point of said winding to ground.

32. The machine according to claim 31, wherein said grounding means comprise means for direct grounding of the winding.

33. A high voltage electric machine comprising at least one winding, wherein said winding comprises a flexible cable including at least one current-carrying conductor comprising a plurality of insulated strands and at least one uninsulated strand, and a magnetically permeable, electric field confining covering surrounding the conductor including an inner semi-conducting layer surrounding the conductor and being in electrical contact therewith, a solid insulating layer surrounding the inner layer, and an outer semi-conducting layer surrounding the insulating layer, said inner and outer layers forming equipotential surfaces around the conductor, said cable forming at least one uninterrupted turn in the corresponding winding of said machine.

34. The machine of claim 33, wherein the cover is formed of a plurality of layers including an insulating layer and wherein said plurality of layers are substantially void free.

35. The machine of claim 33, wherein the cover is an electrical contact with the conductor.

36. The machine of claim 35, wherein the layers of the cover have substantially the same temperature coefficient of expansion.

37. The machine of claim 33, wherein the cover is heat resistant such that the machine is operable of 100% overload for two hours.

38. The machine of claim 33, wherein the machine, when energized, produces an electric field and the cover confines the electric field so that the cable is operable free of sensible end winding loss.

39. The machine of claim 33, wherein the machine, when energized, produces an electric field and the cover confined the electric field so that the winding is operable free of partial discharge and field control.

40. The machine of claim 33, wherein the winding comprises multiple uninterrupted turns.

41. The machine of claim 33, wherein the cable comprises a transmission line.